Today my oil pressure gauge was occasionally "jumping" up and down to an extent that it triggered an audio warning (2 beeps) a few times. I have a '97 Maxum 3000 with a 496 MAG engine.
I checked the engine bay - no oil in the bilge and the oil level was fine. I restarted the engine and the pressure looked fine. While under power again the pressure dropped slightly (again, the gauge moved down in fast "jerky" motion rather than in a smooth fashion) and triggered the engine guardian system which automatically powered down the engine to idle. I shut it off and again checked the engine bay and oil. Again it was fine. The pressure looked good and stayed steady after I restarted it again.
Has anyone experience something similar? Near the end of the trip the oil pressure did read slightly lower than normal when I was motoring a slow speeds. When I throttled up slightly the gauge kept jumping up quickly before staying steady.
It was an extremely hot day and I wondered if perhaps the gauge or oil pressure sender was impacted by the heat in some way? When the readings on the gauge have moved in the past in response to powering up it was always small movements and in a smooth way, not jumping around.
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1995 Maxum 2400 SCR 5.7 A1 G2 LUNA DE MIEL SOLD
1988 Bayliner 2455 5.0 IO (sold)
1987 Seaswerl 18ft C. Cabin 4.3 IO(lost in fire)
2012 South Bay Pontoon
I believe the gauge uses a separate sensor than the alarm so this may be a real issue. Do you have the engine manual so you can confirm this? You can try changing the sensor to see if that corrects the issue to temporarily install a mechanical oil pressure gauge to verify if the pressure is truly fluxuating
Thanks very much. I think you're correct that there are separate sensors (I don't have the engine manual but I read that on another site). I agree it's worrisome since it's unlikely both sensors were malfunctioning at the same time. I'll try the suggestions and update the thread once I confirm the issue.
You could use a analogue gauge to verify the oil pressure.
There are two oil passages on top of the block you can use, one of them holds the oil pressure sender, the other one is plugged.
If the pressure on the analogue meter is OK during operation, you have some kind of electric problem, could be as simple as a corroded ground connection.
If not your in trouble...
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The older i get, the better i was.
2700 SCR, 7.4l bravo 2
I found Mercruiser manual #30 under Documents but it doesn’t have a wiring diagram in it. Either try using a manual oil pressure gauge or hook up an ohmmeter to the helm sender to see if either shows this drop.
OK I'm feeling silly but I'm not certain of the correct location of the senders on the engine. The manual doesn't have a picture and google isn't helping. Anyone have a description, diagram or photo?
One is on top of the motorblock behind the intake manifold, near the distributor.
The other one is just above the oil filter adapter.
No distributor on the 496 but the helm sender is in that same location; top rear of the engine. Alarm sensor is on port side of the block where the oil filter is or the remote adapter attaches.
Oil Pressure Warnings - Mercury 496 MAG
Linear Mode
