The Surly Mermaid: Catamaran to Recreational Cruiser Conversion




Introduction: The Surly Mermaid: Catamaran to Recreational Cruiser Conversion

About: Retired Jr. High science teacher of 30 years. Always into lots of things. Now I seem to be into them more. Love woodworking, guitar, portrait painting, and a lifelong obsession building things. I have rotat...

Video of Maiden voyage at the end.

Note: This instructable may seem rather randomly assembled. It was such a long process that I added to it periodically as I worked on the boat instead of writing it up at the end. So, instead of it being broken into chunks of like items, it is in chunks as It progressed chronologically. i.e. Each block of time I worked on it I jumped around to different things. It's written that way. It's sequenced in the way I worked on it.

Also, In my quest to be as economical as I can and a definite awareness that I don't know everything, I'm sure there are alternative ways of accomplishing some the the things I've done. But, at this time, these were my solutions to the way to get it done.

Long ago, I published and instructable here called "The incredible soda bottle pontoon boat". That was in 2006. In the instructable, I updated it later on to show improvements and in the last entry, it's demise, as I dismantled it after a number of years.

Well, I've done it again. This time it's different. As much as I liked the "barge" as we called it. It was like a floating island that moved at about 2 mph. We enjoyed it though, and it was fast enough for trolling. This new endeavor is svelter. I don't think it will go much faster but will move with fewer batteries and fewer electric motors.

I've been looking for a larger sailing catamaran for a few years. I checked craigslist often. What I was looking for was two fold. One, an 18 ft or longer catamaran. Lots of 16 ft ones around but I wanted more buoyancy. Two, I preferred a 'fixerupper'. I preferred something older but in good floating shape. Maybe with missing sails or hardware like the mast. I would rather repurpose something that would probably never be used as a sailboat again instead of cannibalizing something good. I looked at a few like this but they were in too bad a shape to put effort into. Structurally unsound. Eventually I found a catamaran that was old but in pretty good shape in Cape Cod. A 1971(ish) 18 ft Solcat. Not made any longer. And, the price was better than excellent. The disturbing news was that it had all hardware/accessories in tact. It could have been refurbished as a sailing catamaran. Being a bit older and having looked a fair amount of time, I decided I would repurpose it for 'me'.

One thing about the Solcat is that it was a bit heavier than catamarans later on. This was a plus. Lots of catamarans today have thin hulls to keep the weight down. Nice for sailing, but they can lose integrity after awhile. This Solcat is sort of a beast. The hulls were intact, had been painted a couple of times, and had a couple of soft spots on the decks. Nothing too bad though. There was also some minor delamination where the deck crimped over and connected with the hull. Time to make it more seaworthy.

Step 1: Prep and Primer

The first thing I did was to unbolt the pontoons from the frame and turn them over. This gave me better access to the business side. After a ton of sanding using a rotary sander with a course grit sandpaper any holes and major dings were taken care of with body filler.

Using body filler on these pontoons could be a mixed blessing. I didn't want to get out the fiberglassing stuff. Messy and there weren't any major cracks. I settled on body filler but I decided to use it conservatively. The pontoons will give with pressure. They are a bit flexible. Body filler isn't. I did have some deeper scratches and a couple of gouges but putting larger spreads of body filler might prove problematic. It can be brittle. If the filler cracked, it might even chip down the road. Since the pontoons were 44 years old and although in good shape, they have seen some wear. I decided to not go overboard trying to smooth them out in fear of overdoing it and having the filler chip off later on. When things where dry I used my Random orbital air sander to smooth it down using 240 grit paper. The sanding dust was washed off with a power washer and the pontoons wiped down with a damp rag of xylene to remove any other residue.

I used Rust Oleum marine above deck primer and paint. They do make a below waterline paint but researching online I found that in fresh water, the topcoat is plenty durable. And it comes in better colors and is much less expensive. Even though, the color choices weren't too agreeable to me. I decided on the navy blue. The royal blue was to, well, blue. The other colors weren't on my radar of what I wanted. I'm hoping it's durable enough. I'll be taking the boat out each fall so I'll be able to touch things up if need be.

