1976 evinrude 85

[fireman_103]

I cant find my last post on this. I have a 1976 evinrude 85 that has been sitting for a couple of years. I rebuilt the carps put some electronics on it not it cranks and idles on muffs ok. I am waiting for a screen for my water pick up before putting the lower unit back on so I can take it for a test run. Just wondering about my compression about 95 in all four. Ive been told that is ok because there is not a 10% diffrential in measurements. I used the same gauge on a 1987 70 hp evinrude and got around 130 on all 3. Why such a big diffrence?

 

[emdsapmgr]

Re: 1976 evinrude 85

I would say your compression is low for that engine. My overhauled 79 85 hp crossflow runs 125 lbs.

 

[ezeke]

Re: 1976 evinrude 85

The last truly comparable engine in your series [1973-1977] is the 1977 model. Others on this forum have reported very similar compression results in the 90 psi range on motors that ran well, for example:

http://forums.iboats.com/showthread.php?t=190873&highlight=85+compression
​

 

[iwombat]

Re: 1976 evinrude 85

Yep, that's me.

I can report that after the carb rebuild it's running just fine from idle to WOT. I did do a little calibration on my gage against my air compressor's gage and found it to be about 10psi off at 115psi. So, the compression on the motor is more like 100psi. Still, it's pretty close to yours.

So, that was my lesson in not paying attention to the absolute values and only look at the relative values.

My advise: Run it until the performance tells you it's time for a rebuild.

 

[Chinewalker]

Re: 1976 evinrude 85

Also, the 3-cylinder is a higher compression motor - that's part of the reason why it puts out 70 horsepower from only 56 cubic inches. Your 85hp puts out it's horses from 92 cubic inches...
- Scott

 

[fireman_103]

Re: 1976 evinrude 85

Thanks Im gonna run her till she dies just as my 76 115 did.