Re: 1991 Force 120 hp L-Drive HELP
yes you shoudl have at least 125psi --to maybe 150psi (depending on the gauge used)on each cylinder. But the most important thing is the actual pressure measured during a secondary compression test is the variation from cylinder to cylinder. On multi-cylinder powerhead, a variation of 15 psi or more is considered questionable. On single cylinder powerhead, a drop of 15 psi from the normal compression pressure you established when it was new is cause for concern.
To try and fix your problem Seloc recommends
1. If compression readings are lower than normal for any cylinders, try a "wet" compression test, which will temporarily seal the piston rings and determine if they are the cause of the low reading.
2. Using a can of fogging oil, fog the cylinder with a circular motion to distribute oil spray all around the perimeter of the piston. Retest the cylinder. If the compression rises noticeably, the piston rings are sticking. You may be able to cure the problem by de-carboning the powerhead. If the dry compression was really low and no change is evident during the wet test, there is evidence that there is internal damage or excessive wear to the cylinder or piston. The cylinder head needs to be removed for further inspection
3. and Lastly, If two adjacent cylinders on a multi-cylinder engine give a similarly low reading then the problem may be a faulty head gasket. This should be suspected if there was evidence of water or rust on the spark plugs from these cylinders.
hope this helps