The primer went on with great difficulty. I was using an HVLP sprayer with an 80 gallon compressor. This primer must be very good. Even though I had it shaken in the store a day before, when I opened the primer it was almost like putty with a one inch oil layer on top of it. Stirring the quart can was nearly impossible. I was going to thin it with xylene but first I needed to get it out of the can at least a little stirred. After breaking a couple of stirring sticks I had made I took an old 7/8" spade drill bit and ground off all the points and sharp edges. I used it as a paint stirrer in my cordless drill. After awhile I got the primer to pour but it was thick and lumpy. After straining it the best I could I added about 5% xylene to the quarter of a quart I poured into a can and stirred it some more. While spraying I had to clean the gun at least six time before the primer coat was on both pontoons. This was a very difficult process. The only solace regarding this is that the primer must have lots of solids. So, it will probably stick good. Good paint, hard to work with.

Step 2: Topcoats

The primer went on flat. The topcoat is more glossy. If you'll recall, this is Rust Oleum marine topcoat paint. I knew I would be putting on a few coats. I was spraying with and HVLP sprayer. It tends to 'dust' the surface. The upside to it is that it's hard to get it too thick. This helps to avoid thick spots and runs. The topcoat paint was so much easier than the primer. It was thick and creamy and after thinning with about 5% xylene, it sprayed very nicely. The first spraying, it actually was pretty much a dusting. The second coat the next day filled in the color more. The third coat finished the job after a very light sanding to take off any roughness.

I must say that the gloss of the topcoat does show any imperfections more than the flat primer did. As I said before, these 44 year old pontoons are going to have their age marks. I chose to flatten them minimally instead of loading them up with brittle body filler.

Step 3: Deck: Part A

The rear of the pontoons are about six inches lower than the front. I determined this by leveling the trailer and subsequently the forward end of the pontoons. The back half sweeps downward. I was not quite sure just how low in the water the back end would be so I decided to attempt to level the deck by raising the back end of it 5 1/2 inches.

I did this by cutting off sixteen inch pieces of 2x6" framing lumber and sandwiching it between two pieces of plywood. After a bunch of exterior teflon coated deck screws it will be very stable.

The wood chosen was pressure treated lumber. The big box stores are loaded with it here especially in early spring like it is now. Everybody uses it as it holds up to Maine winters (and summers). The good qualities are it will never rot in the application I'm using it for. It's not expensive (I'm constantly trying to keep costs down, it's a thing with me), and it's strong. The downsides? Well, it's heavier than regular framing lumber. They use southern yellow pine and it's wet with the compounds they infuse it with. It will dry over the summer and get a lot lighter, but a standard spruce 2x4 that they sell around here feels like styrofoam compared to this stuff.

The deck, at this stage consists of ten and twelve footers. I will be cutting them to make a more rounded five facetted front. It will hang out over the end three feet at the maximum point which is the center of the deck.

I originally wanted to attach the floor to the cross beams with very large 4" and 5" U-bolts. I was going to bolt a galvanized angle Iron piece to one side of the 2x4 just above the cross beam then mount a U-bolt under the cross brace and into the angle iron. That would have really snugged it down. I still think this is the best idea but after looking at the cost of all of the hardware for this, eight sets, front and back the cost would have been between $80 and $100, so I looked for another alternative.

At the box stores they have lots of galvanized straps in the lumber area. They are fairly bendable. I found that by attaching them to the wood and saving the inside screws as the last ones, it pulled the straps snug against the pipe, almost like a clamp. Each of the joists is tight. I might still put a couple of U bolts in the back, just for luck. Not sure yet.

The end joists present their own problems. I want them close to the ends of the cross beams but there's no place for a strap. I'm toying with the idea of loosening the beam bolt that attaches it to the pontoon and slipping a thin strap under the beam, then screwing it to the wood like the others. We'll see.

