How accurate is a compression test on a cold motor??

[crazy charlie]

1992 150hp cold compression test

How accurate can a compression test be on a cold motor? Boat I want to buy is in indoor storage.Boatyard said they cant get to it or cant get water to it until late March/early april.I want to know NOW if compression is good and all within proper range.If I did a cold compression test ,I should still be able to determine if the readings are within the proper percentage of difference??? Correct?? Charlie

 

[crazy charlie]

Need to do a pre-purchase compression test.Marina has boat buried in indoor storage with no water until April.Want to buy now.How accurate would precent of readings difference be on a cold motor?? Charlie

 

[ezmobee]

I'm no expert but I'd think they'd at least show you the difference between the cylinders which is the most important thing anyway. I just did my Evinrude cold and got 110,110,110,100 which seems pretty legit.

 

[tpenfield]

The compression numbers should be a bit lower than if you did it with a warm/hot engine and the variations may be a bit more, (5-10%) . . . But . . . If you are just looking for ball park go vs. no-go kind of numbers it should be OK. If you are looking to test for conformance to spec, then you want a hot engine for testing.

 

[crazy charlie]

Yes,I want to do the test myself and assume the difference readings should be pretty accurate all things being measured cold.I also assume the actual compression #s will be lower especially on an older motor.Cold may actually give me a better idea of the amount of wear.I think??

 

[crazy charlie]

Performing compression test on cold motor

Need to test the health of a motor to see if I should pursue.At this time no option of running the motor.I assume compression reading would be lower that if warmed up properly but percentage of cylinder difference should be accurate..?? How much can I tell from a cold compression test??

 

[jbcurt00]

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