Engine temp and oil pressure high ?

[filthy_oar]

after about 20 minutes of engine run time, my port engine temp is about 175 degrees while the stbd is around 160. Then my stbd engine pressue is around 80 psi and the port is around 40. any ideas ? i hope its just the gauges acting up. engines are 4.3 mercs

 

[majoma]

My two 7.4s run at about 170 degrees so, I guess, anything between 160 and 175 degrees is normal. I am not sure about the oil pressure.

 

[skunkman]

I think your temp is OK. Most likely a bad oil pressure sender. Can you hear any tapping noise - that would indicate oil passage being impeded which would be more serious.

Good luck.

 

[BillK2632]

I don't think you have an engine problem, all of your numbers are within acceptable operating range, although the 175deg / 80psi is more normal, assuming a warm engine running above idle rpm. I would say you have a ground problem with the port engine. I would start by checking the ground connection on all of those gauges and the connections on the sending units.

 

[filthy_oar]

Ok thanks for the help. Only had the boat a month from the previous owner and he recently installed me a gauges. Engines seem to run fine with no unusual noises

 

[Seahorse]

Re: 2002 260, 5.0 Mercruiser, Bravo III - Alarm sounded as we were cruising at about 3000rpm/20mph. Slowed down went off then nothing for rest of the day. Manual says alarm sounds if there is an oil pressure, water temp or transmission temp. problem. Oil and water are fine. Wondering how you monitor transmission temp? Also manual states testing alarm by turning key on but not cranking. I tried this but no alarm. Do I have a problem?

 

[Bt Doctur]

oil 30 psi or better
temp 165 and lower
you dont have a transmission temp sender with a Bravo drive.outdrive oil res bottle going empty

 

[skibum]

I've worked on hundreds of high performance GM engines in my life, and 40-50 psi oil pressure is the "correct" range for most applications. GM oil pumps have an internal regulator designed to set the absolute pressure of the pump. See parts 6 & 7 in the diagram below.

That being said, someone may have intentionally installed a "high performance" pump with a higher absolute pressure rating, or shimmed the pressure regulator spring to increase the absolute pressure. I have only seen the springs shimmed in dragsters with 1200 HP alcohol engines that do 300+ MPH in a 1/4 mile, so that's not likely to have been done for a pleasure boat.

One time, I got a brand new pump where they did not lube the valve during assembly and it was stuck in place. Must have sat around somewhere for a while and rusted together or something. Fortunately, I always inspect an oil pump thoroughly before I install it because it sucks to have to do it twice. I was able to press the valve out, lube it, and reassemble it before I put the pump in. Who knows what random pressure that pump would have put out. Note: The pressure valve actually controls the volume of oil that the pump puts out. Pressure is created by the small clearances between the parts downstream of the pump restricting the flow. Think garden hose with your thumb over the end vs free flow. The valve acts like the hose bib on the side of your house.

Having said all of that, I agree with skunkman and think you have a bad oil pressure sender. There is a little wiper in them that is moved by a diaphragm which changes the resistance between the 2 outer posts if you have the typical 3 wire sender. I believe the normal range is 0-2 ohms for 0 psi (engine not running) and something like 88 ohms for max oil pressure (which I believe is - 80 psi).

I have 2 suggestions. You could install a mechanical gauge to verify the actual pressure. You can borrow one from an auto parts store like Autozone or Advance, etc.. But since you have 2 engines, I would simply swap the oil pressure senders between the two engines to see if the readings move between engines. That's the easier (and free) option. If that engine really has 80psi, then either the valve in the oil pump is stuck wide open, or you have a restriction somewhere downstream of the oil pressure sender.