Step 4: Deck Veneer

It’s starting to take shape a little. Today I cut up some sanded plywood to veneer the sides of the deck. I’m painting them first on the inside and out to help protect against the water and weather. Behr paint from HomeDepot. It’s pretty much all we’re are using around here now for outside paint. It seems to last longer than anything else we’ve tried. Didn’t use it for a long time because it costs about half of other good brands. Whodathunk it was so good.

The veneer plywood is put on with galvanized finish nails (nail gun whenever possible). I used some filler on the small holes. Later on I’ll put another coat of paint on to cover them and make it look flatter. On the back piece I used screws as it is also structural to hold the floor beams in place better. I also cut the contour of the front and have two of the veneers drying on plywood at this time. I’ll assemble them onto the boat tomorrow.

Also, my bilge pumps came in today from Amazon. I’ve got two. One for each pontoon. Now I think the pontoons have pretty good water integrity but they aren’t like a fiberglass ski boat. The walls are much thinner, made that way to keep the weight down for sailing. If I were to get even a small hole in one it would fill with water and not be good. The pontoons are built with about 50% styrofoam in each one, but that’s only to keep the boat afloat should it tip over while sailing. It’s no longer a sailboat. I need it to float. Not ‘just’ stay above water. Each bilge pump is submersible in water waterproof electrical fittings. I’m going to assemble a tube in each of the rear top screw on caps at the back end of each pontoon. You can see the caps in one of the pictures above. The tube will attach to the output of the pump that’s in the pontoon. Two wires will also extrude from the cap and lead to switches in the console. The pumps shoot water as fast as a water hose. I’ve seen them in action. So, unless I get a big hole in the bottom I should be able to make it home, or at least to shore before going under. Of course the pumps will also be good to bail any incidental water that gets into the pontoons over time. A pontoon isn’t an open boat, so bailing with a bucket isn’t an option.

Second day on this part and after finishing the veneer, filling the nail holes and it's finished. I also installed the center pipe for wiring.

I also installed four galvanized angled brackets to the edge joists. I couldn't put a strap because the crossbeam was on the pontoons. This angle should hold them.

Step 5: Deck: Part B

A small interim step here as it was done in this order.

Pressure treated plywood on the deck. It's on now because the treating process leaves the wood very wet and heavy too. It will be painted with a latex light grey porch and deck paint but I need to leave it in the sun, hopefully it won't rain much or I'll have to cover it. After it is thoroughly dry then it will be primed and painted. Also, the plywood has to be fitted and screwed down within a couple of days of purchase because when wet pressure treated plywood dries unsecured, it does some major buckling. Then it's hard to work with.

The plywood is 1/2" thick and I'll want to put a 1 1/4" vinyl edging on the perimeter so the edge is thickened with strips of pressure treated wood cut down to 1/2" and screwed to the deck, bringing the total thickness to one inch. The vinyl edge will be fashioned by fitting together two vinyl siding starter strips. That will be made clearer later. First the drying, then the painting, then the edging.

The vinyl edge will hang down a 1/4" to hide RGB LED strips that will be glued under the deck edge and shine down onto the white sides.

Step 6: The Console Shell

It's raining out and the deck is drying so working on the console is in order.

The console will be where all the controls and other items will be housed. It will set in the center front of the deck up over the metal crossbeam, so about 24" behind the center foremost part of the deck. I had originally made a sort of traditional squarish and stylized console but after it was done I decided it was too cumbersome for the small, svelte surface of the deck. This one is simply three front panels tilted back about fifteen degrees.

In it or on it will be housed:

1. two 12 volt batteries, one atop the other on shelves.

2. Fuse box, ground strips

3. AM/FM bluetooth automotive radio with weather shield and a whip antenna mounted outside the console.

4. Fish finder.

5. Five speed rotary electric motor switch.

6. On/Off switch for the second electric motor.

7. Weatherproof toggle switches for various lights, bilge pumps, etc. and a variable touch switch for the RGB strips

8. A momentary DPDT toggle switch for steering. I'll be using a linear actuator as a steering mechanism. More on that later.

