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MERC 98 COMPRESSION SPECS

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duff3

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"Help, I have a 1979 mercury 9

"Help, I have a 1979 mercury 9.8 that has been sitting unused for about 10 years. I don't know what the compression should be normally on one of these. I have about 60 psi on a wet compression test on both clyinders. I am concerned that since it has sat in my grandfathers garage unused all these years that the ring maybe frozen up. Any thoughts or ideas would help. I have not tried to start it yet, I wanted to check all basic first. Thank you"
 
"get some marvels mystery oil

"get some marvels mystery oil in there and let it sit over night, u might free it up

also are u opening the throttle all the way?"
 
have 78 150 black max merc 85

have 78 150 black max merc 85 compression test on all cyl is that good ?
 
"JC,

No that is not good at

"JC,

No that is not good at all. It might run, but I doubt if it will run very well or very long.

Tony"
 
my boat is 78marlin with 21 st

my boat is 78marlin with 21 stainless prop runs excellent in water 5500 rpm sounds good starts right up can you tell me why 85 psi isnt good? and why my boat runs so well? and how to get my copression up were needed thanks
 
Throttle position has nothing

Throttle position has nothing to do with compression on a two stroke. The exhaust ports are open to supply air for the compression test.
 
1978 black max 150 runs really

1978 black max 150 runs really well but has low compression 85 psi on all dont know what to do holds 5500 strong with 21 stainless with passengers my first boat and i want this motor to be superb this summer should i leave it at 85psi or take it higher at recommended 130-150psi and if i take it to 130 how much more power will the the motor put out please help john
 
step #1 is to check your compr

step #1 is to check your compression gauge or have someone else do a test.There may in fact be nothing wrong with the motor.
 
TO not a student you were righ

TO not a student you were right used a different gauge and all cyl were 100 thanks john
 
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