Modding a 40HP Johnson to a 50HP

[Metalhead Fisherman]

Hello all,

I am looking at a 1996, 40HP Johnson outboard that's in great condition, Only problem is I really wanted a 50HP as its the max HP my boat calls for and I'm going to be adding some more weight to it over the winter when I deck it out more into a bass style boat, My question is the guy I am buying this off ran this by me about converting it to a 50HP. I have researched it and see that the 40/50/60 HPs Johnsons are similar and I just wanted to see what some peoples opinions are.on it.

What type of conversion is this specifically as well if anyone can add that in.

Thanks!

 

[Bosunsmate]

i doubt its very easy, itd need rejetting new manifold probably too and probably much more, i dont know.
What i do know is that a 40hp with good compression will be better than a 50hp with poor compression

 

[flyingscott]

If you are already looking at doing something like that you are probably better off waiting for a 50 hp to come up fore sale. I have not heard to many people say my boat has to much power I have heard a lot of complaints about being under powered.

 

[gm280]

I'd say if you take the three versions of your engine (40HP, 50HP and 60HP) and do an in depth part number search for all the differences between them, you will see what it will take to conversion yours. I honestly don't think it is a mere carb swap or something like that. Port timing and other internal things have to be different. And the fact that the engine power heads and casings should prove that out. If all the part numbers between all three are the same, then there is no difference between them. But you know that isn't correct. So start comparing the part numbers and see... JMHO!

 

[Metalhead Fisherman]

That's the thing GM, where I have read about this guys have said the components are the same on the 40/50/60 Johnsons cept the carbs, you also gotta change the jets?

 

[gm280]

That's the thing GM, where I have read about this guys have said the components are the same on the 40/50/60 Johnsons cept the carbs, you also gotta change the jets?

I suggest you go to a web site called "boats dot net" and type in your engine under the Johnson manufacturer and then the year and HP and start printing out the break down diagrams with part numbers. That way YOU can see the differences. If it turns out that the only differences in part numbers are the carb or jets, then that is all there would be to change the HP. But I'm thinking there is a little more then that... JMHO!

 

[ondarvr]

You can't trust what somebody's cousin's sister overheard at a bar ten years ago, you need to look it up yourself, you'll need to do that anyhow to make sure it's made into a 50 correctly.

Unless you have both motors (40 and 50) already the cost is normally higher, and the hassle factor much higher, than just buying a 50 to start with.

 

[Scott Danforth]

its on the internet..... It has to be true..... Bonjour.