671 oil pressure

[Calm Waters]

My starboard 671 DD is showing lower oil pressure than the port engine. At 1000 RPM and up the starboard shows 35 to40 psi while the port shows 45 to 50 psi. At 600 RPM the starboard is reading 22 psi while the port reads 28 to 30 psi. My oil pressure guages in the flybridge read the same as the guages in the lower helm. I checked oil in both engines and they are full. I also checked for leaks while running and found none. Both engines have around 1500 hrs on them. They don't smoke and run great. My boat is a 1973 model DCMY. She is in excellent shape for her age. Is the lower oil pressure in the starboard engine something I should be worried about?

 

[davidwigler]

Do you have mechanical gauges in the engine rooms? The helm gauges are notoriously inaccurate.

 

[MikeP]

What Dave said!

Pay no attention to the elec gauges until they are checked against a mech gauge. Both helm gauges for each engine use the same (single) sensor so the upper and lower gauge for each engine should show the same pressure...which could be wrong. Of course, the gauges can also be out of whack.

Check it with a mech gauge and then put some marks on the elec gauges at the proper reading for low/high pressure.

 

[Calm Waters]

Thanks for the advise. I will check to see if I have mechanical guages and if not I'll have some installed for piece of mind. Thanks again

 

[Will]

A comparison with mechanical gauge readings is the best verification of oil pressure. However, low oil pressure alarms if you have them, can help as well. If your oil pressure is really low, they will sometimes beep or go off when you idle a hot engine or shift gears. A not uncommon cause of low oil pressure on Detroits is fuel dilution resulting from problems with the fuel manifold, crossover lines or injector fittings.
Will

 

[spartonboat1]

The transducer (pressure sender) can have a bad calibration at the connection. Sometimes just rotating the wire connection at the sendor "back and forth" through 5-10 degrees will raise the pressure reading. At least on mine, the wires are "riveted" to the sender at the engine and where riveted, the connection can degrade.

My observation for these engines (6-71N, 1972).

 

[Genevatexan]

I recently reported a similar problem with my 671 Ts. Your pressures are substantially higher than mine, and I was told these engines are capable of running with very low pressures. I added mechanical oil pressure gauges in the bilge with very little effort. There was a free port on the oil junction block where the electric pressure gauge sender was mounted. I screwed in a pipe thread oil line from a local supply house and used their available gauge. I found that I was running 9 lbs of pressure on engines that have about 2500 hours on them. The warning switch should be activated at 7 lbs, I am told. In all boats, one engine is stronger than the other, but your pressures sound solid.

 

[Genevatexan]

Additional note: that 9 lbs was at 650 idle, with 39 lbs at 1700.

 

[Genevatexan]

Additional note: that 9 lbs was at 650 idle, with 39 lbs at 1700.

 

[Calm Waters]

Thanks for the info. I feel much better about the oil pressure I'm getting.