1981 Evinrude 35hp compression

merc 18xd · #1 January 29th, 2007, 07:53 PM

Hi

I would like to know the compression specs for an 1981 Evinrude 35hp 2-strokes 2 cylinders.

Ands since it's kinda of an old motor what's the lowest compression acceptable.

Thanx in advance.

OBJ · #2 January 29th, 2007, 09:55 PM

Anything above 90psi on both cylinders and within 10 > 15% of each other is considered very good merc. I have had engines run very well on compression in the low 80's and even a little lower on occasion. But the real key is how close they are to each other.

True, when the compression starts getting down below 80, either time for a for a rebuild or new engine.....this in consideration if a good decarbing didn't help and there are no leaks in the head gasket.

DJ · #3 January 30th, 2007, 01:23 PM

Great advice from OBJ.

As stated, the important thing is that they (cylinders) are close to each other.

If you have not done the de-carb process-do it.

It is described in the link below.

I think you'll find the engine is fine, just dirty-inside.

http://forums.iboats.com/bbBoard.cgi...6;gtid=1035563