New To Me Motor. Get More HP?

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imjohnnykelley
Posts: 18
Joined: 16 Dec 2017, 14:34

New To Me Motor. Get More HP?

Post by imjohnnykelley » 11 Jan 2018, 12:34

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.

RazorBaits
water bouy
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Joined: 29 Jun 2016, 19:36
Location: middle of NC

New To Me Motor. Get More HP?

Post by water bouy » 11 Jan 2018, 13:11

At some point they changed 35 decals to 30 when hp was calculated at the prop. So it's probably the same motor already.
16 ft Sea Nymph w/30 Johnson
14 ft Monark w/25 Merc XD sold
1994 Lowe 1605 w/50 Evinrude sold
14 ft Lone Star w/15hp Evinrude sold

imjohnnykelley
Posts: 18
Joined: 16 Dec 2017, 14:34

New To Me Motor. Get More HP?

Post by imjohnnykelley » 11 Jan 2018, 18:05

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

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Pappy
Donor
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Location: Central Florida

New To Me Motor. Get More HP?

Post by Pappy » 11 Jan 2018, 19:30

The "change" happened in 1984. Engines were rated at the propshaft instead of the crankshaft. Your engine is indeed what used to be a 35hp already.

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Ebug
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Joined: 31 May 2013, 15:51
Location: Boerne, TX

New To Me Motor. Get More HP?

Post by Ebug » 11 Jan 2018, 20:02

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

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Bowhunter1661
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Joined: 05 Sep 2012, 18:43
Location: Chicago Suburbs, Illinois

New To Me Motor. Get More HP?

Post by Bowhunter1661 » 12 Jan 2018, 08:21

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”.

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