High Oil Pressure and High Temp

[focker1636]

Mercruiser 5.7L 250 with Alpha One GII with 125 hours. After running fine all day the oil pressure started spiking today, which has never happened previously. Ran the boat in the lake with the engine lid open and the was no evidence of oil leaking or smoke. Oil pressure went back down to normal, @40 after a minute or so of idle. Turned off the engine for a while in a cove and then started heading back to the ramp. By the time we reached the ramp the engine temp rose to @200, oil pressure rose to @65, and there was some smell coming from engine. Cut the engine and trailered the boat.

Where should I start to look? Oil change and summer service was performed in May, or @15 hours of run time.

 

[focker1636]

Re: High Oil Pressure and High Temp

I ran the engine for 20 minutes last night in the driveway with muffs and am now really scratching my head. Talked to a long time boat mechanic who assured me the oil pump is either not working or working fine. He said that he's never had one go intermittent and if it did stop working for even a short period I'd know it.

After running at idle, at 2000 RPM for @5 minutes, and at 4000 RPM for @5 minutes I can't replicate the problem. Engine is purring. Obviously, if the oil pump was bad the engine simply wouldn't be getting oil and I'd hear knocking and shortly seize. If the water pump or impeller was bad I'd be overheating pretty quickly. Impeller is 2 months old. Nothing.

Oil pressure is staying @45 at idle and will climb to @60 at 4000 RPM. I tried desperately to spin off the oil pressure sender to hook up a mechanical guage, but could not get it to budge for the life of me. After 30 minutes of trying and nearly a half can of WD40 later no budge. So, I did hook a multi-meter to the sender and the Ohm range is right where merc says it should be.

My temp gauge is definitely acting up. The needle would stay around 175, then drop down to 120 quickly, then jump up to 150, then back down etc... I placed a temp reader on the one of the water hoses on the engine, thermostat, and in the water coming from the exhaust area and am getting consistent readings of @145 degrees.

So, are gauges my problem? Should I replace the gauges themselves or is there another component in the mix I should check?