1981 90HP Evinrude vs 1982 115HP Johnson

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Pat Crowley

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Oct 19, 2009
Messages
23
I sure hope someone can help me. I have a 1981 90HP Evinrude with a blown powerhead but it looks great. I also have a 1982 115HP Johnson that runs good but is ugly as sin. Just looking at the two, they look almost identical. I have looked up the piston numbers and they are the same for both motors as is many other parts. Why is one rated 90HP and the other 115HP. Is the cylinder displacement larger on the 115 or is it a gear ratio thing or what. Maybe Evinrude and Johnson just rate engins differently. Can I take the 115HP powerhead and put it on the 90HP lower unit. Physically, I'm pretty sure it will fit. I'm probably going to try it soon so if anyone knows of a reason not to, please respond as soon as possible. Thanks
 
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ezeke

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Sep 19, 2003
Messages
12,532
Re: 1981 90HP Evinrude vs 1982 115HP Johnson

You can swap the powerheads complete. The 90 is ported differently and has different carburetors. The 90 probably has a flatback exhaust whereas the 115 may have a bubbleback exhaust.
 
trendsetter240

trendsetter240

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Jun 22, 2009
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1,458
Re: 1981 90HP Evinrude vs 1982 115HP Johnson

Pat Crowley said:
I sure hope someone can help me. I have a 1981 90HP Evinrude with a blown powerhead but it looks great. I also have a 1982 115HP Johnson that runs good but is ugly as sin. Just looking at the two, they look almost identical. I have looked up the piston numbers and they are the same for both motors as is many other parts. Why is one rated 90HP and the other 115HP. Is the cylinder displacement larger on the 115 or is it a gear ratio thing or what. Maybe Evinrude and Johnson just rate engins differently. Can I take the 115HP powerhead and put it on the 90HP lower unit. Physically, I'm pretty sure it will fit. I'm probably going to try it soon so if anyone knows of a reason not to, please respond as soon as possible. Thanks
Click to expand...

I can help with a couple of these...

No rating difference, Evinrude and Johnson engines are identical.

Yes, the powerheads are interchangeable. They both have the same mid section and gearcase.
 
Chinewalker

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Re: 1981 90HP Evinrude vs 1982 115HP Johnson

Both are flat backs. The difference is in carburetion and porting. The 140 got the bubble back.
 
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emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 1981 90HP Evinrude vs 1982 115HP Johnson

The 115 hp that year also had the 140 intake filler blocks behind the reeds. Probably good for 3-5 hp.
 
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