1GM10 Engine Running Very Hot

[ianat182]

I suggest that you recheck the raw water inlet and seacock.There maybe a slotted cover on the inlet making the clearance of a weed
blockage more difficult. Try clearing using a dinghy inflator ,pump through the hose/seacock, and ensure the seacock is operating and fully open. Finally check the height of the raw water filter above sea level,if too high this can cause an air lock,it should be about 6-8" for the Vetus type.
Ianat182

 

[B58]

Overheating on GM's is usually caused by a blocked T going into the block. You will also see that there is another pipe leading from the T directly to the thermostat housing...its a bypass to allow water flow. If it stays blocked the block will receive no water and run hot...take the T out and clean the salt etc.. cooling will be restored (see diagram)