Help please with 2003 Merc 5.7 Mag Bravo 1

[cobalt79]

My new to me Larson with 2003 Merc 5.7 Mag engine overheated after launch a couple of weeks ago. It has closed cooling with a thru hull intake. We are thinking that this intake may have gotten plugged with seaweed because as soon as the boat started moving the temp went down. No overheating for the next week, but if we let the revs stay at 1200 rpm the alarm would go off and the engine would power down. If you power thru that 1200 without triggering the alarm the engine runs fantastic. It seems as if we have triggered a sensor code that will not resest, and have taken it to a mechanic who says that the scope shows that no codes have been tripped and is confused himself.

Anyone have this happen to them? Any input would be greatly appreciated.

Thanks
Jack

 

[Don S]

Re: Help please with 2003 Merc 5.7 Mag Bravo 1

Have you checked your raw water pump impeller? It may have been damaged during the original overheat.

 

[cobalt79]

Re: Help please with 2003 Merc 5.7 Mag Bravo 1

Don:

Wow, thanks for you quick reply, never thought of that. The running temperature is always good though. Could the impeller still be a problem, this is all new to me.

Jack

 

[tpenfield]

Re: Help please with 2003 Merc 5.7 Mag Bravo 1

The sea water pump leads to the oil cooler, and that is where the seaweed usually gets stuck. Check the inbound side of the oil cooler for blockage.