'99 Optimax 150 DFI - Troubleshooting Constant Alarm

[tyrenta]

Hi all -- Constant alarm just started on my 1999 Optimax 150 DFI, as soon as the engine turns over the alarm starts, still getting the alarm when the engine is cold. Reading the owners & service manual it looks like either a no oil flow or overheat alarm. Here's where I'm at:

- I recently refilled the external oil tank, and I'm getting good flow to the onboard engine tank, when I unscrew the bleed cap, oil flows out of the tank
- as far as I can understand, there is no separate oil pressure or flow sensor, seems to be built into the pump itself
- the alarm begins as soon as starting cold, so if its an overheat alarm I assume that would be a bad sensor
- I have not checked the oil pump fuse yet, but at one point this weekend I did start the engine and did not get an alarm, so I'm assuming its not the fuse (I had also checked all fuses a few weeks ago and all were good)
- I need to go back and look harder if any wires are unplugged, but I don't believe so (the engine cover does have a knack for disconnecting things when putting it back on) -- I did disconnect the filter water sensor and oil level sensor thinking it was a water/low oil alarm, but then I realized it was constant beeps and the alarm for those are 4 intermittent beeps
- The only other item I can add to the list as a possible cause is a possible ECM issue, not sure how to test this

I dont have immediate access to an ECM reader, are there any steps I can take to further diagnose the cause, or am I missing anything above? I had a late start this season, had water in the tank, switched to an external tank, ran it once with no issues and the next time out the alarm began. I am also getting strange high RPM readings on the console (ie 3000 rpm at idle), which I attributed to dirty harness contacts at the helm, but I haven't had a chance to clean them yet to test.

EDIT: If it is the oil pump, the service manual notes to use the Mercury scan tool to prime the new pump; Is there any other way to do this if I don't have access to the tool, or am I stuck taking it to a dealer?

 

[R_P]

First off break out the external tank again and do premix until you can pinpoint the reason
Not sure on that particular motor but key on engine off, moving from neutral to full forward 5 times in ?10? seconds can activate an extra oil program.
Try disconnecting the temp sensor but it does seem oil related though. When was the last time you changed the inline oil filters?

 

[tyrenta]

Thank you very good point on the premix I should have thought of that, I'll do that and try and dump as much non-premix from the system as possible before starting again; Inline filters afaik have not been done, at least I haven't in the 4 years I've owned it. I'll try to locate where they are but if anyone could point me to where they are located I'd appreciate it (I assume they are on engine after the engine reservoir?); the parts manual has no filter listed on the oil injection page or air compressor page that has the oil pump

EDIT: I don't think there is an inline oil filter on this engine, best I can tell

 

[R_P]

Not sure of your engine but there were in line oil filters on some (most) optis.

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