Oil pressure issue. Help please!

Okay. Here's the issue.

2004 SAN 330 Excalibur 5.7

Taking boat out of winter storage today. Fired her up on dry land (water hose connected) to warm up the oil for an oil change. When the boat started up I noticed the oil pressure gauge being a bit erratic. It stabilized after a few seconds so I chocked it up to first time the boat had run since the fall. Content all was well, I stepped away from the gauges to clean and get other stuff ready letting the engine run. Came back to the gauges and oil pressure had dropped to zero and had 'low oil pressure' message flashing. Crap!!! Shut off engine. I suspected it wasn't an actual pressure issue as there was plenty of oil and the engine hadn't exploded. Hooked up a mechanical pressure gauge and was reassured...oil pressure is perfectly normal...thank goodness. I do not believe the gauge is the issue as I got zero on the gauge AND the flashing message.

So-I replaced the sender. Had to order the pressure switch-it arrives tomorrow. Overkill? Maybe. Don't care.

I cleaned the terminal ends of the wires connected to each. Tomorrow I'll replace the pressure switch and reattach the wires.

My question is this...let's assume replacing both the sender and the switch and cleaning the ends of the wires that attach to both do nothing. Where do I go from here? I noticed the switch side of the tee has two wires and the sender side has one. Anything to look at there? Bad ground?

Thanks in advance.

Thanks for the response.

I tried with the new sender installed. Same issue. Tomorrow I'll try with the new pressure switch. Seems like it wouldn't be the gauge only because I'm still getting the "low oil pressure' message. I mean, if it was the gauge, I'd think I wouldn't get the message as that comes from the switch, not the sender-or am I wrong? I could be completely wrong!

If it is this box, this is something I've never heard of. What is it?

Thanks again!

Ok. I researched the box. Nightmare scenario!

I didn't notice if the gauge cycled on start up or not. I'll check that today. I'm praying that since all the other gauges work it's not the box.   If it is...ugh.

Thanks again.

The plot thickens.

Sender and switch both replaced. When I fire up the dash, the oil pressure gauge barely twitches (maybe a millimeter) but the volts/fuel cycle to zero then rise back up to their normal values. There's plenty of sound and whirring noises behind the dash as usual.

Start the boat up. No oil pressure on gauge and the low oil pressure message still flashes. BUT the check engine light is not on.

With all the other gauges working, I'm thinking bad gauge.

Now I gotta figure out how to pull the sucker out and bench test it.

Lenzilla wrote: I'm one lucky guy. bad connection behind the dash. Thanks for the help!!!!!!!!

   Glad you are all set! I've had dash gremlins this spring, too.

PS. If you need a PerfectPass replacement gauge, I can hook you up. I had to do that this year.....