Surf Bike is a lot of fun and the closest thing to walking on water.

After using Surf Bike for more than 10 years, water got inside the casing through the seals around the propeller shaft and the pedals axle. The information here was not available anywhere so as I made the repair, I took pictures and documented the repair steps to help other Surf Bikers.

Step 1: Removing Seat Post and Pedals

Seat post is held in place by a larger bolt and nut and 2 smaller screws near the top of the yellow casing. Remove all 3 screws.
Pedals must be remove using the Pedal Extractor supplied by Surf Bike or equivalent available from any bike shop.

Step 2: Opening the Pedals Casing

Place a roll of duct tape under the casing so that the pedal shaft can go through it and maintain the casing in horizontal position, with the LEFT side of the casing at the bottom (important because the propeller is captive of the LEFT half).
Remove the 19 screws that hold the 2 halves of the casing together.
Slowly ease off the Right side of the casing that is now held in place only by the seal around the pedal shaft.

Step 3: Removing the Chain and Tensioner

Remove all grease from the contour gasket.
Measure the position of the chain tensioner before removing it so you can put it back in place with the correct tension. Mine has a 14mm space between the tensioner housing and the rectangular washer.
To clean all components and replace the seals you must unscrew the bolt holding the chain tensioner in place.
To make sure you install the pedal gear wheel in the same position later, tie a small wire around the right end of the pedal threads before you remove it, as shown in the picture. In theory, both side should be the same but this is a way to play it safe.
Once the chain tensioner is removed you can remove the pedal gear wheel and clean it.
Clean the chain and the propeller shaft. I used a tooth brush dipped in Varsol and wiped it off with a rag.
Using a good bearing grease, apply new grease of both sides of the 2 bearing wheels and make sure the pedal gear wheel turns smoothly in the bearing wheels.
Clean the contour gasket.

Step 4: Removing the Propeller Shaft

The propeller shaft is held in place by a pin going through the chain gear wheel on the shaft.
Position the propeller section of the casing on a strong flat surface like a piece of wood that will not damage the casing while you hit the shaft pin with a hammer.
Using a punch of small nail, hit the shaft pin making sure it does not exit too far from underneath and damage the casing. Once most of the pin is out of the shaft, finish removing it using a vise grip to pull it out of the shaft.
Once the chain gear wheel is loose on the shaft, slowly use the propeller to turn the shaft and slide it out of the casing and notice the position of all components that slide off the shaft.

Step 5: Removing the Propeller Shaft Seal

Using a small flat blade screwdriver, push out of the yellow casing, the propeller shaft seal.
The original seal on my Surf Bike is enclosed into a metal casing which is good to protect it from debris that might get stuck between the propeller and the casing.
There is enough space in the casing to add another seal under the original metal encased seal.
The replacement seal that I found is embossed with the following markings = Taiwan TCM 03072TC - 6 but it was sold to me for $6.18 each as part nr S0037500750-250TC from www.sealsonline.com

Step 6: Cleaning the Empty SurfBike Casing

Now that all components are removed from the SurfBike casing is the right time to clean it all.
I used a tooth brush dipped in Varsol to loosen all the dirt from the inside and all came off easily with rags without damaging the casing.
Using a small flat blade screwdriver pushing a clean rag, I delicately cleaned the contour gasket so that it can properly seal once assembled.

Step 7: Pedal Shaft Seal Replacement

Pedal shaft can be displaced using a flat blade screwdriver.
The original seals on my SurfBike has markings embossed on it = NAK 17 35 7 4 www.nak.com.tw is the manufacturer of this seal, www.dichtomatik.us is their distributor in the USA. In Quebec, Canada where I am, I paid less than $5 each seal equivalent = S017035070TC that were in stock at an affiliate of Dichtomatik = Les Joint Etanches R.B. 8585 Henri-Bourassa Ouest, St. Laurent QC, H4S 1P7 Tel : 514-334-2220 and they are affiliated with www.sealsonline.com
Push the new seals in place and you are ready for the re-assembly.

Step 8: Propeller Shaft and Assembly

If you need to replace the propeller or the shaft, notice the once you remove the 2 surface screws in the propeller, you will have access to the pin that holds the propeller in position on the shaft.
While the propeller is on a strong but smooth finish surface, use a punch to push out the retaining pin.

Step 9: Installing New Propeller Shaft Seals

Notice the 2 seals on the left side of the first picture.
Insert the new rubber only seal (part nr S0037500750-250TC) in the bottom of the tubular casing section.
Insert the old original metal encased seal on top of the other seal, with the metal facing the outside, to give it mechanical protection.
The end result should be like in the other picture showing the metal encased seal positioned flat with the edge of the tubular section of the propeller casing.

Step 10: Installing the Propeller Shaft

Using white Lithium grease or equivalent on the propeller shaft, slide it through the seals while sliding on the shaft each shaft components detailed on previous pictures.
Make sure you install the chain on the chain gear wheel before you slide it on the shaft because you will not be able to install the chain on it later.
Position a piece of wood under the propeller section of the casing so that you can hammer the pin through the shaft.
Using a magnifying glass, notice that the propeller shaft pin is tapered at one end; insert that end into the chain gear wheel and hammer it down until you get close to the chain. To avoid hitting the chain I used narrow tips pump pliers to pressure the pin into the wheel for the rest of the way until it was flat with the wheel on both sides.

Step 11: Installing the Pedals Gear Wheel

IMPORTANT = the chain must go from the top of the propeller gear wheel to the FRONT of the pedals gear wheel. This will ensure that when you pedal forward, the propeller will push you forward, not backward.
Install the chain tensioner and position it as it was before = mine has a 14mm space between the tensioner housing and the rectangular washer.
Put white grease on the right side of the pedal gear wheel before you install the right side casing half on it.
Using Dry Lube or equivalent, lubricate the chain, the pedal gears, the propeller shaft gears and holders.
Using White Lithium Grease or equivalent, lubricate all the contour seal and flat sections of the casing.
Place the Right side of the casing through the right side of the pedal shaft seal and push it against the left half of the casing.
Secure together both half of the casing with the 19 screws around the contour leaving the 2 top screws loose to allow inserting the seat post later. Note that only the Right side of the casing has washers in it and it is through that side that all screw heads go so then all nuts are on the Left side of the casing.

Step 12: Install the Pedals & Seat Post

Considering that the propeller is the back of the unit, make sure you install the pedal with an R engraved on it on the Right side of the casing and so on for the left side.
Insert the pedal arm on the pedal shaft and push it in place with a rubber head hammer enough so that you can install the nut on the shaft. Place the plastic cap on top.
Slide the seat post as far as it will go and install the post securing bolt through it.
Tighten all screws and check that the propeller turns freely when you pedal.
Using a trash can filled with water, dip the bottom of the SurfBike in it and turn the pedals for a while.
Remove it from the water and move the casing from side to side; if you do not hear water moving inside the casing, you have successfully repaired your SurfBike.