Oil consumption

northern

Well-Known Member
Jan 17, 2007
3,516
Anacortes Washington
Boat Info
380 Aft Cabin 1989 Charts Timezero radar Furuno
Engines
Twin 454 strait shaft
Not a SeaRay engine
Have a 2008, 350 Vortex with 180 hours on it in my jetboat. Run it at 3,700 RPM most of the time. Use SAE 30 single weight oil. Manufacture recommends 30 or 40 weight oil.
This summer engine started to use a quart of oil every 10 hours. We ran it 8 to 13 hours a day for two weeks.
Raw water temperature 65F all summer.
Engine is closed cooling system and runs at just under 200F at 3,700 to 4,000 and 160 at 1,400 RPM.
Did dry compression test (Engine had sat for 3 months) all cylinders 150 +/- 5 PSI except two that were 178 and 180.
Did wet compression and pressure up on average 30 PSI.
Spark plugs brown, electrodes not burn. One person comment was looks like engine is running rich. Black deposits on threads near electrodes.
Engine does not use oil at 1,400RPM
No visible sign of engine burning oil on start up or when running, PVC valve not plugged, no oil in PVC hose, no oil in bilge, no oil on exterior of engine.
Questions
Should I go to SAE 40 or other type of oil
Any other test I can do
Is this oil consumption normal when running engine for long time at high RPM.
 
Thanks, Golfman good point
I had one leak on a 454 and it sucked water into the engine when it shut down. I am not losing or gaining coolant on the 350.
 
I'd use a multi-visc synthetic for oil. My guess is most likely you failed some valve stem seals. Easy fix.
 
What pump do you have behind it? Continuous 3700 is a pretty high duty cycle. I would try the 40.
I had a 5.7 Kodiak in front of a Hamilton. It didn't like the straight 30. Went to 15/40 and it was then good to about 60 hours before the oil started to drop.
 
What pump do you have behind it? Continuous 3700 is a pretty high duty cycle. I would try the 40.
I had a 5.7 Kodiak in front of a Hamilton. It didn't like the straight 30. Went to 15/40 and it was then good to about 60 hours before the oil started to drop.
Thanks
American jet 309
Will try 40 weight
 
I’ve been waiting to use this…

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You go first. How can you tell a new boater? Follows pirate lady’s joke advice.

Caution must be used when posting stuff like that.

Problem is, no offense to anyone on the site, but there are some folks out in the wild, with less than zero mechanical aptitude and even less common sense, that will try anything they see on the internet. If it's on the internet, it MUST be TRUE.
 
One person I worked with said if you assume your workers know 10% of what you do you will never be disappointed.
 

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