1990 Sea Ray 350 Express Cruiser Compression Test

[Craig Lescombe]

Twin 454 / 7.4 liter engines. Looking to purchase. Survey other than mechanical - passed with flying colours. Sea trial - ran like a charm - 28 mph @ 3200 rpm - both engine perfectly synchroed. Both temp guages @ 165. Ran strong, no missing, no issues. Had my tech perform a compression test - 4 cylinders on each engine - 90 PSI across the board - 800 hours on the engines - my concern was with his procedure - engines were not at normal operating temp - we were under time crunch - sun was going down - not properly warmed up - did one cylinder at a time with all plugs in other than the cylinder being tested - tested with the engine running versus short cranking intervals , meaning ignition wire not removed from coil / distributor - thoughts?

Either his testing was flawed or both engines are uniformly worn / worn out.

Thoughts?

Thank You!

 

[Rusted Nut]

Have him do it correctly.

 

[Thornton69]

Did the engines run smooth in gear at idle? Would think with 1/2 the cyls that low, you would have felt something that may have been a concern. I would question his test equipment and how he performed his test. Sounds like their overall performance was good. Have personally never heard of mechanically checking compression on a running engine. Normally it is done on a warm engine with the throttle plates open. If you are concerned, get a leak down test done before sealing the deal.

 

[Craig Lescombe]

Yes - idles great, accelerates great, overall performance was great. Yes, I am questioning tecnique and test equipment myself. Thanks for the input and I will let you now how it goes.

 

[Phasma]

It needs to be done correctly. Testing it that way tells you little. Ideally a leak down test is best