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Message |
    
graham hunter
New member
Username: grahamdouglass
Post Number: 1
Registered: 04-2008
| | Posted on Saturday, May 17, 2008 - 01:38 am: | 
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I have low oil pressure, my dual station stewart warner gauges both show 20psi at 500rpm and at 2000 rpm. When I put a mechanical gauge to the engine I got around 25 to 28 psi. The engine has a new filter and new oil. I bought the boat last November and the owner said that the low oil pressure occured when he put new gauges in.
Other than that it runs quietly with very little smoke and noise |
Fred Frog
Member
Username: lilypad
Post Number: 19
Registered: 01-2008
| | Posted on Saturday, May 17, 2008 - 10:40 am: |
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Normal oil pressure for a new engine is 30 psi @ 1600, 35 @ 2000. If you are at 25-28 that isn't the end of the world. Several factors can be at play. Has the engine been usind straight 30 or 40 weight oil or multi vis 15-30? How many hours are on the engine? Are you sure the mechanical guage is accurate?
If the engine is running well I would not worry too much about the oil pressure. Change the oil regularly and you should get many more years of good service.
K |
greg lilienthal
Member
Username: glilienthal
Post Number: 18
Registered: 08-2006
| | Posted on Saturday, May 17, 2008 - 11:38 am: |
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Your engine should be using 40 weight oil. The oil pressure is too low and should run 30 to 35 when hot. There could be something wrong with your oil pump or there is excess bearing clearance. You need to monitor the oil pressure very closely because it could cause you to throw a rod through the block.
Regards,
Greg www.bomacmarine.com |
Fred Frog
Member
Username: lilypad
Post Number: 20
Registered: 01-2008
| | Posted on Saturday, May 17, 2008 - 10:51 pm: |
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Hmmmmm..... he says "Other than that it runs quietly with very little smoke and noise" I haven't seen an engine yet that "could cause you to throw a rod through the block." that ran quietly, have you? They bang and clang and make all kinds of noise when the bearing is bad enough to get ready to self destruct.
Now you can also argue what oil to use, or you can read the factory manual that says 32 to 90 degrees uses 30 weight, and over 60 degrees uses 40 weight. My boat sits in 50-54 degree water most of the time. So, as I read the book, I should not use 40 weight. But it also says that multi-grade is fine also. For -10 to +90 degrees it lists 10-30 or 10-40 as being recommended.
Since it's your boat you will make the ultimate decision. There could very well be wear in the engine, I don't see anything that you said to make me worry about throwing a rod thru the block.
K |
graham hunter
New member
Username: grahamdouglass
Post Number: 2
Registered: 04-2008
| | Posted on Sunday, May 18, 2008 - 01:16 am: |
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The motor was completely rebuilt 700 hours ago by a very good mechanic. I bought the boat last november and the previous owner said the oil presure was fine till he put new gauges in. The gauges say 20 the mechanical oil gauge I put on it says 25 to 28. Mind you I only ran it about 15 min. I am going to take it on a longer trip mid june and I will see what it goes like then. thanks for the input.
graham |
Bruce Fredrick
New member
Username: oldradiogy
Post Number: 1
Registered: 10-2008
| | Posted on Monday, October 06, 2008 - 05:39 am: |
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The interesting part is that the oil pressure is the same at 500 rpm as it is at 2000 rpm. Typically, a weak oil pump or worn bearings will result in low oil pressure at idle with somewhat improved oil pressure at the higher RPM range. I suspect, based on low and high speed oil pressure being the same, that you may have a weak spring on the oil pressure regulator/relief valve located on the oil pump. I would agree that there is little chance of throwing a rod if the engine has no knocks, but the lower oil pressure will contribute to engine wear over the long haul since the bearings will have decreased flow. If 35psi is rated, then you're looking at a 25% reduction in oil flow to the bearings with a 20 psi oil pressure. This is substantial when you consider that at the end of the oil passages, the flow may even be lower. So, throwing a rod, unlikely, shorter engine life... a good possibility. I think I'd replace the spring or the entire oil pump if it wasn't replaced during the overhaul. Springs are pretty cheap. Hope this helps.
Bruce |
Ken Johnston
New member
Username: kenandjudy
Post Number: 1
Registered: 11-2008
| | Posted on Thursday, November 20, 2008 - 05:38 pm: |
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Just wondering if you have checked your oil pressure sender. Also, if you have new gauges, I wouldn't necessarily assume the gauge is compatible with the sender. Do you know if both the gauges and the sender were replaced? Good luck! |
graham hunter
New member
Username: grahamdouglass
Post Number: 3
Registered: 04-2008
| | Posted on Friday, December 12, 2008 - 05:38 pm: |
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This thread certainly has a long life. The mechanical gauge says about 30psi, the funny thing is after a long cruise, my oil pressure needle is `pinned passed 0'the wrong way. The oil pressure alarm, which activates at 10 psi and is on a different circut never comes on. I checked with a mechanic and he said it is probably electrical and I should trouble shoot the problem with clean wire, directly from the sender to the gauge. This is on my to do list. |
graham hunter
Member
Username: grahamdouglass
Post Number: 4
Registered: 04-2008
| | Posted on Friday, December 12, 2008 - 05:40 pm: |
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I should point out the oil pressure alarm does come on when the engine is shut off and operates normally. |
Dwight Brooker
Member
Username: sailmaster
Post Number: 84
Registered: 05-2006
| | Posted on Friday, December 12, 2008 - 07:24 pm: |
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I agree with the mechanic, it sounds electrical. Get a new gauge and sending unit (not very expensive) and run a clean wire this will give you the answer. You do not even need to mount the gauge for the test.
Just for the record I was driving a truck with a 6.2 liter diesel @ -30F in Alberta Canada. The engine was running smoothly with no knocking, at a steady speed on a flat stretch of road when the rod blew through the block. There was no warning at all. It is not as far fetch as you think
Good luck |
graham hunter
Member
Username: grahamdouglass
Post Number: 5
Registered: 04-2008
| | Posted on Wednesday, April 22, 2009 - 12:32 am: |
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Just an update to my low oil pressure problems. I went out and bought dual Faria oil pressure gauges and sender unit. I now read 30 lbs pressure. I plan eventually to replace all my gauges with the Faria Chesapeake line, when I have the time. |
