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1996 mercury force 120hp compression

Accipiter

Active Member
Messages
22
Reaction score
2
Points
42
Boat Make
Sugar Sand
Year
1996
Boat Model
Other
Boat Length
Other
Hey so compression on the motor Are

1-130
2-150
3-150
4-125

What are your guys thoughts on this?
are they good? everywhere i check i get a different answer.
 

RedBarron55

Jet Boat Addict
Messages
280
Reaction score
100
Points
122
Location
Navarre, FL
Boat Make
Jetcraft
Year
1995
Boat Model
Other
Boat Length
16
150 - 125 = 25 psi
15% of 150 is 22.5 psi so the numbers are within the acceptable range.
I would run the engine to warm it up and then check again
10% would be better match.
There is a slight designed in difference between the cylinders
With a charged strong battery all plugs out with the throttle wide open.
Crank the engine over the same number of times.
The gauge should peak out and hold the max pressure in the same number of revs.
Late engines had a compression of 145 top and bottom and 155 in the center.
If this is in the jet boat if it pulls 4800 - 5200 rpm then run it and don't worry about the difference.
A decarb might help.
Do you own the boar or ding a pre buy inspection?
 
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