FYI: 2007 STX-12F engine destroyed due to bad oil pressure sensor

[cxp]

I think I figured out what killed the engine on my 2007 STX-12F.

The engine seized shortly after it was put in the water for the first time this year. Ski had about 350 to 400 hours on it at the time. We have never had any serious issues with the ski before.

I towed the ski in and found a significant amount of oil in the bilge and the dip stick showed significantly below minimum oil level. There was a lot of oil near the oil filter. I guessed that the oil filter was bad or was not sealed correctly and that oil escaped while the engine was under load.

Upon further inspection, the oil pressure sensor (located immediately above the oil filter) was missing. I found the female end of the wiring harness disconnected, and I found a small spring and a dime sized sensor fragment floating around in the hull. There was a small amount of corroded/rusted metal remaining where the sensor is connected on the engine.

The sensor appears to have corroded and snapped, allowing oil to leak out. I don't know why I did not get an oil pressure alarm.

I noticed that several other mounting nuts and bolts are extremely corroded, specifically the bolts located at the rear of the engine, above the coupler, holding the exhaust manifold. I did not see similar corrosion on my 2008 STX-15F. The skis were purchased about 9 months apart.

If you have an older 12F or 15F, and you ride in salt water, I suggest you check the oil pressure sensor for corrosion.

I'll try to get some pictures this week.

[cxp]

Just to be clear: the wiring harness still has some part of the oil pressure sensor attached, the sensor just split in half and exposed a path for oil to leak from the engine quickly.

[steve45]

My guess is that the sensor is simply a spring-loaded switch that is held open by the oil pressure. When the switch broke off, the ground path for the electrical signal was broken.

Thanks for the warning!

[sirbreaksalot]

option A: less than required engine bay maintenance has cause the corrosion, or the servicing person is blind
option B : when the oil filter was changed the sensor was lent against, ( depend what tools were used to change filter

if the sensor comes apart the ALARM must go off because the circuit becomes OPEN

Waz