Occasional solid alarm/guardian issue

[metsfan3197843]

I have a 2004 5.0 MPI (OM656133) that occasionally goes into guardian mode just as I'm easing out of no wake speed. The alarm is solid and I have to shift to neutral to clear. If I put the hammer down instead of easing the throttle up it doesn't go into alarm. I have not had it happen at any other RPM range, and it doesn't always happen easing out of no wake speed either. I've read a lot of old posts and am leaning towards the sea water pressure sensor but thought I'd throw it out to this awesome group of much more experienced boaters. I live on Kodiak Island in Alaska and we do not have a Merc dealer and I have now been able to find anyone that can check the ECM for codes

Thanks for any input or suggestions
Kevin

 

[alldodge]

I'm thinking the in gear switch (item 24) might be the cause. Starting just a bit after your serial number the switch was removed (0M656000 and higher). The link below shows the Alpha shift plate and if you have a bravo then there will not be the shift interrupter.

The switch tells the motor its in neutral and if rpms go to high the alarm sounds and guardian mode is set.
To test the theory, unplug the switch and give it a try

http://www.mercruiserparts.com/bam/subassembly/31849/8093/295

 

[metsfan3197843]

Awesome thanks! I'll give that a try and report back. So if that is the issue and merc. stopped using the switch does that mean no need to replace it just heat shrink off both connectors and call it good?

Thanks so much for suggestion

 

[alldodge]

Awesome thanks! I'll give that a try and report back. So if that is the issue and merc. stopped using the switch does that mean no need to replace it just heat shrink off both connectors and call it good?

Yes, it was more trouble then it was worth

 

[metsfan3197843]

Finally got out to try the fix. Issue is still there, only worse today. Usually just hammer on the throttle and all is good but today after a half dozen tries and the alarm coming in and cutting the power I limped on back to the dock. Looks like I'll be ordering some software to figure out what the issue is. I'm thinking the software is the way to go, not the tool. I'll post the results afterwards to try and help out anyone else having this issue

 

[alldodge]

With these new PCM's it would be a good investment

 

[metsfan3197843]

I agree. I'm thinking over the long haul it will pay for itself. I ended up getting talked out of the software and just ordered to tool. Kinda weird to have the salesman talk me into spending less....

 

[metsfan3197843]

Just an update for anyone with the same issue. I got the scan tool in and found the culprit to be sea pump/blk pressure low alarm. cleared all alarms and put the boat in the water today hoping to have the issue and watch things with the tool plugged in. And of course the engine ran fine....

The sea water psi reading was nice and stable and climbed nicely with RPM. I was getting about 12 psi at 3600 RPM. I'm leaning back towards a flaky sea water psi sensor. I'm going to try and launch again tonight and see if I can get anything to act up

 

[alldodge]

Check to see that the sensor has a good ground. The PS cooler is bolted to the block, so check there all good a tight

 

[metsfan3197843]

Thanks for the tip. Bolts are good but I did notice a ground stud on the port side of the engine I hadn't noticed before (In my defense I've only had the boat a few months!) that has 4 or 5 ground wires attached to it that is pretty nasty. It's really hard to trace the wires from the sensor because of the tight space but the harness runs right towards that. Any chance the sensor grounds there or is it strictly through contact where it mounts? Regardless I know I need to clean it up but it looks like its going to be a real bear to get too, like pretty much everything on this particular boat/engine set up

 

[alldodge]

Sensors either get the ground from the block or have splices inside the harness. Anything on the block (wires/cables) is for battery, Mercathode and galvanic isolation (if you have one)