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high oil pressure

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dpcub

Contributing Member
I have used the outboard forum in the past, and you guys are great and very helpful. I have a problem with my other boat and need your help. I am an aircraft technician and inspector, so I have an understanding of mechanical things, but am not experienced on boat engines.

I have a 32 Baja Outlaw with 454 Mag MPI's. several years ago, I had the starboard engine replaced with a new crate engine. It now has around 100 hours. when the engine was installed the oil pressure ran about 10-15 psi higher than the port engine, which didn't concern me. The engine has factory remote filters mounted above the port rocker covers with a plate at the old oil filter location and lines running up to the filter. I am using Wix 51069R racing filters and Valvoline 20W50 racing oil.

This summer, on one trip, the oil pressure on the starboard engine went up about another 10-15 psi. when the oil is cold at cruise rpm (about 3000-3500 rpm) the pressure runs about 70-80 psi. the gage only reads to 80. The port engine runs around 50-60 psi. When warm at idle the port engine runs about 30 and the starboard is around 50. I also developed a small oil leak on this same trip.

I found the sender on the starboard engine a little wet, so thinking that was the complete problem, I replaced it with a new mercruiser sender. The pressure remained high and that sender is now a little wet. I disconnected the sender wires at the gages and jumpered to switch the gages. The high oil pressure followed the starboard engine to the port gage and the starboard gage read lower when connected to the port engine.

I was told the remote filter installation has a bypass to protect the engine if the filter gets restricted, so I installed a new oil filter, but that didn't change a thing. I can't understand how that could affect the oil pressure anyway. The engine doesn't have much time on it. could the main relief bypass be sticking, which means pulling the engine to get the oil pump out.

Please help and thanks for your help.

Dan
 
Most (but not all) oil filters are "one way" and if the lines to the filter are "bass ackwards" you will have a problem. I learned that the hard way many years ago on the engine oil feed to a Paxton supercharger on a car I once owned.
 
dpcub said:
I have used the outboard forum in the past, and you guys are great and very helpful. I have a problem with my other boat and need your help. I am an aircraft technician and inspector, so I have an understanding of mechanical things, but am not experienced on boat engines.

I have a 32 Baja Outlaw with 454 Mag MPI's. several years ago, I had the starboard engine replaced with a new crate engine. It now has around 100 hours. when the engine was installed the oil pressure ran about 10-15 psi higher than the port engine, which didn't concern me. The engine has factory remote filters mounted above the port rocker covers with a plate at the old oil filter location and lines running up to the filter. I am using Wix 51069R racing filters and Valvoline 20W50 racing oil.

This summer, on one trip, the oil pressure on the starboard engine went up about another 10-15 psi. when the oil is cold at cruise rpm (about 3000-3500 rpm) the pressure runs about 70-80 psi. the gage only reads to 80. The port engine runs around 50-60 psi. When warm at idle the port engine runs about 30 and the starboard is around 50. I also developed a small oil leak on this same trip.

I found the sender on the starboard engine a little wet, so thinking that was the complete problem, I replaced it with a new mercruiser sender. The pressure remained high and that sender is now a little wet. I disconnected the sender wires at the gages and jumpered to switch the gages. The high oil pressure followed the starboard engine to the port gage and the starboard gage read lower when connected to the port engine.

I was told the remote filter installation has a bypass to protect the engine if the filter gets restricted, so I installed a new oil filter, but that didn't change a thing. I can't understand how that could affect the oil pressure anyway. The engine doesn't have much time on it. could the main relief bypass be sticking, which means pulling the engine to get the oil pump out.

Please help and thanks for your help.

Dan
Click to expand...

I don't have your engine but with 20-50wt oil My engine is 50 psi at idle and 65-70psi at 3500RPM.

with the 30wt oil I used in the past I had 10-15psi lower pressures. I did change the filter to purolator plus so that also is a possibility.
 
someone use the wrong spring in the oil pump. Or wrong oil pump, threw in a hv pump.

The crate motor was new? Marine motor or rebuilt by a rice car builder, and not aware of the need to leave a stock pump.
 
I'd focus on this sender being "a little wet"
sounds like inferior parts...leaking and inaccurate.

Verify pressure reading at the sender location with a mechanical (buordon tube) gauge.

Do your engines have engine oil coolers?
 
Last edited:
Oil pressure is actually governed by the pressure relief valve in the oil pump..... controlled by the pre-determined spring pressure that Chief mentioned.
Different oil viscosity can and will change the pressure some!

A filter that has caused the "by-pass" to release, should have little effect (if any) on oil pressure! It would simply take a portion (or all) of the filter media out of the loop!

I agree with hystat..... Verify pressure reading at the sender location with a mechanical (buordon tube) gauge.

IMO, it would be a real shame if you had to pull the engine, but excessive oil pressure is neither good, nor necessary!
 
thanks for all the help. The oil pressure was fine for several years with this installation. The filter lines and pump have not been changed. I have run this oil and filter since the engine was put in. everything was fine until this year. I had an increase of 10-20 psi while boating down lake michigan in august. it happened almost immediately. I have not checked with a gage at the sender port, but I will. thanks. If it turns out with a good direct gage to be high oil pressure, what should be my next move? thanks again for your help.
 
one other thing. I believe I do have oil coolers. mounted below the rear of the engine? a long cylinder with water hoses attached.
 
I don't want you guys thinking I am ignoring you, so here is my plan. I will be leaving this morning for the weekend. I am going to the river where the boat is located. I have put together a test gage set up and will check it this weekend. I will get back on here monday morning with the results.

Thanks for all the advice.
 
ok.... I have checked the engine with 2 different test gages hooked directly to the engine. They match the gage in the boat, so the problem is in the engine. When cold I get a pressure of 60 psi at 1200-1500 rpm, increasing to 75-80 at cruise rpm of 3000-4000. when the engine and oil is warm the idle pressure is still 40-50 psi. what should I do?
 
oil galley, bearing, or pump is clogged up maybe.

Want to give it a run thru with one quart of kero and the rest oil. Drain a quart of oil off and add a quart of kero run it for a half hour drain, change filter and see what the pressure is.

Or pull the motor drain the oil and turn it over and go in and see whats what.
 
Had same problem with my truck and it turned out to be a partially collapsed element in the spin on oil filter.
 
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