Intermittent oil pressure readings

[fishing gypsy]

I have a 2004 Mercruiser 350 MPI. in a Bayliner 288 Classic Cruiser. This boat is new to me. I took it out for only the second time since purchase and on startup both upper and lower station oil pressure gauges read 40 psi at about 3900 rpm. After running for 15 minutes the gauges started fluctuating from 0 psi to 40 psi. Then after another 10 minutes they both fell to 0 psi. I stopped the engine and checked the oil and it was at the full mark. Temp gauge (coolant) read 180 degrees. Oil temp gauges read 0 degrees. Restarted engine and gauges showed good oil pressure. Ran for 15 minutes again and lost oil pressure readings. I am thinking this is a problem with the oil pressure sending unit, but looking for the input on this. The engine is equipped with Smartcraft.
Thank you for any ideas.
A Wesley

 

[Scott Danforth]

first welcome aboard

second verify oil pressure with a mechanical gauge.

third, if oil pressure is good, start looking for something faulty on the electrical side.

 

[Rick Stephens]

After verifying with a mechanical gauge, start cleaning connections. Pay particular attention to grounds at the engine. Since both gauges are erratic, the problem is most likely at the other end, the motor. Stainless toothbrush time. Crawling around and inserting yourself into places not meant to be accessed is in your future.

 

[kenny nunez]

A good chance the sender has a ruptured membrane. This happened to me several years ago. The inside of the sender fills with oil and the pressure equalizes on both sides of the membrane. Be sure to specify that you have dual gauges when ordering.
Still a good idea to verify the pressure with a mechanical gauge.

 

[kenny nunez]

A good chance the sender has a ruptured membrane. This happened to me several years ago. The inside of the sender fills with oil and the pressure equalizes on both sides of the membrane. Be sure to specify that you have dual gauges when ordering.
Still a good idea to verify the pressure with a mechanical gauge.

 

[QBhoy]

Oil pressure sender sounds like the issue here. I’d also cation that if that 180 degrees reading is genuine and off the smart craft too...you are on the verge of overheating...or even on it.