5.0l mercruiser bravo 3 overheat

[sessasells]

other than the obvious broken water pump belt. Engine is pumping 20-27 psi water pressure, but heats up to 190 in about 20 minutes at 2500 rpm, then alarm fires off and I shut down the engine for 15-20 min to bring temp to 180 until it runs hot again. Can thermostat not be opening all the way? Other suggestions?

 

[MarkSee]

Re: 5.0l mercruiser bravo 3 overheat

When was the last time the water pump itself was serviced/replaced? Know for sure the impeller is intact? Not sucking any air? Any leaks?

If you do some searching in the forums you'll find there can be several other issues causing your condition, just to start:
-thermostat stuck open or missing can cause issues
-corroded exhaust manifolds/risers
-head gasket, exhaust manifold to riser gasket
-something partially blocking the water flowing through the coolers
-water circulating pump

Mark

 

[tpenfield]

Re: 5.0l mercruiser bravo 3 overheat

Yea, I had a problem with sea weed, etc. making its way through the sea water pump and collecting at the oil cooler. I finally resolved it by backflushing the oil cooler. Then added a sea water strainer before the sea water pump to prevent future occurrences.

So, I would check for clogs at the oil cooler and see what you find.

 

[mcginnal]

Re: 5.0l mercruiser bravo 3 overheat

other than the obvious broken water pump belt. Engine is pumping 20-27 psi water pressure, but heats up to 190 in about 20 minutes at 2500 rpm, then alarm fires off and I shut down the engine for 15-20 min to bring temp to 180 until it runs hot again. Can thermostat not be opening all the way? Other suggestions?

Hello. I just purchased a 2003 Monterey with a Bravo III 5.0L from a previous owner. When the boat is in idle (i.e. first launch and tied up while pulling the truck off the ramp), my coolant temp rises past the thermostat limit switch (~160F) to upwards of 200F. I find that if I rev the engine for a few seconds, the higher RPMs drive the cooling water pump faster, and the temp will drop from ~200F down to 150F. I'm still investigating my problem, but it may be either a blockage or vapor lock in the pump at idle.

Does your overheat occur during normal operation, or just idle?

 

[spdracr39]

Re: 5.0l mercruiser bravo 3 overheat

Hello. I just purchased a 2003 Monterey with a Bravo III 5.0L from a previous owner. When the boat is in idle (i.e. first launch and tied up while pulling the truck off the ramp), my coolant temp rises past the thermostat limit switch (~160F) to upwards of 200F. I find that if I rev the engine for a few seconds, the higher RPMs drive the cooling water pump faster, and the temp will drop from ~200F down to 150F. I'm still investigating my problem, but it may be either a blockage or vapor lock in the pump at idle.

Does your overheat occur during normal operation, or just idle?

sounds like your impeller is bad.

 

[MarkSee]

Re: 5.0l mercruiser bravo 3 overheat

Does your overheat occur during normal operation, or just idle?

Welcome to IBOATS mcginnal, a great place to get help.

What you really need to do is open a new thread of your own which will get you the most help possible; and follows the rules of the site.

Mark

 

[mcginnal]

Re: 5.0l mercruiser bravo 3 overheat

Welcome to IBOATS mcginnal, a great place to get help.

What you really need to do is open a new thread of your own which will get you the most help possible; and follows the rules of the site.

Mark

I wasn't bringing up my issue as a hijack; I was sharing it as a comparison. The quote you linked from my post was me asking the OP about his issue, actually. I didn't think that was against forum rules?