496 HO Mystery Horn, not logged in ECU

[Bootkie2]

I've been battling a mysterious smartcraft horn on my 06 Formula 260 496 HO. The solid single beep will go off sporadically (maybe once every trip or so) and always at various rpm ranges. No rhyme or reason. The engine will hiccup for a second then return back to normal operation. (It's the same beep that happens when you start the boat).

Fuel pressure , oil pressure, manifold & water temps and pressure, +voltage is all normal.

There are no active faults/history in the ECM and I did a major tune up this year too. I put in a new IAC(+muffler), sea Pump( housing AND impellar). plugs, coils and wires.

I think I have made some progress though. Discovered recently that the main electrical harness is not OEM. The connecting pins are in terrible shape. They are all a greenish blue color (definitely some corrosion it seems) and they are all different lengths too which makes me wonder if some were tugged/bent or fried at some point.

I cleaned them and reseated the harness and the last few times we took the boat out, I tugged and seated the harness the best I could before departure.I have not gotten a horn since.

Wondering if that's enough and should I just bite the bullet and get an new OEM harness? Or should I hire a Marine electrician to dig deeper before I start making assumptions? Or is this something I can test DIY with a multimeter?

This is a tricky one because the horn is not logging anything in the ECM and the engine vitals are normal. I don't want to just helplessly start throwing more parts at it hoping it will fix things.

What should in do? Anyone have any good advice?

 

[alldodge]

When the alarm goes off is there any noticeable power reduction?

What is about the lowest rpm level that the beep went off, somewhere above 2500 rpm

 

[Bootkie2]

It's all over the map. It's happened at cruise speed. It's happened at 800 rpm. Definitely feels like a slight power reduction after the horn before it returns back to normal.

 

[alldodge]

Could use the engine serial number, but being an 06 it may have an in gear switch. If it does, disconnect the switch and see if it does it again. You will not have the interrupter switch

 

[Bootkie2]

Ahh silly me forgot serial.its OW618544

 

[alldodge]

Ahh silly me forgot serial.its OW618544

Thanks, you have an in gear switch

 

[Bootkie2]

Thanks for the advice, I'll have to do some more digging here and get back to you!

 

[Bootkie2]

I tried the gear switch and I've also been seating the main harness in tight every time we head out. Have not gotten any smart craft horns in the last 3 trips out where as before it was sounding at least once per trip. Hard to know if its the harness or the gear switch. I don't know how to test further? I guess just replace both and hope for the best?

 

[alldodge]

If your lube oil is low, or if the lube bottle is bad and telling the ECM its low, there will be a constant horn and power reduction.