9. Digital Volt/Amp meter, USB and 12 volt ports.

10. Two battery switches, One for each battery.

11. A dual charging 20 amp marine battery charger with external RV plug to plug the charger into shore power.

All of this stuff is in a big box from a previous Amazon order. And yup, About half of the build cost is in this console. Gee I hope it doesn't sink!

As you can see in one of the pictures all holes have been cut to accept equipment and switches.

As you can see in the pictures 3/4" plywood was cut so angles would make a slightly tilting console with flared sides. Braces help it stay together and to be able to screw it together from the inside. Glue was used of course. When things were roughed in I put my usual coat of paint on the entire thing, inside and out, anticipating some sort of moisture getting on and into it at some point. After it is complete, it will get some filler for screw and blemish spots a final coat of paint.

Step 7: Console, Finishing Up

Today I got out and mounted the console controls and instruments after a final coat of paint.

On the left are two red battery switches. I want to be able to turn on one battery at a time or both together. I could have gotten an off/batt1/batt2/both switch but they're all pretty big. These are smaller. Another battery switch is on the right. But it's used to switch on the second electric motor. Next to it, the big black knob is a rotary electric motor switch, 5 speed forward, three reverse. Switches in a line for lights and bilge pumps have rubber waterproof boots on them. The separate switch in the center is a momentary on/off/on switch. It will be used to steer by activating a linear actuator (more on that later on).

Along the top left to right, volt/amp meter, rgb light control, USB port, fish finder.

I've also included a picture of the underside of the console and the location of the dual connection battery charger. Two AGM batteries, both inside the console, one on the floor and one on a shelf above it.

On the side of the console is the AM/FM antenna for the radio and speakers you see mounted on the front and a socket to plug in an extension cord for the charger.

Notice on the charger picture the T nut. When the front panel is put on and the control panel is put on top of it, a single screw holds the two together. An aluminum L tab holds the bottom of the front panel on (first picture)

Note: Three switches are not installed in these pictures. They're on order from Amazon at this time.

Step 8: Bilge Pump Assembly

The bilge pumps will be mounted in the rear most well caps on each pontoon. I've chosen some small DC submersible bilge pumps that do about 800 gpm. They don't have any automatic switches. I'll have a manual switch on the console for each one.

An enclosed pontoon will be difficult to empty should any water get into them. I'm assuming the pontoons are pretty well sealed but I want the option of draining them without having to get in there with a cup to do it. These pontoons do have a drain plug in the back end of each one so I assume that water somehow does seep in.

When I go to Lowes or Home Depot and I'm building something like a boat, all I see is potential boat parts. Here I found this expansion fitting It is threaded on one end and the 3/4" pipe extends in or out and has two sealed o-rings. I needed to extend about 8" to the bottom of the pontoon. This would allow me to extend it till the pump sat in the bottom of the pontoon.

I drilled into the pontoon screw in cap and mounted the threaded part of the extension through the opening and screwed the fitting on the top side of it with silicon in between to seal it. After mounting an elbow to the lower end then bilge pump will be connected to it using a very short length of rubber hose and clamps. The top extends, via a 3/4" pvc pipe 9" long to an elbow. This top extending elbow will be positioned aft to expel water in the wake.

Another small hole in the cap will contain a 1/2" pvc pipe and elbow. This pipe will provide an exit for the power wires from pump and provide an air intake as this little pump is quite fast and air intake is needed to relieve pressure.

The final picture shows them installed in the rear well of each pontoon.

Step 9: Float Test, Added Buoyancy, Deck Primer, Trailer Additions

At this stage, the wife and I took the platform down to the boat launch to see how the buoyancy was fairing. Good and not so good. Floatation was pretty good. When I got on it it still was fine but when I moved to the rear of the platform the rear of the pontoons move down near water level.

