45 and 47 PSI Mariner 9.9 HP

[inlandlake]

I have a 1992 Mariner 9.9 HP(serial number 0c268922) with 45 and 47PSI found recently by mechanic. The motor ran fine and would start on the first pull run at full spead for about 30-45 seconds and then bog down but start up easily again and do the same. The mechanic that looked at it rebuilt the fuel pump and cleaned the carb but could not believe the motor ran . I took it out last night and the boat ran great gets up to speed and stays running. HOw could a boat with such poor compression run so well . Should I do anything else? Should my boat even run with this low compression. Thanks for all of your insight

 

[flyingscott]

I doubt your compression is that low.

 

[Dave1027]

That may be normal for that motor. The many smaller motors were designed with lower compression to make them easy to pull start. That's about the same comp number as my old Johnson 3 hp. Even brand new they were only about 60 PSI

 

[QBhoy]

I’d suggest that your mechanic’s gauge is way out of calibration and/or leaking.
The cynical man, might even think that your mechanic could be changing his arm, in the hope of getting himself a hold of a now very sought after machine, for a bargain price perhaps. Why don’t you buy yourself a cheap compression tester and have a test of it yourself. If you were actually that low on compression, on both cylinders, it would be slow to start and feel pretty asthmatic too. 100 psi or more, would be ideal on that engine. With close figures between the two.
Benefit of the doubt, might be that the rings were sticking..
Lovely engine you’ve got there. Carb clean will be all it’s needed or needing.