Reply With QuoteWhat are you using for oil weight? It almost sounds like you are using a multi-weight. It seems to be breaking down because of heat. Synthetic??
I'm sorry if this post is off base for this message board, but I can't seem to find an answer to this problem, so I'm going to ask anyway. I am running a completely stock 1996 7.4L Volvo (carb) 310hp with 160 hours on her. You can run her all day on the primary's without a problem. Open her up over 4000rpm where the secondaries on the carb open and leave her like that for more than 5 minutes... the oil pressure starts to drop from 60lbs to 35lbs. Back off to where the secondaries close and the pressure slowly builds back up to 55 - 60lbs again. Anyone have a clue? I have checked the sending units mounting tube and it is clean as a whistle. I was considering putting an ATI Procharger on her to get some decent speed out of this rig, but I really would like to figure out this oil pressure issue first. This has been going on now for the last 15 engine hours. The engine behaves normally in every other aspect. Any help would be appreciated.
Thx,
Gene
What are you using for oil weight? It almost sounds like you are using a multi-weight. It seems to be breaking down because of heat. Synthetic??
Originally posted by moomba:
What are you using for oil weight? It almost sounds like you are using a multi-weight. It seems to be breaking down because of heat. Synthetic??
Thanks for the reply moomba, I am using Castrol GTX 20w/50. The manual recommends 20w/50 or 30wt for running in the temperature range above 32F. All of the other recommendations are for colder temps. Are you recommending that I go with the 30wt instead?
Thx,
Gene
ps. I didn't request the frown icon... And I can't seem to get rid of it (Clicking the "Disable Smiles in This Post" does not work...
[This message has been edited by AZ_Eagle (edited May 30, 2001).]
The drop in oil pressure is most likely caused by an increase in oil temp due to harder engine load. This is somewhat typical (oil gets thinner with higher temps). Unless your stuck on synthetic oil, you might want to switch to a strait 40W if the rise in temp bothers you and see if that helps. Your other alternative is to install a larger oil cooler.
.
[This message has been edited by Racing Ray (edited March 12, 2002).]
Full synthetic will help you keeping better oil pressure under load. Just make you use full synthetic oil, not blend or synthetic reinforced oil.
The tree main reasons for which you may loose your pressure are:
-Not enough oil in pan
-Some clearances are too wide inside
motor. Synthetic oil will help,
higher oil grade will also help, but
don't go higher than a straight 30
grade. Remember we talk about a
stock low hp motor.
-Oil temp. getting too high. First,
make sure the cooler is not clogged
by debris or grass, then you may
consider using a larger cooler.
You didn't mention about the water temp.. If this is a new problem, I would first have a look inside the cooler, then I would have a serious look at the water pump impeller. When you solve the problem, make sure
you mention the solution on this forum since I'm sure many boaters see the same problem with their rig.
A last point: before to add boost in your engine, make sure everything work fine.
RacingRay has a point. Try a new filter, and why don't you go for an oil change at the same time. The solution can be that simple.
I'll try the oil filter first.... you might have something there, as the pressure issue also occurred about the same time I changed the Oil and filter. I'll let you know if this solves the problem.
Gene
Originally posted by ponponracing:
RacingRay has a point. Try a new filter, and why don't you go for an oil change at the same time. The solution can be that simple.
hey ponponracing, why do say no to go higher than a 30w on marine engines??
Moomba,
30 is a nice grade of oil for two reasons: it's liquid enough to give a good internal splash when cold and it stays tick enough to maintain oil pressure when the engine is hot.
The good thing with 40 oil is that it's stays ticker when it's hot. So it's excellent with an engine with wide clearances on the crankshaft. The problem with straight 40 oil is that it is too tick when it's cold. It doesn't lubricate properly because it doesn't flow enough and since it is too tick, the oil thrown from the crank will hardly lubricate cylinders, meaning pistons scuffing.
Instead of straight 40, I recommend that you use 25-40. It's a 25 grade that act as a 40 when hot.
If you want absolutly to use a 40 grade, do as we do in racing: preheat the oil before cranking up. Interested?
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