What are the minimum deliverables you'd expect for a Compression Test

[hfschwing]

I recently had my engines(twin 6V92s) compression tested and was wondering what the common practice is in the reporting of the test results. How much or how little data is provided the customer by professional diesel mechanics? Is there a standard?

Thanks

[rustybucket]

Rule of thumb: Be crystal clear of what you are expecting up front.

[hfschwing]

Rule of thumb: Be crystal clear of what you are expecting up front.

Yes- I asked for a written report before starting and was promised a written report. But after the work was done nothing was provided and waffling that usually no report provided... so my question was what was "normal" if there is such a thing. What is the minimum a reasonable mechanic would provide? Other than a verbal "low". Are there other useful parameters obtained in a compression test other than a psi. Since this was my first compression test I was unsure and why I have asked the forum.

And before you say I should have not have paid... my boat had been held hostage in the yard for three months with numerous other work performed most of them which were ever so slowly completed I had to pay to liberate it! Had no reason to believe that the compression test results would not be provided as promised in some written form.

[Avenger]

The manufacturer has a minimum specification. And yes, PSI is the only parameter. You should at least get a value for each cylinder tested. You can find the spec yourself if necessary, although a reputable mechanic should provide them.

That being said, if they're all under 300 PSI "low" is all you need to know, but they should at least tell you that.

[hfschwing]

The manufacturer has a minimum specification. And yes, PSI is the only parameter. You should at least get a value for each cylinder tested. You can find the spec yourself if necessary, although a reputable mechanic should provide them.

That being said, if they're all under 300 PSI "low" is all you need to know, but they should at least tell you that.

Thanks. I was expecting to get at least a psi for each cylinder in writing. But that seems to be too much for the yard and mechanic.

[jim rosenthal]

Frankly, I think you need to find another yard, from what you say.

[Top Hatt Craig]

Do you know if the compression test was done correctly, as outlined here .. https://www.samsmarine.com/forums/sh...proceduresit’s quite a bit more work to do it correctly.

[miboatnutz]

On gas engines I do a compression check on each cylinder three times during the procedure and write down the results of each cylinder (24 values entered for each V8 engine on our Chris).

We average around 100 hours a year on that boat and have done compression checks as described three times since purchasing the boat. I take one paper copy of the results and put it in the log book and another copy goes into the engine reference manuals.

If I hired a yard to do the compression checks, I'd expect the same as a minimum for a deliverable. A piece of paper with each cylinder listed for each engine and three pressure readings per cylinder, with yard name, mechanic's name and date also on the paper.

[hfschwing]

Just an update but not sure I am making progress. Maybe a coincidence that after starting this thread I received from the yard a short summary of the compression test??

However, it raised more questions for me. The test looks to me to have been only conducted on the left bank of cylinders on the starboard engine. I would have thought that all six cylinders in each engine would have been tested? A repeat test was done on one cylinder on a separate day with a different gauge and it confirmed low compression... no info on how warmed up the engines were etc.

Yes, the pressures are low but now in the written report much lower than the verbal, I was given.

My engines smoke a little on starting when cold which was why I wanted the tests but once warmed up no problems.

Total hours are 2850 with a complete rebuild done at 2000 hours (by Detroit).

Block heaters are installed by they flip the breakers when used.

I think that I am basically SOL on having any faith in the recent compression test. Certainly too many questions to kick off a rebuild! Given performance is "ok" I will limp along for a while and use the boat(recently bought it and have not done much with it yet)and re-conduct the compression tests when symptoms go south but will be explicit about what I expect and also be present for the tests.

Thanks for all the input.

[Top Hatt Craig]

As a former auto mechanic the procedure and observations in this excellent write up make perfect sense and I would regard them every bit as important as a compression test ON A TWO STROKE DETROIT. .. https://www.samsmarine.com/forums/sh...-DD-by-Genesis