hookipa wrote:
I recently moved my boat from New Zealand (cold water) to Tonga (very
warm water) and I am now experiencing very low oil pressure at
operating temperature at idle. The engine is a Volvo Penta AD31B and
I am not sure of the hours on the engine. As the engine has seperate
circuits for the oil warning light and the gauge, I believe that the
problem is not the gauge/sender. At operating speed i get about 50
psi, but at idle it sometimes turns on the warning light. Any
thoughts or checks before I pull the boat and remove the engine to
check the main bearings and oil pump?

By circuits, do you mean separate senders as well?

I recently moved my boat from New Zealand (cold water) to Tonga (very
warm water) and I am now experiencing very low oil pressure at
operating temperature at idle. The engine is a Volvo Penta AD31B and
I am not sure of the hours on the engine. As the engine has seperate
circuits for the oil warning light and the gauge, I believe that the
problem is not the gauge/sender. At operating speed i get about 50
psi, but at idle it sometimes turns on the warning light. Any
thoughts or checks before I pull the boat and remove the engine to
check the main bearings and oil pump?

On Oct 24, 9:48 am, hookipa wrote:
I recently moved my boat from New Zealand (cold water) to Tonga (very
warm water) and I am now experiencing very low oil pressure at
operating temperature at idle. ...

I doubt that the problem is the water temperature. As you know lots
of folks make that trip and don't have this problem. I'd change the
oil out for a heavier weight and see if that helps.

-- Tom.

hookipa,

A sticking oil pressure relief valve would cause these symptoms.

Dave M.

On Wed, 24 Oct 2007 12:59:25 -0700, "
wrote:

I'd change the
oil out for a heavier weight and see if that helps.

Yes, that was going to be my advice also. HD 40WT would be typical
for an older diesel engine in the tropics. You could also bump up
your idle speed a little

Hi

Check the oil pressure relief valve and clean it.

Try a heavier grade of oil, not one of the modern wide range synthetic or
semi synthetics multigrades.

30 or 40grade or possibly a 20/50 I would stick with a mineral oil for an
engine of this age.

Castrol make an oil for older higher mileage vehicles but I expect it is not
available where you are.

Alec


"David L. Martel" wrote in message
...
hookipa,

A sticking oil pressure relief valve would cause these symptoms.

Dave M.

You did not say what the pressure is at idle.

Does the guage read when idling? Some manufacturers allow a very low
pressure when hot idling. I will check my engine manual next time I go to
the boat.

50 psi when running seems quite OK.

Alec


"hookipa" wrote in message
ups.com...
I recently moved my boat from New Zealand (cold water) to Tonga (very
warm water) and I am now experiencing very low oil pressure at
operating temperature at idle. The engine is a Volvo Penta AD31B and
I am not sure of the hours on the engine. As the engine has seperate
circuits for the oil warning light and the gauge, I believe that the
problem is not the gauge/sender. At operating speed i get about 50
psi, but at idle it sometimes turns on the warning light. Any
thoughts or checks before I pull the boat and remove the engine to
check the main bearings and oil pump?

On Thu, 25 Oct 2007 11:05:13 +0100, "Alec"
wrote:

....
Try a heavier grade of oil, not one of the modern wide range synthetic or
semi synthetics multigrades.

Alec

I'm not arguing with this general advice. But the sentence I
quoted shows a mindset that may not tie to reality.

A synthetic almost as thin as water when cold, can STILL be thicker
than a thick mineral oil when really hot. Its viscosity vs
temperature slope is that much flatter. That's why they are rated
multi-grade. The synthetic doesn't burn off and has better high
pressure film strength.

Brian W

I do not know if you have the manual with you but the manual online at
volvo, states engine hot idle pressure 21 psi and full power hot 60 psi. It
does not say max or min so I assume this is typical.

Oil grade CD 15/40.

Alec


"hookipa" wrote in message
ups.com...
I recently moved my boat from New Zealand (cold water) to Tonga (very
warm water) and I am now experiencing very low oil pressure at
operating temperature at idle. The engine is a Volvo Penta AD31B and
I am not sure of the hours on the engine. As the engine has seperate
circuits for the oil warning light and the gauge, I believe that the
problem is not the gauge/sender. At operating speed i get about 50
psi, but at idle it sometimes turns on the warning light. Any
thoughts or checks before I pull the boat and remove the engine to
check the main bearings and oil pump?

On Oct 25, 8:04 am, Brian Whatcott wrote:
On Thu, 25 Oct 2007 11:05:13 +0100, "Alec"
wrote:

...

Try a heavier grade of oil, not one of the modern wide range synthetic or
semi synthetics multigrades.
Alec

I'm not arguing with this general advice. But the sentence I
quoted shows a mindset that may not tie to reality.

A synthetic almost as thin as water when cold, can STILL be thicker
than a thick mineral oil when really hot. Its viscosity vs
temperature slope is that much flatter. That's why they are rated
multi-grade. The synthetic doesn't burn off and has better high
pressure film strength.

Brian W

Stay away from switching to synthetic on an older engine, they tend to
develop oil leaks.

John