I had anticipated the possibility of this. Yes, yes, I know that I used some heavy wood on the platform, but honestly, I built it to try to balance cost, weight, and stability. I wasn't going to spring for aluminum and regular wood would be rotted out here in Maine after a couple of years. The pressure treated wood was used as sparingly as possible. And, it has yet to completely dry which will alleviate some of the weight. All plywood is 1/2 inch with joists spread apart a bit.

So, it could work okay this way. The pontoons are sound and sealed. But, I'd like a little more buoyancy. I anticipated this possibility. I've seen a guy on Youtube make a smaller catamaran conversion and he added a plastic Kayak down the center. I've had one bookmarked from Walmart for awhile in case I needed one. It's 8.6 feet and has a weight capacity of 295 lbs. and the price is fairly good. I don't know if it's a good Kayak, doesn't matter as I just need it as a third pontoon. So, (next day) we went over to the Walmart and picked up the Kayak. It's a sit on not a sit in, so it can't fill with water. It's basically a flat plastic tube with a dent in the top for your butt. I hoisted it up with ratcheting cargo straps then strapped it up with some nylon (the plasticy type, not the cloth type) strap and used screws to the deck to hold it in place. After I realized the cargo straps were the thing that was really binding it in place, so they stayed where they were. It's solid. Not much fun working beneath the boat but it got done.

Since the plywood was dry I managed to get a coat of latex primer on the deck. It had been raining on and off and I've been waiting for it to day.

Also of note, I welded together some extended guides like on pontoon boat trailers. I mounted them then covered them with PVC pipe to prevent them scratching the pontoons. I needed these as the rear of the boat would wander when I tried to put it on the trailer. When I last did the test launch it worked great. Also, I had one side roller missing. It was missing when I bought it. So I again welded up a roller mount and since I didn't have any hard rubber tube but did have some swim noodles. I fashioned a section of noodle for a roller. It works and will probably last long enough. I can just replace it for about a buck.

Note: I also temporarily mounted the motors on the frame I welded up for them. This was to get measurements for the steering mechanism. These motors are two of four I had when I had built the soda bottle pontoon boat years ago. They are 35 lb. thrust minn kotas'.

Step 10: Deck Paint, Edge Banding, Bimini Mounting Brackets

Today I managed to get a coat of latex porch and deck paint on the deck. It's a light grey and should compliment the blue/white colors of the rest of the boat. After it was dry I put the edging on the deck. Again, trying to keep costs manageable I opted for a double piece of vinyl siding trim. By using two of them inserted one inside the other I managed to get a double rolled over look. The added advantage is that they come 12 feet long and are available at big box stores. As you can see in a couple of the pictures, I fit them together in a way they weren't met to fit together. The idea came when I looked at them in the store. Seems they ship doubled up like this. It looked good so voila. I used a hair dryer on high to bend them to the shape of the deck. I installed the top one first using pan head screws then laid down some clear silicone with a caulk gun and pressed the other piece in place from the bottom up. Masking tape is used to squeeze them together till the silicon dries.

The bimini top is a relic from my old pontoon boat (see link in first step of this instructable). It's a little too big. Years ago my sister sewed it up for me. Good job with basting along the edges and all. It's Sunbrulla. A brand type that was a bit pricey but supposed to be fairly impervious to a lot of things, UV, mold, etc. It was out and up for eight years in the weather and you can see the shape it's in. I'll have my other sister alter it later.

I welded up two brackets to hold the poles. The brackets are mounted with lag screws and bolts to the center of the right and left edge of the deck. From the brackets three poles will rise. One facing aft, one vertical, and the other facing forward. It will become clearer when I actually raise them and slide the canopy on them. I had this setup on my first boat so I know it works.

Off tomorrow to purchase nine 1" galvanized metal electrical conduit pipes, elbow sweeps and a few other items to get this made. Last time I purchased these for the other boat years ago they were $2.90 each, now their $9.90. I was told that they were going up soon because of the steel tariffs taking effect soon as of this writing. So, doing it now.

Step 11: A Little Wiring, a Little Lighting

A lot of the wiring happened this day. I previously had run a length of 2 inch pvc pipe down the center of the boat to the back, popping through the rear. The front end of the tube is what will be underneath the console up front.


