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mercruiser tech question... help please

1019 Views 6 Replies 5 Participants Last post by  prop check
So the short of it 2004 6.2 liter mercruiser bravo xr drive. no probs except water pump last year. annual servicing. 72 hours. leaving marina water temp @ 150, oil @40psi, alternator out 12.8v. put the stick down rpm kick up to 4600 and the a buzzer. alarm continues till rpm drops then it goes on and off at different times. Take it to shop computer shows no faults. Cleared computer went out next day no probs. then day after no probs then at end of day alarm starts again @4800rpm and continues the 20 minutes back to marina. Engine goes into guardian mode and governs @3800 rpm all gauges stay in in good range and engine is warm but can touch all parts of it risers are cool. What do you think the problem could be ? I am going to change batteries already. All fluids are topped off. Any suggestions
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You could try unpluging the too wires that go to the stern drive gear lube bottle mounted to the engine then wait about 60 seconds to see if the horn stops going off every 60 seconds. Then also the water pressure sensor might by picking up a bad reading some place, like low water psi, air bubbles, Or in some cases the water sensor it's self might be getting a bad ground and sending the ecm a out of range reading, try looking at the water sensor and see if you can see a lot of extra paint a round the sensor, And if you have some extra wire with you try touching the sensor it's self to a good ground on the engine.
Yep.. More than likely just a sensor unplugged. Check the sensor on the LOWER water pump (sea pump) - they may have left that unplugged.

I had the same thing, and it ended up being an exh water temp sensor just unplugged and dangling. Plugged it back in and all was good.

Just go over all of the sensors that they would have touched in the process. Water pump, drive lube.
"377's" smallblocks have the water pressure sensor in the power steering cooler. (over the flywheel area) In Havasu we have seen those sensors with 'sand/rocks' stuck in the inlet hole. BUT! It sounds like you have a 'bronze pump' and they have "end cap wear problems" even with a new impeller. Get a TECH to ride with you while you have a "DDT" hooked up, that will show the NON-STICKY FAULTS. (also look in HISTORY) "Water pressure stategy" is an unprinted rule of RPMs to water pressure.
Check the pump housing front cover for wear. The brass housings tend to wear groves and that will increase the gap between the impeller and cover, lowers the pumps psi. Also check the powersteering cooler, see if it's clear of grass, impeller parts, ect... my .02 cents
thanks guys i am going to look at all these suggestions and I think the pump rebuild is going to happen tuesday. Thanks again.
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