temp raises and oil pressure drops on plain

[aross2566]

On my 1991 350, when on plain, my temp goes to 190+ and the oil pressure drops from around 45 psi to around 38. I changed the impellars last year. I'm getting plenty of water from the exhaust. Changed the oil and filter this year. I bought the boat last year. It's been exceptionally well maintained. I know the previous owner. He was a bit anal about the whole boat....It's been suggested the antifreeze needs changed. Any comments on this issue? Thanks for all responces.

Ancil

 

[Boater420]

Oil pressure generally tends to drop a little as the engine get's hotter. The oil thins due to the heat.

I'm not saying your temps of 190+ are normal, just that the oil pressure dropping as the engine get's hotter is normal.

Impellers should be changed yearly. After a year the fins on the impeller tend to stay bent over and don't push as much water as they used to. While not on a plane there might be enough water being pumped through the engine to cool it properly but once on plane the amount of water might be insufficient to cool properly.

Change the impeller and test it again. If you still rise above normal it might be time for risers or manifolds. You could have something else restricting the flow of water like a broken off fin or even a bad water circulating pump.

 

[CliffA]

be sure the strainers for the engines cooling water are clean....build up in the strainers can slow the flow of water to the engines....

when you are on plane the engines are working harder thus require more flow of cooling water....if the flow of cooling water is restricted the engine temp will rise.....

you can use a mechanical pressure gauge to verify the oil pressure if you are concerned...

cliff

 

[boatman37]

38 PSI is still not bad. a typical Chevy V8 only needs about 10 PSI per every 1000 RPM so at 3800 RPM 38 PSI is still adequate, but borderline. What was said about your oil pressure being related to your temps is spot on. the thinner the oil gets the lower the pressure. i used to build engines for my race cars but i'm still a boating rookie so i can't help much with the water temps other than what was already posted

 

[Jimmy Buoy]

Seems to be running a little hot, especially for closed cooling. You may be getting adequate raw water (lake water) flow, but it may be possible that the fresh water (coolant) flow is either slower than it should be or that there are some cooling tubes clogged in your heat exchanger. I'd be looking to flush/inspect all of your exchangers (transmission, oil cooler, main engine cooler) as a first step. I wouldn't suspect that old coolant would cause high temps.

If the exchangers are clear, it might be a circulation problem. That would be a bit more involved by taking off the engine's circulation pump (run off a pulley on the front of the engine - not to be confused with the raw water pump near the bottom and also run off a pulley).

Good luck!

 

[tony357]

make sure circ pump belt is not loose and or warn down.

 

[aross2566]

Ok...Thanks for all your inputs. Guess I have a little work to do.

 

[Bt Doctur]

running a 160 stat ,190 is high .could be time for new risers if there clogging up a bit