Introduction: Making New Marine Vinyl Boat Seats

About: Just a normal guy who enjoys the water and outdoors. Grew up on the water in the Panhandle of Florida fishing and boating, still live on the gulf today just a little further Southwest.


Finally got a little time to do some work so I made new seats and motor box for the back of the boat.  The plywood for the original motor box and seats was rotten to the the core so everything had to be rebuilt including new plywood, cushions, and vinyl.  This is how I did it, take note, this is my first time sewing vinyl and I have not sewn since I was a kid so bear with me. 

So this is one of my installments on restoring my 22 foot aluminum Sylvan boat.  The boat is an inboard outboard so there is a padded motor box in the back with a custom sized jump seat on each side of the motor.  The vinyl all throughout the boat was pretty much shot so in my ultimate wisdom I decided to take on the project and redo the interior.  Heck, I sewed back in middle school, what was that....  25 years ago...... I figured piece of cake.

Step one was to get a sewing machine so off to craigslist I went.  $35 later I had a Singer 237 cast iron beast but in Italy in the early 60's and the thing has no problem chomping through eight layers of marine vinyl.  So after about two weeks of sewing practice I figured I was ready to go so let's get started on this project!

Step 1: Procure Materials!

Well we now have the sewing machine so what else is needed?  A lot, I will try to compile a list

Marine Vinyl (ebay has this pretty cheap)
Marine Thread (Bonded Polyester in the V69 size is recommended)
16 or 18 gauge ball point needles
Pre-Made cording
Foam (Joaans fabric with 50% off coupon is not too bad on price.)
Plywood for the bases (more on plywood below)
Stainless Staples and staple gun
Paint for the plywood (I used some old leftover white)
Circular Saw (to cut the plywood)
Sander (plywood again)
Electric Carving Knife (for cutting the foam)
Scissors (Cutting the vinyl)
Measuring Tape
Double Sided tape
Zipper foot for sewing machine

I am almost sure I missing something, before you ever start do a lot of research, some good internet resources for marine sewing are and the forums at 

Now, on plywood.  There are many grades of plywood, some say marine grade is what you need, others say pressure treated.  Here is what I found with research:

1. Marine Grade - This could be many types of softwood glued together with exterior waterproof glue.  Marine grade is not treated for rot, it must be kept dry somehow (paint) and will rot.  What makes marine grade is the waterproof glue and lack of voids within the layers, this provides superior strength for structural components like transoms of a boat.
2.  Exterior Plywood - This wood made from many different materials uses a waterproof glue like marine ply but the quality of the wood is much lower.  There will be voids and these days the quality of the wood is pretty darn low.  I used Southern Yellow Pine CDX for this project, a 1/2" sheet cost me $13 vs about $50 locally for marine ply.
3.  Pressure Treated ply - This plywood is treated against rot, caution must be taken when using any treated wood due to the toxic chemicals involved.  This plywood is basically cheap exterior grade ply that is then treated for rot and insects.  This wood is relatively cheap about $25 a sheet but usually comes wet so expect warping and twisting as it drys if not frames tightly.

For this project I went cheap with CSX exterior plywood and chose to paint it with exterior latex house paint, two coats.  Since this wood is not structural to the boat and Southern Yellow Pine is about five times stronger than the fir used in Marine ply I should be fine. Now on to the instructions.

Step 2: Framing the Box

We are gonna skip the seats since I was using a crummy camera for the seat construction.  The seats are identical to the top of the motor box so consider it the same only smaller.

So the box was built out of 1/2" plywood in two pieces, a three sided lower portion joined to the floor and transom and the top with is three sides with a top that will flip forward to access the engine. The entire box is covered with vinyl with a cushion on the top. The top portion of the box was probably ok to reuse the wood but I replaced it anyway.  The lower portion of the box being on the floor of the boat got wet much more often and was rotten in the corners and other areas. So... using the old box for measurements I started my plan.  I had Home Depot cut the plywood into strips along the length of the panel to make it easier to move and reduce my cutting needs since I did not have an eight foot saw guide.  So I really only had to cut these pieces to length.

