1977 85HP Johnson Compression Spec?

[Psycho Trout]

Looking for a little help here. I need to do a compression check on my motor this weekend would anyone know the spec for compression. Thanks

 

[Dhadley]

Re: 1977 85HP Johnson Compression Spec?

As per the factory, there should be no more than 15 pounds difference between the high and low cylinders. No specific number is given as a lot depends on which heads and gaskets are used.<br /><br />Also look at the heads and make sure they are a set. The port head should be 1 digit before the starboard head. IE - *****1 (port) and *****2 (starboard) are a matching set.<br /><br />Good luck!

 

[Psycho Trout]

Re: 1977 85HP Johnson Compression Spec?

Is there a average compression of these motors. I hae lost power in the motor. It takes a couple of minutes to get on a plane. I am thinking compression, but it may be a coil too.

 

[mrc]

Re: 1977 85HP Johnson Compression Spec?

Generally over 100lbs and all within 10% is okay.

 

[sparkroost]

Re: 1977 85HP Johnson Compression Spec?

I have a 77' 85 javelin. 135 psi.

 

[Dhadley]

Re: 1977 85HP Johnson Compression Spec?

Be careful when going for a specific number Mr. PT. There are several head configurations out there and a couple of gasket dimensions for the V4 crossflows too. OMC always went for 15 lbs difference, not a %.<br /><br />Do a compression check -- decarb -- and recheck compression. Lets go from there.<br /><br />Slow down and reread my earlier post. Make sure you have a matching set of heads. Has the motor sat for a while?<br /><br />Good luck!