6BTA 330 Losing Oil Pressure

[roborr24]

I recently took a job running a boat that has a pair of 6bta 330 engines. I don’t have a lot of history on the engines, other than they were “rebuilt” about 3000 hours/3 years ago, and have been running fine with no major issues since then. 

After changing the oil, I have good oil pressure at cruise and idle on both engines. After approximately 40 hours, I start to slowly lose oil pressure on the STBD engine. At approximately 60 hours, the pressure becomes so low that the pressure alarm sounds at idle, and I’m only registering around 15PSI at cruise RPM/temp. Change the oil/filter, and we are back to normal and the process repeats itself. 

Just looking for what issues could cause this so I can begin looking in that/those direction before we have a failure. 

Appreciate any and all assistance. 

Rob

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[roborr24]

Thanks for the quick response. No I have not tested it with a mechanical gauge yet. I assumed, probably incorrectly, that since the gauge was working after each oil change and lost pressure at the same number of hours, that it wasn’t the gauge. I’ll try to rustle up a gauge around here that I can use to test. 

[Tony Athens]

You seem like a hands-on guy  ??…

Have you put a quality 0-100 PSI mechanical gauge on a main oil gallery with a long enough hose on it so you can monitor it while seatrialing?

That is so  basic with an issue like you are describing.

 

 

 

 

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