Compression test

[centaursailor]

Originally Posted by brokesailor

Thanks for the input. The test results were:325, 330 and 275 I assume psig.
The good news is the Boat owner is paying for a full engine overhaul, approximately $5K including pulling the engine out, overhaul and reinstall.

Looks like a good solution, presuming the work is carried out by an authorised workshop. Are you now bought into the deal?

[LakeSuperiorGeezer]

Lets see what is found on a tear down. An automotive machinist can check for valve leaks, much like a pressure leak test only better, and check for cracks at the same time. On a marine diesel, especially raw water-cooling, got to check for cracks! He will also measure the cylinder walls for wear. There could be some real problems there on the low cylinder from a bad injector, and if the valves test good, then should pull the cylinder with the low pressure in it if obvious cylinder wear is not evident. If that engine is coming out of the boat, better have the bearings checked and journals measured. You will also new rings if you do the bearings. Since the engine is out, you should have the bearings checked, even if it were money out of your own pocket. Who knows what the maintenance was like on that engine?

[RainDog]

If the mechanic they hire is any good let me know. I sure could use a good Yanmar mechanic in the Kemah area. I am 0 for 2 so far.

[Capnblu]

If your "mechanic" didn't do a wet compression test, you have no basis to rebuild this motor. Any time you do a compression test, you should expect as you proceed to the next cylinder, after 4-5 dry compression strokes to see a declining pressures cylinder after cylinder. Also if the engine is not perfectly level, you would also not expect to have the highest cylinder as oiled as the opposite end of the engine, which will be sitting closer to the oil level that splashes, and lubricates that cylinder more. Only with the wet and dry #'s do you achieve the basis for a leak down test. A dry test only, does nothing but sell you a rebuild, or remove liability when something eventually happens. You would be better off pocketing the $5000.00 and putting it toward a proper rebuild, when you need it in the future. Also since all of the cylinders are under 15% difference in pressure, there is no basis for a rebuild, especially since there is a probability that the person preforming the test may have not seated the compression tester correctly, or possibly cranked the engine with different # of strokes per cylinder. Of course that could be weeded out with the wet test.

[svjobeth]

Originally Posted by RainDog

If the mechanic they hire is any good let me know. I sure could use a good Yanmar mechanic in the Kemah area. I am 0 for 2 so far.

The OP says the engine's a Volvo...but, a good mechanic's a good mechanic. However, factory certifications go a long way these days.

I know lots of people in the trades country wide. I'll ask around and see if I can get you a name or two.