Hi folks, hoping you can guide me in the right direction. I’m heading down the ICW and am now in Jensen Beach, Florida. I’m on a new to me 1985 Ultra with the above engine, and little experience with it. I’m not getting any oil pressure alarm, but my gauge starts off reading 50 psi and about 45 minutes later drops down to 38 and eventually down to 25psi. It also seems to be engine rpm dependent, i.e. lower psi with lower rpm.
Is there a way to troubleshoot if it is the oil pressure pump, sending unit, gauge, or something else, or should I start with replacing the pump and go from there?
Also, I don’t have any alarm lights that come on with the ignition on my control panel. Is there a pressure alarm, and is there a way to tell if that’s working?
Thanks so much for any responses.
Steve Mueller
Southpaw
1985 Nonsuch 30 Ultra #300
Wareham, MA
It sounds very similar to the way my old Universal 35 produced oil pressure.
As oil warms up it gets thinner and flows trough the somewhat worn bearing clearances easier so that at a lower RPM the oil pressure is lower than at a higher RPM.
I think that there are two items warming the oil. First, the engine combustion heat warms the oil. This accounts for the first stage of the pressure drop. The second oil warming issue is the temperature of the engine compartment. The temperature in this space rises more slowly than the the engine itself and accounts for the second, lower oil pressure that you report.
If you had a nice new engine with less worn bearing oil clearances, the oil pressure gauge would probably not change at all with rising normal engine temperature. The reason for this is there are two items in the engine responsible for moving the oil through the engine. The first is the oil pump. In a new unworn engine, the oil pump can move more oil and hence pressure than is desirable at all oil temperatures. The second item, to prevent excessive oil pressure, a spring loaded bypass valve, at the oil pump outlet, opens and dumps excess oil back to the oil sump. As the oil warms, since the oil flows easier through the bearing oil clearances, the bypass valve closes some maintaining a relatively constant oil pressure. At full oil temperature in a new engine, the pump likely can move plenty of oil in relation to the engine wear condition so that at cruise RPM, the oil pressure will remain fairly constant regardless of oil temperature. At idle RPM, the oil pump moves less oil than at cruise RPM so the oil bypass valve will move toward the closed position thus bypassing less oil to the sump.
There is a rule of thumb indicating that you need at least 10 PSI of oil pressure per one thousand RPM to be out of trouble. It appears that you meet that standard.
What does Westerbeke or Mitsubishi indicate for minimum acceptable oil pressure?
I doubt there is anything “wrong” other that wear on a 40+ year old engine. This engine may have many more operating hours of life.
All that said, when was the oil last changed? Did you use the correct type and viscosity oil.
Steve: You pressure doesn’t seem too bad. You should have about 10 lbs at idle speed of 850 – 900 rpms At 2500, I believe my W-27 has around 60. As someone said, we’re assuming you have clean oil. If you are not comfortable, have someone check your pressure with and external, calibrated gauge. I’m assume that your alarm is not coming on.
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
Ward and Joe, thanks very much for your replies. I believe I used the correct oil; it was Rotella T5 10-30. I just changed the oil; it has about 20 hours on it.
The alarm is not sounding, but is there a way to test that it is working?
Thanks again,
Steve
Southpaw
1985 Nonsuch 30 Ultra, #300
Wareham, MA
I am glad you have a new to you Nonsuch and that you can get out sailing these days.
We also have had problems with our oil pressure alarm. There is a wire that comes off the top of the sender/switch on the top of the engine. I am going from memory as it is a long time since I have been on the boat, but it should be shown on your manual. I recall it being near the front of the engine (toward the stern) on the port side. In our case the wire was loose and oily. Once cleaned up and the contact was made firm it functioned properly. The alarm on our boat is an audible squealer which is located on the starboard side of the companionway. The alarm sounds when the ignition is turned on and prior to the rise of oil pressure and then again when the engine is shutdown prior to turning off the key.
Peter Moodie
Nonsuch 30U Catalyst #366
Sidney, BC/ Winnipeg, MB
I don’t know the specific numbers for this engine, but it sounds like normal behavior. Oil is thicker and pressures will be higher when cold, it thins and pressures drop when warm. Pressure also varies with engine speed because the engine drives the pump. So the faster it turns, the harder it pumps and the more pressure you get. If the engine is not working hard, it doesn’t need a huge amount of pressure. (Many small engines don’t even have pumps, they just rely on splashing.)
