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View Full Version : Help me diagnose a weird one


02ProstarSammyD
07-18-2013, 07:19 AM
Ok so 2002 merc mag mpi with 555. Ran last weekend for 5-6 hours pretty hard. Went all day with 2k lbs and a few people no issue. On the way in I came out of the no wake under a bridge hard to avoid some rollers and hit into guardian mode. For those who don't know guardian is basically the computer nazi that analyzes everything going on and tries to protect the system....


Anyways so I hit 3540 rpm and goes into protection. After that any time I went hard on the gas it just bogged and went into protection.

We threw it on the computer yesterday morning and sea water level was showing as low in the computer. Basically tore the entire cooling system apart up to the sensor. Had some slight debri in the screen right before the sea water sensor. Somehow it had made it past the check valve. Impeller was in perfect shape, pump was rotating freely, and no grooves inside.

Cleaned that out and headed to the lake. Now it only does it maybe half the time and thats if you reallly get into it. Was able to get a set in just going 75% power up to 3200 or so.

Now heres the odd part..... If I take it slow at maybe 50% throttle and get it above 3000rpm I can slam it all day long. Was running 40-42 on the way in no issue.


Any ideas? Nothing else besides the water level popped up on the scan

gotjag941
07-18-2013, 08:54 AM
Sea water low is a idiot code as well as a 3 other others like pivot low pivot high an something else

guardian mode is a protection mode in which wont allow the engine to go over 2000 rpms which can be cleared from the ECM then tested to see if you can duplicate the issue

Check all the normal things manifold temp, gear oil etc

Good luck

02ProstarSammyD
07-18-2013, 02:33 PM
Sea water low is a idiot code as well as a 3 other others like pivot low pivot high an something else

guardian mode is a protection mode in which wont allow the engine to go over 2000 rpms which can be cleared from the ECM then tested to see if you can duplicate the issue

Check all the normal things manifold temp, gear oil etc

Good luck

Temp is fine, gear oil is fine, impeller is fine, changed out fuel pump, plugs look great. Pulled out the crap in the hoses. Didn't think about it until now but gonna check the sensor contacts and clean the actual sensor up.

Jerseydave
07-19-2013, 08:15 AM
Just a guess, but if you disconnect the batteries for some time will it clear the computer like an older car?

02ProstarSammyD
07-19-2013, 09:31 AM
Don't think so but going to give that a try.