Wire is so expensive. I wanted to do it right but wanted to keep the cost down. The two main pairs of wire for each motor are 4 gauge jumper cables. This stuff is a lot per foot, but if you purchase it in the form of 16 foot jumper cables the price comes down dramatically. So, two 16 foot jumper cables. One for each motor will run from the switches (and batteries) in the console. I also found a 100 foot coil of #14 speaker cable on Amazon for a very good price. The remaining control cables for the motors, the linear actuator for steering, and the wiring for the bilge pumps will be this wire. Connectors for a lot of this will be male/female crimp connectors both for easy connection and easy removal if need be.


The rear navigation light is an old one I had left over from a previous build. The front red/green navigation light came from Amazon and is mounted on the nose. Just beneath it is a 12" LED bar head light. Not needed much but it comes in handy when docking at night. I learned this from my previous boat build. All LED to minimize current draw off the battery and for longevity.

Step 12: Fish Finder Transponder, Actuator Cover, and Pole Holder

Today saw the installation of the fish finder transponder. I've picked up a Garmin 4cv fish finder. The transponder will be mounted forward center right in front of the console. I've mounted a pvc pipe within a pipe that will slide up and down to raise or lower the transponder. A 'T' fitting is on the end and the transponder is connected to ti with two band clamps, much like you'd do if you mounted it to an electric trolling motor. A pin holds it up or down and a notch in the outer pipe at the top that the pin fall into aligns the tube so that the transponder is always facing forward.

Also saw the installation of a cowling for the linear actuator used for steering. The actuator is meant for solar installation and is supposed to be fairly weatherproof but it didn't look that convincing to me. Simply a short section of 4" wide plastic pipe slid over it and anchored with a zip tie so it doesn't move with the actuator rod.

Next a pole holder. The metal pipe mounted through the rear of the deck is covered with a convoluted concoction of pvc fittings to make two angled pole holders. I didn't glue them, just put aluminum screws through the fitting joints. On the center pipe, between the pole holders, will reside the second switch to use for steering from the rear of the boat.

Step 13: Installing the Bimini

I had previously welded up steel brackets to connect bimini top piping to the deck. It's a metal plate with a U shaped upright plates. Three holes are drilled each above and forward of the other. Each hole holds a 3/4" EMT electrical pipe (Homedepot) The pipes connect to the bracket with 1/4" bolts washers and a plastic washer/spacer cut out of some pvc board with a hole saw. The holes are each higher than the previous one so that when the pipes are retracted to the rear they will lay on each other.

To connect the pipes together I use 1/2" conduit sweeps that are fit inside the pipes. A small screw holds them in. Actually there is enough pressure when done for them to stay by themselves but if something should lift the top, maybe a big wind, they won't come out.

The rear pipes will be permanently lifted at an angle. of about 45 degrees and held up by pipes slid into a drilled hole in the deck and pinned with a bolt through the side of the boat. The front pipes are held forward taught by bungie cords.

The bimini, as I mentioned in a previous step was from my previous pontoon boat. Sunbrella, good stuff. This one needed narrowing so off to my sister with a sewing machine to cut it down to size. The cloth has large loops on each end that the pipe goes through. A 4" section of 3/4" PVC pipe is sliced down the middle and cupped over the cloth and upper joint on each of the three sections. A screw holds it in place. This is put on to make sure the cloth doesn't ride up over the tops of the pipe and to assure the center riser pulls forward and stays in place when the top is put in place.

It's not made like and doesn't look like the bimini on a regular pontoon boat but it's simple and it works. Very sturdy. Like on my other boat, I'll pretty much leave it up all summer.

Step 14: A Boat Name and Tunes

Light at the end of the tunnel.

