Loss of oil pressure

[Fxportapot]

I have a 2000 seaswirl 4.3gl w/ penta sx. We were on the lake this evening (be jealous 82 degrees and sunny here in NC). I pulled the boat up to about 4k RPM and it started making some knocking, oil pressure was at about 40psi, backed it down to around 3k and all was well. Gradually the oil pressure kept dropping so we called it a day. Pulling into the ramp oil pressure was 10 or less at idle and the engine was making some noise, like it wasn't gettkng oil. Once home the oil level is perfect. Oil pump? Clogged something or other?

I had something similar happen to our 5.3 chevy and it was a bad oil filter with a malfunctioned back flow valve.

 

[Scott Danforth]

time to do some troubleshooting

first, install a good mechanical gauge and check.

then drain the oil and check. your oil could be thinned from contamination of sorts (water, fuel, etc.)

 

[Fxportapot]

Follow up:

I changed the oil. At idle it runs smooth as silk.

Bringing it up to 2k rpms it starts to knock pretty hard. Oil pressure on the gauge stayed a steady 40+, but gradually dropped to about 20 at idle.

I pulled the plugs and all look normal, with the exception of #6 was a bit blackish.

A compression test is next. I though I would also pull the valve covers and make sure everything is nice and tight, otherwise I believe it's off to the shop.

 

[RogersJetboat454]

Follow up:

I changed the oil. At idle it runs smooth as silk.

Bringing it up to 2k rpms it starts to knock pretty hard. Oil pressure on the gauge stayed a steady 40+, but gradually dropped to about 20 at idle.

I pulled the plugs and all look normal, with the exception of #6 was a bit blackish.

A compression test is next. I though I would also pull the valve covers and make sure everything is nice and tight, otherwise I believe it's off to the shop.

If you still have the old filter, I would suggest cutting it open, and inspecting the pleats for bearing material. If you find some, the engine is done.

If not, you may be hearing starving lifters. Could only guess what the loss of pressure would be at that point. Possibly a weak pressure release spring in the oil pump.

 

[Faztbullet]

Sound like main bearing spun....