Junk in Thermostat

[araxton]

I ran aground a few weeks back and sucked up some sand. Ever since, my temp has been fluctuating from 130 to 170. I have replaced or cleaned out the thermostat three times now. Every time, it levels at 170 for a while before trapping another grain and the problem persists. Any ideas on clearing this out once and for all before replacing with clean thermostat?
Thanks

 

[moparlvr4406]

I would bet the water intake in the drive has residue
might not be a bad idea to replace the pump housing and impeller also
and while off backflush the entire system

 

[ASH]

If you actually replaced the thermostat with a new one take a close look at the old…You may need to drill 3 small 1/8 holes in the shoulder of the new thermostat to let a little water through…….I had the same problem years ago on that same engine and drilling these extra holes fixed it.

 

[CliffA]

you might want to unscrew all the blue drain plugs on the engine and exhaust and run a stiff wire in the drain hole...this will allow all the water in the engine and exhaust to drain out and using the wire will insure there is not a 'crust' over the drain hole made of dirt/sand that could reduce or stop the flow of water from that drain.....you could even start the engine for a brief period (watch your temp gauge) of time while the blue plugs are removed and let the circulating water drain into the bilge....this is one way to 'flush' the water passages.....

sand is very abrasive....if flushing the water passages does not work and there is no evidence of sand in the t'stat you may have to inspect the water pump impeller for wear, especially if it has been a while since the impeller was replaced.....if the impeller blades have significant wear they will not push enough water through the cooling system especially at higher engine rpm's.....

cliff

 

[araxton]

Thanks everyone for your input. To clarify, problem is not overheating - it's running too cool. Sounds like I need to flush the engine to eliminate any remaining sand and prevent additional clogging of the thermostat.
Appreciate the feedback and advice.