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Compression Test HELP

S

Sydison

New member
Im looking at purchasing a boat 330 SeaRay Sundancer and the port engine is new ( has 60 hrs on it ). I had a compression test done it and it is as follows.

Cylinder PSI
1 130
3 140
5 110
7 140
2 135
4 140
6 120
8 130

The mechanic who did the test stated since the engine was so new that the two cylinders that showed lower PSI ratings were probably not fully seated yet or broken in. Can anyone please help in clarification on this test and if there is any truth to that statement ?

I appreciate any help in advance
 
What year is boat/engine?
What engine size is in boat? 5.7, 7.4?

Typically you should see minimum 150 psi in a V8 possibly 160-170

110 is very low
 
without knowing any further details, here's one opinion....

The test results show the engine is serviceable, per GMs current recommendations regarding compression tests.

I'd throw the BS flag on your mechanic's assumption - he should have added some oil and verified his assertion....I believe 60 hours is plenty of time to have the engine get to "fully seated"....
 
kghost said:
What year is boat/engine?
What engine size is in boat? 5.7, 7.4?

Typically you should see minimum 150 psi in a V8 possibly 160-170

110 is very low
Click to expand...


I though the same on his comments.

The engine is 5.7l 3540 Mercruiser. The engine is a crate engine placed in the boat last year.
 
makomark said:
without knowing any further details, here's one opinion....

The test results show the engine is serviceable, per GMs current recommendations regarding compression tests.

I'd throw the BS flag on your mechanic's assumption - he should have added some oil and verified his assertion....I believe 60 hours is plenty of time to have the engine get to "fully seated"....
Click to expand...

I agree...........


after 60 hrs you should have virtually equal psi across all 8 cylinders......+/- 10 psi
The numbers you posted would be for a well used engine about ready for rebuild
 
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