1997 force 120hp compression

[bogginyota]

While fixing one problem a new problem was found. While fixing the bad stator I found out my compression numbers were not very good. From top to bottom my compression is 142,149,151,151. The motor runs great, but the top hole has me worried about whats to come. If I'm not mistaken they should all be within 10%. My numbers are in spec but getting close to the edge. What is the stock compression of the Force 120, and what is the minimum compression needed to be concidered a good running and reliable engine?

 

[jerryjerry05]

The compression #s on your 97 are a bit different than a older motor.
​I believe the top and bottom cyl are supposed to be lower.
Than the 2 middle ones.
I think they are about 10# difference.

So if it's running and the plugs aren't fouling and burning right??? Run it like you stole it!!!

 

[bogginyota]

Does anyone know the stock compression numbers for the 97 force 120?

 

[pnwboat]

Your compression numbers are pretty good considering the age of the motor. I've worked on many motors which have compression numbers around 120 - 130 pounds and they ran great. I wouldn't worry too much about your compression with numbers that you're seeing for your motor.

 

[Jiggz]

Mind you I got an 89-125HP and my compression tests are barely at 120 PSI! I thought they were perfect readings! LOL

 

[jerryjerry05]

NO such thing as good for it's age!!
​The comp should always be what the engineers designed.

With a good gauge you should get 145-155#
If it reads 120 I'd get another gauge and try again.

I paid $160 for a gauge from the MAC man in 1988.
On my twin 88/85's it reads 145-150#
Still reads that now.

I got a FREE one from the neighbor. "Harbor Freight"
It reads 120.

THE IMPORTANT THING IS THAT THEY ARE WITHIN 5# OF EACH OTHER.
Any more than 5# and I'd be looking for a problem.