Do you drive a Ford pickup by any chance? I’ve read that Ford oil pressure gauges are really more like mechanical idiot lights. As long as there is adequate pressure, the needle just sits the middle. Nothing wrong with that, as long as there is adequate pressure, you don’t really need to know exactly how much there is, anyway. I don’t know if that is actually true about their gauges, but it’s pretty common to see people move from Ford to Toyota and suddenly notice the same symptoms that you have. (My Tundra does this, too. Apparently Toyota gauges measure actual pressure.)
Rotella T is a great oil, but 50 hours is all you will get in a marine application, 80 - 90 with T6 the synthetic. Oil pressure you see is normal. The alarm lead can easily be displaced so check it is attached to the engine.
There should be an alarm sounding before you start the engine, with the key turned on. If not, you may have a faulty connection or alarm buzzer. It should go off once the engine is started.
On my NS30 it is on the starboard side of the companionway next to the ladder.
Bob Gehrman
NS30U #396 “Quickbeam”
Baltimore, Maryland
Steve: Bob is correct about the warning buzzer. Turn your key on without cranking and it should be quite audible. It should also be heard above the engine noise when running. I’ve had to replace mine this year. I strongly suggest that if it’s not working, you immediately get it repaired. Check the wire at the sender first. If it’s still connected, disconnect and short to ground. If no buzzer, apply 12 VDC directly to the buzzer. If no buzz, replace it from the local auto parts store. Short story – once several years ago while delivering a 34 ft something, and going through The Great Dismal Swamp, I heard a strange noise, noticed the lack of oil pressure and immediately shut the engine down. Too late. Cost the owner about 15K for a rebuild. That boat did not have a warning system installed!! As a retired mechanic, I can’t over emphasize the need for a working alarm system!! BTW, it is also triggered by overheating.
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
Hi Steve,
I am not the go to mechanical guy, far from it. However my mechanic who has been around the Westerbeke diesels for some time said NOT to use Rotella T5 synthetic but use conventional T4 and for us in Atlantic to use 15W40 grade.
David Godfrey
NS30C #145 Thursday’s Child
RNSYS Halifax Nova Scotia
I have been using the T6 synthetic for about 5 years. When I had my oil analyzed before and after, using the T6 was better.
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
OK, excellent information from all of you! This is indeed the best forum I have ever belonged to!
Yes, my alarm buzzer works before and after running the engine…I didn’t realize however that it was actually measuring oil pressure, so I’ve learned some very important things today. I will use T6 for my next oil change as well.
Thanks again,
Steve
Southpaw
1985 Nonsuch 30 Ultra, #300
Wareham, MA
When we bought our 30U in 2002 the alarm would buzz when we idled the engine. The mechanics changed the oil and said we had too much. I did not understand why too much would cause an alarm, but I was new to diesel engines and accepted that explanation. A few weeks later the alarm was buzzing again - too much oil. If memory serves, we had an injector leaking fuel into the oil, which was thinning the oil and causing the pressure to drop at low RPMs. i presume you are checking your fluid levels - if it is rising, you may have the same problem.
I think your mechanic who changed the oil should have smelled it and investigated why it was too full, Lloyd.
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
Will not argue with you on that, Joe. The yard manager did not properly instruct a new, young mechanic. I don’t use them anymore, although the yard is now under new management..
Steve,
My Westerbeke 27 Operator’s Manual says that for normal operation, oil pressure will range between 50 and 70 psi. Attached is a photo of my engine controls panel with the engine in normal operation @ 1500 rpm. The oil pressure gauge reads 75. Not sure what all that means for a 37 year old engine (and gauges) with ~2600 hours but some more data for you to consider.
Best,
George Berntsen
Wave Dancer, 30U #283
Black Rock Harbor, CT
We have a very similar engine, a Westerbeke with about 2600 hours on it, and it will read 75 at start-up and then drop to about 50 once the engine heat thins the diesel. I don’t recall seeing a reading as low as 40.
