1991 Evinrude 150 Compression #'s

[akudirka]

Looking for someone to confirm the compression numbers. I ran a compression tester and found somthing interesting.<br /><br />Four corner cylinders measured exactly the same at 84, but the two center ones measured as 145.<br /><br />Is this by design? What should they be?<br /><br />Back ground - Engine was up to temp when tested. Multiple validation tests run.

 

[moderator1]

Re: 1991 Evinrude 150 Compression #'s

Moving to Outboards.

 

[tlove]

Re: 1991 Evinrude 150 Compression #'s

I think there may be some differences year to year on our motors, mines a 93 Johnson. Here's what my numbers are though 90 (+/- 2) on each cyl.<br /><br />I'm testing per Seloc manual instructions.<br /><br />Warm to operating temp, remove all plugs, ground high tension leads (I pull the kill switch), move throttle to WOT, crank through at least 4 complete cycles.<br /><br />Not sure why you need to move throttle to WOT, that's something I don't do on a normal car motor but figured it doesn't hurt anything to do it by the book. You're looking for differences between holes more than a specific reading. In fact my manual doesn't even give what a normal reading should be.<br /><br />Good luck!

 

[clanton]

Re: 1991 Evinrude 150 Compression #'s

If your trust your gauge and methods, remove the heads, you probley will find rough cylinders or bad piston/rings on the ones that read 84, and lots of carbon in the ones that read 145. The numbers should be at least 100 lbs, depenging on model of engine, 145 high for all 150 models that year except for the bass boat engine.

 

[akudirka]

Re: 1991 Evinrude 150 Compression #'s

Per the previous reply sounds like I did the test correctly.<br /><br />Can you clarify what you meant by 145 high on bass boat?<br /><br />The engine I have on there is considered a HO 150 for bass boats.

 

[clanton]

Re: 1991 Evinrude 150 Compression #'s

Not all, but most of V6 engines on the high dollar bassboats that year were Johnson GT, or Evinrude XP engines , They had 35 amp charging, different motor mounts, different cowling, and more, I have heard the 150 GT crossflow made close to 200HP, I have not dynoed one but the ones I have worked run strong if all of the adjustments were right. compression was a little higher also. The 60 degree engine came sometime 1991, had different name, GT and XP were dropped. Compression of 145 is to high for these engine, unless the heads have been cut, DH probley knows a lot more about these engine then I do. I will look for name and spec of 60 degree engine.

 

[akudirka]

Re: 1991 Evinrude 150 Compression #'s

Thanks Claton,<br />Your right on the XP ID, I found it in my owners manual. I also found some hints looking through shop manuals at a relatives house, that anything below 103 is considered a candidate for a new power head/rebuild. Still no specs on what the upper range is.