318 oil pressure fluctuation

[bcassedy]

Port engine oil pressure has been rock solid this season until the last couple of times we've taken her out. At low / mid RPM (up to say, 1900 - 2000 RPM) the pressure stays steady at about 60+ PSI. The 2nd last trip out I pushed the engines some (about 2400 - 2600 RPM and noticed the port engine's oil pressure gauge was swinging back and forth (down to maybe 30 psi and the back to normal point). If I back down on the RPM's to our normal range (about 1700 to 1900) the oil pressure returns to its normal point and stays there - no fluctuation.

I thought possibly the level was low but after shutting down the engine and waiting about 15 minutes, the dip stick reading is right at Full.

Anyone have any ideas on what to check next or possible cause? Also, with a steady oil pressure in the range I stated, would running the engine NOT be advisable. She gets pulled out of the water in 2 weeks and we have a yearly trip we've been prepping for.

Thx,
Bill

[spdracer]

Probably just a sender. I would connect a mechanical gauge and operate the boat under the same conditions. If the mechanical gauge does the same thing, then you have a problem. It doesn't sound like an engine problem the way you describe it.

[Fastjeff]

It could also be a bad connection (ground or sensed wire). That said, you definitively want to put a mechanical gage on it to be sure!

Of course, the electrical gage will behave itself when you do but...

Jeff

[barkleydave]

I had a similar issue a few years ago. Jeff is right on sensors go bad and grounds wires etc. In this case my sensor was leaking. Make a heck of a mess... Was normal at low RPMs but like yours the pressure was forcing oil out of the sensor and well a mess ... this is the second sensor I have had go bad. Quality is an issue. I now check mine often for leaks !

safe harbors,
dave

[jralbert]

jUST CHIMING IN TO ADD PERSONAL EXPERIENCE, concurring with the above. 1 - sensors leak, 2- wires loosen or corrode

[Fastjeff]

I had bad luck with the oil pressure switches--had to replace one a year for a while. Not sure why.

Note: Everyone with a Chrysler small block needs to keep an eye on that tiny tube going from the motor to the block with the oil switch and sensor. They tend to leak, and in a place where you can easily miss it. I replaced them both (twin engines) with fuel pressure gage stuff.

Jeff