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Mixed up Fastwin

F

Frankenstein fastwin

New member
Hello everyone,

I just joined the site and this is my first post.
I have a 1969 Evinrude Fastwin. It is my first outboard so this is all new to me. I bought this motor a few months ago and I replaced the plugs, points, condensers, coils, and wires. I also rebuilt the carb and replaced the impeller. I've got it running pretty good.

I decided to decode the engine I.d. number on the side of the motor and I realized that my before I bought it someone replaced the power head with a 1973 25hp. The engine code is 25302a. Whoever did this used all the parts off the 18 to make it work. It has the mag plate and flywheel off the 18 and the carb and intake. It runs pretty good but I was wondering if it would be worth trying to find a carb off a 25 to put on it. Does having the 18 intake make a carb swap pointless? Do you think it makes any more horsepower than the 18 did?
My real concern is should I be worried about having a "FRANKENSTEIN" motor? Does it hurt anything to have these mismatched parts?

Thanks for your time.
 
Do you know if they put the inner exhaust tube from the 18hp on the 25hp? Other than the intake manifold those are the only two parts that may cause a fuel flow issue. Replace the tube and manifold and you can safely put the 25hp carb on and gain a few ponies.
 
Your right I was looking at the wrong part all he needs is the intake manifold and carb and it should be just fine. Definately rebuild the carb and confirm the high speed jet size. Clean/rebuild the fuel pump and replace the fuel lines.
 
I'm not sure if it has the exhaust tube. I will check it out. Is it difficult to do the intake swap?
Do the reed valves have to be swapped out too?

Thanks for the advice.
 
OK. I'll try to find a carb and intake. There aren't a lot of boat shops in my area so parts are scarce. Do you know of any places to find the carb and intake besides ebay?

Thanks for all your help.

One more question-are the 25 and 18 the same displacement? What are the differences besides the intake and carburetor?
 
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