1995 Merc 4 cylinder Compression

[sphelps]

The readings were 115,112,112,109 .... Did the test with the motor laying on its side propped up a bit . It was a cold test jumping the starter with all plugs removed and grounded ... Just wondering if these are acceptable numbers ... H/F comp tester ... Hopefully I done it correctly ...

 

[blmccall]

Hi.If the numbers are within 10% of each other they are ok. The motor should be hot when test is done.

 

[sphelps]

Thanks , Checking on this motor for a friend to purchase. did not really have it set up to run and get it warmed up . The owner just repowered to new 4 stroke . He had it out at Thanksgiving and says it runs and idles fine . I figure a cold test is better than no test ... Those numbers should increase with a warmed up motor correct ?

 

[enginepower]

With those kind of numbers on cold engine, I would say it's a safe purchase as long as it doesn't have any unusual noises.

 

[Texasmark]

Numbers are fine. In line with manual recommendations even as you tested it.

 

[sphelps]

Does anyone know what the wot rpm range should be on the model ? It had a 14p prop that was removed and I got a 15p prop for it . Hopefully it will work out ..
btw,,, picked the motor up for 600 bucks ...

 

[CharlieB]

Most motors run within the 4800 - 5500 RPM range WOT.

Prop should be selected to run in the mid to upper end of this range with the boat loaded as normally operated, fuel, coolers, passengers, etc.

Lugging any motor is over-work and to be avoided as it does shorten the lifetime of the motor.