1989 Force 125hp outboard compression test

[rachel51970]

Can anyone tell me for an 89 Force 125hp outboard what the compression test range should be in? I bought the repair manual but it doesn't provide the chart to advise what is acceptable or not.

 

[brianvolt7]

Re: 1989 Force 125hp outboard compression test

My 90 Force 120 with an 89 125 top end has a low of 117 on the number three and ranges up to 123 on the number one. Numbers two and four are both at 119. I don?t know what factory specs are but I have heard if you are within 10 psi between them all you should be OK.

 

[pnwboat]

Re: 1989 Force 125hp outboard compression test

Approximately 100LBS to 150LBS would be typical minimum and maximum readings. Having said that, I've seen motors that have 75LBS that seem to start and run well but they lack the power when you put a load on them like trying to pull a slalom skier or maximum payload.

 

[shakazulu]

Re: 1989 Force 125hp outboard compression test

My Force 125 89. has 120-130 psi in all cylinders. But I am thinking about decarbonising motor, maybe I could get more compression

 

[JB]

Re: 1989 Force 125hp outboard compression test

Hi, Rachel

Welcome to iboats.

There is no spec for psi. Gauges, conditions and techniques vary too much. The same engine can compress 125psi with one gauge and tester one day and 75psi the next day with a different gauge and tester.

The important thing about a compression test (see instructions in the Engine FAQs Forum) is that all cylinders compress withing 10% of each other.

On a 4 cylinder engine like the 125 the chances that all four cylinders would fail at the same time and by the same amount is not worth calculating. If they are equal (+/-10%) I call it a good engine.

If all 4 tested at, say, 50psi, I would declare the gauge and/or test procedure bad, not the engine.