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Twin 318s lose oil pressure

M

mattv

Contributing Member
Back again guys...

I had very little time home this summer so I only took the boat out a handful of times... The last trip was to Catalina Island and she ran great until I arrived there. As I came off plane and down to idle at the harbor entrance the oil pressure alarm goes off on the starboard motor and then on the port... Both gauges read just above zero!!! Suddenly port motor dies... I hand the wheel over to the wife and head downstairs, starboard is knocking like crazy. No oil in the bilge and plenty on both dipsticks. I left the starboard running and tried to start the port with no luck so I limp in to the harbor. 20 minutes later while waiting for the mooring I get the port to start but I will not run under 1000 rpm... Made it to the mooring on the starboard and called it a day. Next day both engines fired up with 60psi and starboard did not knock at idle with in neutral but did if you gassed it or put her in gear. Ran back home on both motors at a 8 knots port ran great but starboard knocked terribly the entire time and kept loosing oil pressure until it settled out around 5 psi. Definitely not valve train noise so I'm sure it spun a bearing, so picked up a long block. I had taken the boat out the day before the island trip and ran about 20 miles without issue then fueled her up. The only thing different between those two trips and the rest of the summer is I ran with rotella 15w40 rather than 30w. The temp gauges both read fine at the time but I had loaned my temp gun out so I could not confirm that. Any ideas what could cause both motors to lose oil pressure at almost the same time? They have totally separate electrical systems and the only circuit showing trouble was oil pressure so I do not think it was a spun bearing and an electrical issue at the same time. The only thing I can think of us heat and the multi viscosity oil, any input would be appreciated and sorry for the long post.

Thanks,

Matt
 
Had it not been for the "knocking like crazy" and this engine dying....., I'd have suggested a possible faulty oil pressure gauge or sender unit.

Loss of oil pressure (in particular down to just above zero) and this knocking is not a good sign.
The fact that you went ahead and purchased a new long block, tells me that you're thinking along the same lines.

Is this a planing hull?
At what hull attitude were you operating at?
At what RPM range?

I ask because if you were running between hull speed and planing attitude, you'd have been running within an RPM range that demands more from your engines.




.
 
Rick,

It is a planning hull and I was running between 3,000 and 3,300 rpm. According to the GPS she was pushing 17 to 19 knots which varied with the sea conditions. Hoping there was not any damage done to the port motor... Which is the motor that died, but ran totally normal the whole way home. The knocker never quit running.
 
Have you changed the oil filters recently, or go to a different brand? I went from NAPA to Bosch this season since I got a free pair of Bosch. I've noticed funny oil pressure fluctuations all season. Nothing dangerously low as your describing but still noticeable, especially after running under load.

Check your filters.

Thanks,
JJ
 
Will I have always used fram filters, has anyone had trouble with that brand? Kimcrwbr1 each engine has its own intake for raw water.
 
I use them exclusively.......... In my FORD's ;)

Seriously I would use them over the Fram regardless. I never thought about them
working on a Chrysler but now that I know I will. They have the drain back valve
and are equal to or are the same as the Purolator Pure One filter.

BTW, i think I mentioned this before. I had a Bosch platinum spark plug break off up inside
the plug. Half the ceramic just broke off in the cylinder. My mechanic told me it 'happens all
the time'. I got lucky and the engine jumped a couple 'links' on the timing belt but didn't
bend any valves but I don't bother with anything Bosch anymore.
 
It sounds like you flat ran out of oil in both engines. When you came off of plane a very low oil level might slide forward and starve the pumps. If the missing oil is not in the bilge then it either never got in the engines when they were changed, or for some reason the Rotella does not drain down into the sump as well as the 30 weight (Can't imagine why). I realize both these seem unlikely to you (and I can't explain the dipstick readings you thought you saw) but the alternative explanations that involve simultaneous failures seem even more unlikely. And the fact that one engine lunched means that the low pressure oil readings were real.
 
Been using 15w 40 Rotella for years & beat my engines like a rented mule, I've never had a problem, the best oil on the market.
 
Thanks for all the input guys' I really appreciate it. Cabo John I pulled the engine on Friday and I am getting the long block ready, bad engine had 8 qts of oil so I'm not sure what to say on that. What fram filter have you guys used for the 318, ph43 or ph8?

Matt
 
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