The other day at the beach the waves were breaking on the back of the boat and must have gotten sand into the water pick-up on my Bravo 1. Boat ran hot back to the dock (never got over 180 though). Got home removed all the hoses from the T-stat housing and flushed them. Fired the engine in the driveway on the hose and let it run 30 minutes. Never got above 130 degrees. I thought I had taken care of everything put the boat in the water today and ran fine for a while then the temp started creeping back up to about 150-155. What do you think could the T-stat have sand in it preventing proper operation? I just rebuilt the Sea water pump at the begining of the season do you think that the impeller needs to be changed again? Sorry this is so long. Any help is greatly appreciated!!! The engine is a MK IV 502MAG.
Brian

Yes, my money is on a chewed up water pump. I've seen this with many Alpha's (pump in outdrive). I believe a Bravo has belt driven water pump, but I don't see why it would have any different reaction to sand. Engine runs cool in your driveway because 1. You are feeding water under pressure into the pickup, 2. The engine is not undr any load, even at any RPM. I have zero Bravo experience, so this is only my best guess.

You may have a scored wall on the pump. This will let water pass, the hose preasure is helping the water along, when left on its own it falls on its face. The vanes are gone or the housing is bad. Get it before the vanes plug something up.

Thanks guys that is what i was thinking but wanted another opinion to make sure I did not miss something else before I dive into rebuilding the pump again.

I just went through the same thing, and had to due what Troutly was saying his tech did. I had half of the holes in the oil cooler plugged up with sand, so I removed it and had a heck of a time getting the sand out. It packs in there so tight that it is like a solid piece of rock 8 inches long. I did this after I replaced the water pump and still was getting too hot. You might as well replace the seawater pump and keep it as a spare.

Thanks guys. I just ordered a rebuild kit for the sea water pump and I will flush everything and pull the thermostat out. Should have it back in the water by this weekend if the damn parts come in. Thanks