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morganbill
01-18-2009, 10:51 PM
"When I start the engine, the oil pressure is approx. 35 psi. As the temperature increases to 160 degrees F, the oil pressure drops to approx. 16 psi at 2,000 RPM. The local Volvo-Penta shop suggested going to 30 weight oil. I did, but it didn't help. I replaced the relief valve with out any change. I also used a mechanical gauge.

Would 20W/50 help? Could there be a bigger problem?

Thanks for any help."

sailmaster
01-19-2009, 07:11 AM
"Brad your oil pump may be showing signs of wear. Using thicker oil will help. Multigrade oils such as 10w 30 or 10w40 are inherently unstable. Meaning they thin out with work and shear. The technical reason can be found under my name in response to snake oils in this site. Using straight mineral oil will help, like sae 40 or sae 50. Where is your physical location? Using thicker none multigrade oil in cold climates can be a problem. In Venezuela and Columbia for example they use straight 50 weight oil due to high outside temperatures year round. I am in south Florida and I use straight 50 weight oil and have more than 20,000 hours on my Perkins 4-236. In the addition to the oil you choose, try adding "Lucus" oil stabilizer from NAPA. It stabilizes the oil viscosity and will help keep your oil pressure up. It will also protect the engine better."

morganbill
01-19-2009, 08:53 PM
"Dwight

I am in Southern California. Outside temps do not stay below 55F for too long. Not really cold. The manual recommends using 10W40 or 20W/50. I will look for a straight 40 and give the Lucas stabilizer a try. If that doesn't work, I will look at the oil pump. But if the oil pressure initially gets into the mid to upper 30's, does that mean the oil pump is ok? Can the lowering of pressure mean, 1) the oil gets thin at higher temps, 2) there may be a bearing issue.

Thanks

Brad"

rwidman
01-20-2009, 05:54 PM
"I would say that using heavier oil is treating the symptoms, not the problem. If this is an old engine, on its last legs, this may be a temporary solution. Otherwise, I would have a competent diesel mechanic diagnose and repair the problem."

morganbill
01-31-2009, 11:52 PM
"One other sympton I noticed. There is a black streak coming from the exhaust discharge port that runs down the boat to the water line. I haven't noticed any significant burning of oil, so could this be from the fuel or is it an indication of oil blowing past a gasket and getting into the exhaust?

Brad"

vics
02-01-2009, 05:17 AM
"If its not using a significant quantity of lubricating oil then its not lub oil being burnt. Tends to produce a blue smoke anyway.

Black sooty exhaust is pretty normal with a diesel engine. If there is a problem with combustion eg due to poor injectors, you'll get black smoke esp under heavy load.

If no oil being burnt and no excessive black smoke stick a bit of plastic pipe in the exhaust outlet so that the water does not run down the hull."