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Help with Alarm

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Merc175sj

New member
Hi All!! New user, hoping for some help.

I bought a 1999 SeaRay F-16xr Jet Boat. The engine is a Mercury 175 Sport jet. My understanding is that this is the same outboard powerhead just mounted to a jet pump. Anyway the thing runs great, a little rough starting but that could be the newb at the controls :).

So the issue is that I get a sporadic alarm. I don't really have a hard and fast pattern but definitely seems to be mostly at idle or lower RPMs, but not always on when idling.

From the reading and research I've done this boat has three sensors on it - Oil level in oil reservoir, oil pump rotation, and engine heat. I tried unplugging / plugging different sensors leads on the water but it really didn't make a difference, better or worse. which as I type that seems sort of strange.

So back on land I started trouble shooting a little more controlled trying to follow page 135 of this manual

http://162.144.28.33/lib/mercury/manuals/175xr_sportjet.html#/135

First thing I checked was the oil reservoir float switch, this functioned fine and turned on/off just as quick as I put it in a out of the tank. I moved on to testing the Motion sensor and the results I'm seeing are very different then what its defining, but I'm not sure if I'm testing it right. I checked the white wire coming from the ECM and had zero volts while the key was "on", I started the motor and saw the voltage all over the place from 1 to 2 volts up to 20+ volts. When I shut the motor off it settled to 12V for a few seconds and then dropped back off to 0. So this seems all wrong to me but am I testing it wrong? Should I be testing this cranking slowly by hand? Should there be 12 volts when just the key turned on?

I'm not sure I know how to check the very first test on that page of the "incorrect voltage pulse being sent to the ECM" because I don't see green wire coming from the ECM on my motor (or for that matter any wire on the wiring diagram on page 63 of the same link). I was thinking tomorrow I might just check all of the coils voltages. Here's my question - Can I test the coil voltages while the engine is running? Do I need to pull plugs and ground plug wires before testing the coils? Does doing that actually impact any of these checks or is that really just safely driven?

Any help anyone can give me would be awesome, I think I'm getting somewhere but don't really know where to go next...

Thanks,
Doug
 
I should also mention, I don't think there is an actual mechanical issue with the oil delivery or over heating. It alarms even when the engine is not hot (cool enough to touch), there is no fluctuation in RPM you would expect if oil volumes increased or decreased for a little bit, and there's a good puff of smoke when starting and a little bit when running.
 
Its a Beep Beep Beep... Typically 4 at a time. No consistent interval between each series of 4 beeps. Yeah that's full and stays full. at one point I ran the motor on the hose with that cap off and upside down so I know the float was "up" and I still was getting the alarm.
 
Well I know 4 beep codes on some newer Mercs could mean water in fuel, so I'm not sure if you have a fuel separator with a sensor on the bottom of it but you could try that. (Make sure you have no water in your water separator.) Otherwise yeah it could be the oil gear is stripped
 
I looked and don't see anything off the fuel system like that, its a 99 so I'm not sure its quite new enough to have one on it yet or not. plus there's no running issues at all, if you turn the key off to silence the alarm you would not know there is any problem what so ever, no stalling, revving, or sputtering... not a single miss in the motor at all.

I'm still trying to track down checking the coil lead voltages, I tried to test them directly with my multimeter but I don't have a "DVA" so the readings flipping between 1200ish to "OL" doesn't really tell me much. At least they all did the same thing... I had to order a DVA, won't be in until next week sometime.
 
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