COMPRESSION ON SPORT JET 90

[TOOSTROKIN]

HAVE A QUICK QUESTION. WHAT IS THE NORMAL COMPRESSION ON A 94 SPORT JET 90 HP. I HAVE READINGS OF <br />#1 120 PSI<br />#2 120 PSI<br />#3 120 PSI<br />IS THAT NORMAL FOR ALL 3.<br />MOTOR HAD 557 HRS AND RUNS GREAT.

 

[roscoe]

Re: COMPRESSION ON SPORT JET 90

120 sounds good, but suspect, because they are all the same.<br />Should have been in the 135 - 150 range when it was new.<br /><br />Did you have all three sparkplugs removed when doing the test, or just from the cylinder you were testing?

 

[TOOSTROKIN]

Re: COMPRESSION ON SPORT JET 90

I TRIED IT WITH ALL OUT FIRST AND THEN WITH THE OTHER 2 IN. BOTH TIMES GOT 120 PSI.

 

[eurolarva]

Re: COMPRESSION ON SPORT JET 90

Motor should be tested after it has been running awhile. Also at wide open throttle. In order to do this you will have to disble the neutral interlock switch in order to test it with the electric starter. Also when you do this you should have the spark plugs out and grounded with the spark plug wires connected. Make sure the lower unit is in water so you dont damage the impeller. Your test results are probably okay. Hard to say how accurate your tester is. If numbers dont improve and you are confident that your compression tester is accurate try doing a decarb then testing again.