Getting a hard alarm but the computer doesn't know why
 

Hey guys,

I may just need a little more understanding of how the computer works. Earlier this summer I had a rotor screw let go that blew up my distributor system and got a hard alarm before it let go. When the code was pulled afterwards, it said Over Rev. Got it all fixed up and running great, but at WOT for a couple minutes I'd get another hard alarm. I check all the hard alarm items and everything is in spec. Boat running great. Eventually that alarm just goes away under the same conditions. Boat has been running great. This weekend I was at the Texas Boat Forums fall run and I had sucked up some seaweed in my out drive raw water pickups. The starboard engine had started to get too hot and the alarm went off. Shut it down right away, found the problem. Ran the Rinda on it, it said "Guardian mode unspecified" or something similar. Started up again, engine immediately went to perfect temp. Got going again, ran about 5 minutes at 3k RPM. Then hard alarm. Shut it down, again scanner finds nothing on either engine. I start it up again, cruise nice and easy, then go in higher RPMs and no alarms.

My question is: Do these codes tend to linger around and trigger alarms until they have a chance to clear out on their own?

Thanks!

Need more info.what processor is on the motor..mefi or pcm-ecm.depending on what you have the code will clear when the problem that created the code has been repaired.also the processor needs a certain amount of consecutive counts in order to log a code.

I have Merc 6.2Ls. Not sure what the computer specs are.

I have Merc 6.2Ls. Not sure what the computer specs are.

You did not post year and do have a Catalyst 6.2 's. Two different ECM 's for these 2 different engine set ups FYI

NON CAT is ECM 555 Motorola

Catalyst 6.2 PCM 09 Visteon

next no such this a old codes lingering if they been been fixed properly 100% as far as the engine / guardian mode and warning horns still active..

You have a hard alarm describe it exactly. ______ or _ _ _ _ or _ _ . _ _. _ _ . _ _ or ???? depending on what your have. Very hard to throw out answers not knowing what you have exactly.

Example my starter does not work do have one Any place selling starters reply - What in the world do have for app so we can see if we have the correct starter for you. More info is needed THX not dogging you just needing info .

Are you able to reach WOT at the correct RPMs, how well does your engine start up and run at idle and during throttle up ?

Totally OEM marine certification, so I know what whats about this completely. Masters, to lazy to take the written test and its would just hang on the wall of shame anyways.

I almost came down to your run to hitch a ride. But I am still stuck up here.

Would have been great to have you down! It was fun. They are 05 non cat models.

Desribe your alarm going off and on your scan does it say available power 100% or what does it say % wise for available power ?

You have ECM 555 Motorola computers on your mercruisers FYI

I'll take a stab at it without your info to help. You have a possible of 4 problems that one or 2 is your problem. At full throttle the alarm can be a true overspeed alarm meaning you are bumping off the rev limiter - not good to do. Next the WOT alarm could be low block water pressure meaning either slight restriction or not pumping enough volume of water thru the motor at WOT or the water pressure itself is low.

Next, the alarm at 3k rpms after sea weed problem or you have something else going on top of. Again low water pressure, sea weed or crap is causing a restriction some where in the cooling system or you have a BAD water pressure sensor or crap or (sea weed) on your water pressure sensor itself.

Next your distributor cap blew apart - Ok did someone rotate the distributor or take it out or thought it needed adjustment. You have a HVS ignition / distributor here matched with a ECM 555 - Timing is non adjustable and the rotor and the distributor need to be phased / clocked precisely. (correctly ). You might not have the rotor with distributor position phased properly or the distributor is not phased properly or both, rotor & distributor.

next and last but not least your shift in gear switch is bad or misadjusted, it could have came loose or someone hit it not on purpose.

Also forgot to add, your alarm at WOT could be your impeller housing is scared or worn - even with a new impeller, if the impeller housing has grooves in it, this will cause cavitation, hence lower volume of water flowing thru the engine and showing up during when your engine needs the most water flow (at WOT). Good luck as your fix is in one of these IMO..

On the WOT alarm, it went away without fixing anything. There was probably a good three or four weekends when I ran it WOT, I got the alarm. Then, without changing anything it went away. Pretty sure I wasn't hitting the rev limiter, it's at 5600 after the rebuild and I'm not quite there. The water thing is possible for sure. My gauge isn't accurate so I can't tell.

On the sea weed one, we cleaned out the pickups. Let her idle down to right temps and then got back to it. The alarm went off again, idled for a bit...took off again and she ran perfect the rest of the afternoon. Maybe blew some of the junk through. When the alarm went off, I could tell it went off without even hearing it yet. I was coming on plane and all of a sudden the bow slapped down. I ducked down to see if it was an alarm and sure enough it was. So definitely it pulled power. Once we got the sea weed out, it showed 100% on the scanner.

As far as the distributor goes, had it replaced and still got the alarms for a few weekends I mentioned. I just kept under 4k RPMs for those weekends and she ran great. Then without changing anything, at WOT no alarms. So I'm guessing the distributor is okay. The water idea definitely remains out there as a possibility.

On the shift in gear switch, what makes you think that it could be bad or misadjusted? Curious what symptom you picked up on.

When I rebuilt my engines I replaced both housings and impellers, probably didn't have 5 hours before got the alarm issue.

My biggest curiosity is why these alarms show up and disappear without fixing anything.