To assemble the box I frames some strips of pressure treated lumber about 1"X1.5" I had lying around and used 1" staples and tightbond II waterproof wood glue to hold it together tight.

Once assembled I did a rough sanding to remove splinters and break the edges for the vinyl.  Once sanded I put two coats of Sherman Williams exterior latex paint over everything.

Once the glue was set these boxes are very sturdy and once they are joined to the boat this thing is going nowhere!

Step 3: Vinyl Time!

So once the box was done I measured the top and sides, the bottom required no sewing just a strip of vinyl oversized to wrap around it. The top of course needed to be boxed with some cording to make it look nice.  

So when sewing a seat there is the top and the box.  The top is self explanatory the boxing is the skirt hanging down over the sides.  I really cannot properly describe everything involved in sewing this so please do some additional research if you undertake this project.

First the top was made to be 1" oversized in both directions, this allow 1/2" for sewing on all sides, this matched the size of my cording.  So the first step in making the box is to sew the cording to the top.  Since my sewing machine does not have a walking foot I used a lot of double sided tape to hold the cording on the vinyl and ensure both layers feed at the same rate.  You can see in the pictures just sewing along. Around corners I notched the cording to make is curve without binding or twisting.  I used a 4mm stitch size which is the largest my machine will do.  Smaller stitching will actually reduce the strength of the seam in vinyl so use the largest your machine can.  The tricky part is at the end of this run, you need to take once side of the cording and remove about 1" of stitching and cut the cord out of it.  You then need to tuck the other side of cording and trim it to the length of where you cut the other cording out, then fold the first side vinyl over the tucked side and stitch it closed to make a nice joint.

Now that the top is sewn we need to add the boxing.  Easy right?  Wrong!  This is the tricky part especially with the long boxing required for this motor box.  I wish I too more pics here but I was pretty angry half the time I was doing this and forgot to take the pics.  Start out with lots of double sided tape and start sewing, remember you are going through four layers of marine vinyl here so you may have to motivate the machine at times to get things started.  When you start the boxing leave about six free inches dangling before you start sewing, you will need this when you have to sew the boxing closed at the end.  keep sewing until you get about six or eight inches from the end. Once you are here near the end you have to sew a seam to close off the boxing.  So pull it together and see where the two sides will meet and then sew that seam, once the seam is done finish the top seam on the cording.  Caution when you are finally finishing the boxing you are probably at the samepoint you tucked the cording which means you can be sewing through up to eight layers of vinyl, coupled with the immediate transition from four layers to eight makes for tough feeding so be sure you lower the foot pressure on the machine and proceed slowly, by hand if necessary.

So you have your vinyl done, lets go to the install now.

Step 4: Cutting Foam

So cutting foam, my method is to measure, mark with sharpie, and cut with an electric knife.  I oversize the foam about a half inch on every side to make sure the cushion is nice and stuffed.  For the box top my 24" wide foam was not enough so I had to glue another piece of foam to make it wide enough.  Be sure to glue factory cut lines as the knife will not cut a straight enough line to glue cleanly.  Once the piece is formed glue it on the top of the box, I used 3m spray foam adhesive bought at Joaan's once again with a 50% off coupon.

So we have the cushion on top so it is time to add some batting on the sides.  The batting will provide a slight amount of cushioning on the sides of the box and give it a fuller look so you cannot tell it is a plywood box.  I just cut the batting to rough size and glue it on with the loctite adhesive and trim once it is in place.

Step 5: Stapling Vinyl and Bringing It Together

Wow! Home Stretch!

So stapling vinyl, what can I say but you will build some serious grip strength doing this.  I used a standard staple gun and stainless staples.  The boat maker did not use stainless originally and they were rotted away.  Here in Florida we cannot use non-stainless hardware so spend the $10 on the box of staples and rest easy they will last.  So for stapling the vinyl just keep pulling, stapling, and tucking. I start with a single staple on opposing sides and work away from them.  

Once an entire piece is stapled trim it close for a clean look.

Step 6: Finished Product

So here we have the finished product, what a labor of love, two seats and a motor box.  Please feel free to ask questions.

Watersports Summer Challenge

First Prize in the
Watersports Summer Challenge