My order for decals came in the other day. The choice of names was from my daughter. She's always envisioned a boat named "Surly Mermaid". So, I accommodated her on this one. Besides, it is a cool name. The font I chose is very 'mermaidy' in my mind. It's very ornate but I don't know if it matches a very homemade platform boat. But when I saw the font I realized it had to be the one. A little tricky to put on but not too bad. The company promises a free redo if you mess up. Once on it looks like a thin layer of paint. I had made a stencil and tried to do it myself. Unfortunately, even when using temporary spray on glue the wood grain still caused bleeding, so I abandoned the task.

Note: The name is also seen, in a camera pan, on the animated Disney cartoon "Finding Nemo". It's a boat in the harbor outside the dentist's office. And it's also the name of a restaurant someplace, as found on the internet.

I had ordered a $24 car radio. I wasn't looking for spectacular sound or quality, just some radio tunes and maybe something from an SD card. Alas, I should have known. I probably had a 50/50 chance of it working out. It didn't. DOA when I tried it out. Something with the multiple wire socket I think. possibly it's the soldering on the circuit board. I managed to get it to flicker a couple of times then gave up after trying to work on it.

I had in my possession a small class D receiver/amplifier I had toyed with a year ago. It had amazingly good sound for it's small size, is stereo, and will take an SD card or USB drive. After connecting it to the automobile speakers and powering it temporarily, I found that it worked and worked well. A couple of machine bolts and it was installed. I cut the 12volt connector off an old dead power brick and wired it to a fused port in the console. Pretty good sound. More volume than I should use on the water and I get all the local FM stations any other radio gets around here. And, I paid about $20 for it. It's much better quality than the car radio.

The radio is housed in a marine radio cover. A flip down door protects the unit from the elements.

I'm getting close to a launching date.

Step 15: Launch: the Maiden Voyage

Today we launched. After taking two days to get a homemade boat registered in Maine I'm exhausted. I had to get a registration number (like a VIN for a boat). They issued one from the state department. Then I had to engrave the 12 digit number in two different but specific places. I had a dremel but my dremel penmanship isn't very good, then pictures of my work and calls to the state dept. Finally I got the number to put on the bow.

The launch went well. I don't have pictures of it because it was a busy day at the town boat ramp. People were lined up and waiting. It slid into the water nicely and the buoyancy was satisfactory. I had to leave the canopy retracted from the trailer ride to the ramp because we had a large road tunnel to go through to get to the main part of the lake were our home is. After that we raised it as the sun was pretty hot. I brought lawn chairs for myself and the wife.


I once had a heavy homemade pontoon boat with four electric motors. It was slow and lumbering but it got us there. The speed of a moderate walk. Good for touring and trolling. The Mermaid is lighter but it only has two electric motors. The same ones I used on the other boat. Half the weight but half the power. The result is about the same speed. Both boats don't do that good in a headwind. This one is lighter though and it's easily turned by the wind. And as luck would have it there were unusually heavy winds on when I launched it to drive it home.Nearly whitecaps on the water. And to add to that, to get home we had to head into the wind all the way. Home was north and the wind was coming in from the north. We hugged the shoreline where it was much calmer and did okay. This maiden voyage had clear waters in the video above.

Periodically I would check the level of the rear of the pontoons. They didn't seem to change. I also periodically turned on the pumps to see if any water would come out. It was dry. That's good news. I was hoping that I had sealed things up pretty good after all my efforts to do so. I'll keep an eye on it as it's docked over time to make sure I don't wake up to a partial submergence.

Things I need to do:

Nothing is pressing to get done on this at this time. When I pull it out in the fall I plan on changing out one of the motors. I have four motors. Two that are long and two that are short. I used the short ones as if I had used the long ones they would have stuck up about two feet. The reason for these lengths is that I had removed the heads and cut them to fit under the previous boat I had made long ago. The two short ones fit on this boat nicely but one of the motors was somehow cut a bit shorter than the other. I have it as low as I can get it but when I sit in the middle of the boat it can cavitate as the boat rocks with waves. The end of the prop breaks the surface and sputters. Propulsion can't be good then. I'll have to cut down one of the long motors and mount it a few inches lower than the current one.

