Well, there are a lot more fleetwin experts here than I, but I have two neutral clutch models, 50 & 53 and a full gear shift 58 model. The 58 is a beautiful running motor that I just love, but it is really not a power house. It will not plane a boat with me and my son in it. If he is alone, it will plane the boat, and then it will move along OK. The neutral clutch motors will plane the boat with both of us in it. We even ran them both at the same time as twins. That was FUN!

Steve

Fourteen inches is definitely too low. The standard transom was supposed the be 15" vertically. Since the transom angle standard was 12 degrees, the distance along the transom was almost 17". I usually ran a 17" (vertical measurement) transom, putting the "cavitation plate" half an inch below the running water line. Most speed gains on outboards is finding the correct propeller for your boat and load.

However you do have a design problem in your Fleetwin in that the connecting rods have bronze bushings. The factory compensated by increasing the oil in the bronze bushing 5 & 7-½ horse motors. They did it by giving those two smaller 4 gallon fuel tanks. The bigger motors use the 6 gallon tank. Adding the recommended quart of oil gives you a 24 to 1 ratio for those bigger outboards. They have needle bearing connecting rods and run very nicely on that ratio. That same quart in a 4 gallon tank gives you a 16 to 1 ratio to better lubricate the bronze bushings.

When they booted the output to 8 HP, they did it by putting needle bearings on the connecting rods. Later models gained some by tuning the exhaust and improving the combustion chamber. A lot could be done to increase the output of your Fleetwin, but it would be more economical to just buy a bigger motor.

Skip the modifications. Find a bigger motor. A 10 or 15 will do the trick without risk of stressing the motor. Those 7.5s have a nasty habit of ventilating the crankcase if you push them hard (or skimp on oil). A 10hp of similar vintage should not be hard to find…

Your 1954 Fleetwin doesnt use modern roller bearings in the powerhead like newer outboards. It is critical that you stick to 16-1 mix. I use 16-1 on all my older motors and none of them smoke much using Mercury premium plus oil. As for a prop. I would use one off of a 5.5hp Fisherman . It has less pitch and will help the motor rev up with a heavier load. Plus it should be easy to find one pretty cheap… As far as elevating the height of the motor. I doubt it will make much of a difference at the speeds the 7.5 is capable of on your boat.