New To Me Motor. Get More HP?

Hey there. I just bought an 1989 30HP Evinrude Long Shaft 2 Stroke. Doing some rebuilding and working on it. Read on an old feed here of someone upgrading their 25 Johnson up to a 35 with just a carb change out. Is it worth it? From what I gather I should be able to bump mine up to at 35HP carb pretty easily. What would I need to get to do that if it is doable? I am good with small engines, but the world of outboards is a little new to me, so figured you guys could help me! Thanks for the info.

At some point they changed 35 decals to 30 when hp was calculated at the prop. So it's probably the same motor already.

water bouy said:

At some point they changed 35 decals to 30 when hp was calculated at the prop. So it's probably the same motor already.

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So what you are saying is, outside of a lot of work, I aint getting any more power out of this baby. Haha. Dang. Was hoping for a cheap and easy upgrade.

I normally start my research into questions like this by going to an online parts supplier and start comparing part numbers between the engine I have and the next hp size up.

When I did that for my Johnson 40HP I found that all that is needed to make my engine meet the 50HP mark is to change the reeds/reed cage and carburetors. I'm sure there will need to be a jet change in there too.

I looked at your engine and it appears there was a 30hp & 35hp that year. Both have identical cranks, pistons, carbs, reeds/jets...so you have what you have. The 40hp engine above yours is a different block completely.

Rob

I had a 1988 Johnson 25 not too long ago. In my research i found the difference between a 25 and 35 was the intake size, both the throat size of the intake and the overall internal dome size. Your motor should already have the 35 carb on it. When I had that motor i did change out the 25 carb to a 35. My motor for some reason already had the larger intake so i didn’t have to mess with that. That motor ran like a bat out of he[[.

I believe the difference between 30 and 35 is the throat size of the intake. As long as you have the larger bore carb you should be able to simply use a dremel or rounded file and enlarge the throat opening of the intake. You would have to look online at jet sizes. If the jets are the same part number from 30-35 then your golden. If it is a different part number between the two you may need to open the jet up a little. Say .001”-.002”.