I've ordered my second battery. I had only purchased one as it was all I needed to wire the thing and test it out both on land and the water. I had always planned on two batteries. I've learned from the past 'One battery used to go out and when that drains it's time to turn around and use the second battery to make it back'. While we were out today I timed it and we took about an hour and a half to get home. It's a six mile lake. The boat ramp isn't that far but the boat is slow and the lake is long. And that nasty, strong headwind most of the trip. How strong was it? A life preserver and my wife's hat blew backwards into the lake while traveling and it wasn't because we were going fast! The voltmeter is connected with a shunt across the negative terminal. It's designed to read under load. Today I end up, under load with a voltage reading of 11.67 volts. The current being drawn by the motors was about 41 amps with both motors running full. I've got a sealed 100 amp/hr AGM deep cycle battery. When I removed the load it jumped up to about 12.35 Volts. Good batteries. I've got one like it in my camper. I can't seem to discharge it much.

The linear actuator used for steering works really well. Not fast but fine if you're not going fast. I did notice that as the strong wind tried to catch the sides of the pontoons and turn us I had to continually correct and sometimes it was strong enough that I had to overcorrect to get it in the right direction. Calmer waters shouldn't present this issue.

Step 16: Slowly Adding a Few 'in Use' Images/videos


The Mermaid goes good. I've got a rear cap leak in one of the pontoons. After about 3 hours of cruising I have to use the bilge pump. It collects about a gallon of water. I'll soon remove it and find a way to seal it better. Not a big issue and water only gets in when I'm on the boat and it's moving as the rear dips under water sometimes only at that time.

Maybe I've uploaded enough pictures of bass and perch. A bunch were from 2 hrs of trolling.

More to come....?

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    9 Discussions

    I just sold a cat that I was making into a trimaran. There were two long hauls 4 original cat which was made out of a sailboat period ever fiberglassed and needed completing for flotation.
    If the current owner does not want them they are long enough for a 28-foot boat.


    4 weeks ago

    Great job! If there isn't a prohibition to gas power on your small lake, a little 2.5-5 hp outboard would be a much better propulsion unit. I don't think I'd put anything over a 5 hp on it though. Of course you just may not want anything fossil fueld, which is fine! An electric outboard might be the ticket, but electric outboards are expensive... unless you order directly from China....

    Note that the cheap Chinese motor DOES NOT come with the 48V, 1000W/24AH battery (batteries?) needed. Four 12V in series would work though.

    Otherwise they are around $2000 for a 3 hp, but those typically include a battery.

    1 reply

    No plans for anything else. My two 35 lb thrust minn kotas are just fine. On our lake you can start fishing right from the dock. No particularly better place. And in this warm weather right down the middle 60-90 ft of water is great for bass at about 15 feet down. On my two (yes I finally added my second battery) 100 amp batteries I can go about 3-4 miles down the lake and back. Takes awhile but I love the scenery here in Maine. Slow but perfect trolling speed. Three bass yesterday. Thnx for the comment.

    If you ever do need to use the bilge pumps, as it is, you may have a vacuum problem. In order for bilge pumps to actually work, you need to have a vent for air to replace the water, as the water is pumped out. Not much is needed as air will travel faster thru a vent than water will. You can use small diameter pvc pipe, and have it curled over to protect it from any waves, rain, etc. You can also use an end cap that can be removed as needed.

    1 reply

    You're right. If you look at the last paragraph in step 8 you'll see mentioned that I have a 1/2" tube coming up out of the rear cap for the wires and to act as an intake vent. That tube is open at the end, and out of the water as it enters the under boat deck. I did put some water in the pontoons and then evacuated it to see how it worked. And it works good. Those little pumps really push out a lot of water. Thanks for the comment.

    Nicely done. Good sailin' to ya.

    This is so great! I love seeing the processes of boat building. :D

    Thank you. I tried to include all the steps but know that it does jump around a bit. The only thing you didn't see was the rats nest of wires in the console. It got out of hand after awhile. Amazing I only blew one fuse after turning the power on.