93 Fountain twin 502 efi"s. Up untill last fall we stored it in a cave so we never did anything to the cooling system for winter. Last year I had to winterize. I took the thermostats out and let the engine pull the antifreeze in. I had a bucket filled with coolant and hooked it to the fresh water flush and closed the valve to the lower unit. Both engines pulled the coolant right in. This weekend I put the stats back in and took the boat out. Both engines went to about 190 so I turned them off. I checked the water shutoff valves to make sure they were in the correct position and they were. So I'm thinking the sea water pumps have gone bad. But both at the same time? Waited a few minuets and restarted. Now both water pressure gages have came up to a few pounds at idle and the temp gages went down. Under way temp and water pressure now seem normal. Here is the question. Is it possible there may have been an air pocket that caused this problem? Both engines acted exactly the sam. I am going to order new impellers anyway.
Thanks for any help.

Jerry.

A very easy way to test impellers is to remove the belt and turn the raw water pump pulley clockwise. You should not be able to turn them easily. If they spin freely, your impellers are fried. Be sure to get all the pieces of the old impellers out.

You could be right on the money with the air pocket theory.

Probably had air in the top of the engines.

I think if the impellers were gone I would never have gotten any water pressure and the engines would have continued to over heat. Allthough it seems the sea water pumps should have quickly filled the engines. I have new impellers on the way but at this point I think they just had some air traped.

Thanks for the input.

Jerry.

I agree. The thermostats were in an air pocket and did not sense heat right away. That allowed the engine to heat up more than normal. After sitting, the thermostat got warm enough and opened. Drilling a couple of small holes in the edge of the thermostat allows the air to escape and makes the temp generally more even.

I was surprised the stats did'nt have an air bleed hole. I have seen them on some applications.