# compression on 15 hp evinrude



## walleyehunter78

What should the compression on mid 80's to mid 90's 15 hp be? Are the 15 hp johnsons the same exact motor as the rudes? Looking at buying one and want to know. Also should i be taking compression on a warm or cold motor. If there is anything else these motors are notorius for that i should look for, let me know. Thanks


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## crazymanme2

Good compression is around 140 but me personaly wouldn't let it be lower than 120.Pretty sound & same motors


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## walleyehunter78

I looked at a 91 15hp rude today, and it had 115 on top cyl and 110 on bottom cyl cold. Decided to pass.


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## crazymanme2

There will be a good one that comes along.Be patience.


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## Whoopbass

I have bought many 15 hp JohnnyRudes the past few years and none of them had more then 110 lbs psi. They all ran good. 
My 25 hp motors have always been around 120 lbs psi.
The guys over on iboats say about 100 lbs psi is good for a 15hp but they will run fine in the 80 lb range.


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## crazymanme2

They may run good with 80 - 100 # compression but they won't have the get up & go that a 15 should have.A brand new 15 has 140#.I personaly wouldn't touch a motor that is under 120.There's too many good ones out there to mess with the junk.


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## Whoopbass

Like I said I have bought a lot of 15's and have never come close to 140 psi so apparently there isn't to many good ones in my area. :lol: 
I think if WalleyeHunter is waiting on a motor with 120+ psi he might be waiting a long time. That 91 he looked at would have been a good motor that probably had 20+ years of life left in it.


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## jasper60103

Keep in mind some compression testers are not all that accurate. I had two that had drastically different readings on the same motor.

edit: I'm just saying I wouldn't condemn a motor based off of one compression reading, or at least confirm the accuracy of the compression tester. Just my 2 cents.


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## Pruitt1222

Outboards arn't my bread and butter, However two stroke chain saws are. On a saw 160-140 Is new, 140-120 is used in good shape, 120-100 is still usable but much reduced proformance. And anything under 100 is bad, Cant keep plugs clean, smokes alot, hard to get started, will stall much easier, and way reduced on power. Note, Most outboards are two cylinder and chainsaws a single. I do know a saw will not run under under 85psi and is super hard to get started under 95 psi, Once you get the piston rings and cylinder up to temp it will pop but that may take 20 pulls of the cord. Just keep in mind this is my experance from two stroke singles, A twin will be slightly different. A motor running 90 on one piston and 100 on the other should run fine after you get her going, just won't be long till a rebuild.


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## crazymanme2

Pruitt1222 thanks for the backup on my thinking. =D>


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