Guardian Mode Alarm Help

[~Al]

2003 Mercruiser 4.3MPI ALPHA one Gen 2
When the engine reaches around 4000rpm constant alarm goes off and engine throttles back. Alarm silences when placed back in neutral.
Attached are pictures of errors and freeze memory

Temps stay in the 170’s
Oil pressure / level is good
Drive fluid is good
I replaced the water pressure sensor, cleared codes, problem still returned.
Any suggestions or guidance would be appreciated. Thanks!

 

[alldodge]

The key is max rpm exceeded
On the shift plate is a "in gear" switch, and if the PCM things its in neutral then when 3200 rpm is exceeded it throws the error and alarm

Unplug the switch and see if that fixes it

 

[Searay205]

Nice catch. If PCM thinks it is in neutral than 3K rpm would be over-rev. Took me a couple hours to understand since I was thinking 5K rpm would be over rev. Very tricky. Devils in the details

 

[~Al]

Great post. Will try unplugging this switch and try again this weekend. I’ll update with results. Should I expect any alarms or soft alarms with gear switch unplugged while underway?
Many thanks!

 

[alldodge]

Great post. Will try unplugging this switch and try again this weekend. I’ll update with results. Should I expect any alarms or soft alarms with gear switch unplugged while underway?
Many thanks!

No there should not be an alarm. Not positive because this has showed up before but must don't come back to close out, but it should have no effect on starting either (not part of neutral safety). The switch is closed when in neutral and opens in gear.

If that fixes it, it needs to be readjusted or maybe just leave unplugged

 

[~Al]

Great, thanks! I’ll be back to follow up.

 

[~Al]

So..unplugged gear switch, cleared history. Ran it.. ran fine until 3600rpm. Overheated to 200+\- came back checked freeze history. ECM Overheat, Engine over speed, guardian strategy, The sea pump block error did not return.
im thinking I may have weak pump in drive? Runs fine at lower rpm.
thoughts?

 

[alldodge]

If you plugged the gear switch back then that can still be the cause of the over speed

Use a IR temp gun on the thermostat housing to see if it really is overheating

 

[~Al]

I did that while out. Temp gun read 209ish on manifolds and thermo housing, matched gauge

 

[alldodge]

It was unplugged when the over speed happened?

If so, need to check continuity of the switch. See if it is open when in gear and closed when in neutral and not the other way around

Has for over heating, has the impeller been changed?
If it has, disconnect hose at the thermostat housing coming from the drive and place a short piece of clear tubing in line. Can find it at the local hardware store. Your looking for air bubbles

 

[~Al]

Just checked. It is open when in gear and closes when in neutral. It was unplugged while out, testing. See attached image of faults it gave while unplugged. I can send the detailed freeze data if helps.
the impeller has not been replaced in several years. That’s why I’m guessing that maybe the cause? If I keep it under 3k seems to be ok. When I push past 3-35k it’s not happy. Lol

 

[alldodge]

Check the wiring to/from PCM, it might be shorted to ground

For your motor, don't run it until impeller has been changed. Your pump is barely working and won't take much for it to stop and then it can be damaged

 

[~Al]

Yea. Going to get the drive serviced off season and go from there. Seems to be an impeller issue.

 

[QBhoy]

You’re over heating. That should be running in the 160’s at most. Is it the right thermostat? If you are well into the 170’s at 3000 rpm...it’s defo too high at that. Must be the impeller I’d think.

 

[alldodge]

You’re over heating. That should be running in the 160’s at most. Is it the right thermostat? If you are well into the 170’s at 3000 rpm...it’s defo too high at that. Must be the impeller I’d think.

Q don't waste your time, he does not appear to care if the motor is damaged, it all about having fun now. No worries if there is a new motor in the future

 

[~Al]

False, I’m not running it, nor having fun or risk damaging the engine. I ran it and tested it only..determined it must be an impeller issue. Returned to slip on other engine. I don’t and didn’t run the engine once high temp wa s reached. I’m fully aware of what normal range is. I’m a slip holder, will sit in slip until off season when it will be Hauled and serviced. I don’t intend on running it hot while there is a pending issue. Wanted to rule out and minor issues that could be going on.. greatly appreciate the assistance.

 

[~Al]

You’re over heating. That should be running in the 160’s at most. Is it the right thermostat? If you are well into the 170’s at 3000 rpm...it’s defo too high at that. Must be the impeller I’d think.

I agree. Will get drive serviced..thank you!

 

[alldodge]

False, I’m not running it, nor having fun or risk damaging the engine. I ran it and tested it only..determined it must be an impeller issue. Returned to slip on other engine. I don’t and didn’t run the engine once high temp wa s reached. I’m fully aware of what normal range is. I’m a slip holder, will sit in slip until off season when it will be Hauled and serviced. I don’t intend on running it hot while there is a pending issue. Wanted to rule out and minor issues that could be going on.. greatly appreciate the assistance.

:thumb:

 

[Searay205]

LMAO!!! I would be scared shitless of the over heat vs over-rev.

 

[~Al]

Just had a thought... would a blocked riser or manifold cause overheating at higher rpm? Think I will pull the elbow and riser off and inspect. :very_drunk: