Running the engine with through hull closed

[Jlmatt]

If I want to start the engine with the through hull closed, how long can I wait to open it before the impeller burns out?

Jean-Luc

[Mo]

Jimatt,
Once your engine starts the water should be turned on. There is no set amount of time for safely running the impeller dry. Impellers are meant to be lubricated by the water coming through. I've heard of up to a minute, however I would think that repeated running of the impeller without water would inevitably shorten it's life.

That said, I've seen advertised impellers on the internet that state they can withstand prolonged water starvation....I've never had one so can't comment on how good they are. Is there something in particular that you are trying or planning to do?

[weephee]

Running the engine with through hull closed

My thinking is that the impeller is lubricated with the thru hull valve closed until the thermostat opens. The engine coolant is in a loop until then but once the thermostat opens the water is discharged and if the valve is closed then the water pump will pump dry. If I'm wrong about this then someone please correct me.
Larry

[smosher]

The standard thermostat is a bypass, which meanss that some of the water bypass's the therm and exits out. This is used to cool the exhaust.

Why wait so long, start the engine and turn on the water, alot
of folks do it that way.

Steve

[Mo]

Jean Luc
To be honest, I don't turn the water off. I'm at the boat near every day and it starts within seconds of hitting the switch. Just have to remember that if it doesn't start immediately the first thing you do is close the intake thru hull.

[positron]

I always turn off the inlet water valve and gas valve. It seems strange to not turn them on when I get the boat ready. (I do this for all my boats- sail and motor.) I usually leave the inlet valve off until the motor starts, it takes me about 5 seconds to skip downstairs and open the valve. Not sure if this harms the impeller but it has worked so far.

[Jlmatt]

Is there something in particular that you are trying or planning to do?

I'm thinking that it would be an easy way to evacuate water from the cooling system as freeze prevention. (see my other recent thread "winter in temperate climates"). My slip does not have electrical hook-up so I can't keep a heater or a light bulb in the engine compartment. I do have a T fitting at the water pump but it seems like a pain to put antifreeze in the system at the end of every sailing day this winter.
So here is another version of my question: If I close the through hull with the engine running, how long does it take to evacuate most of the water from the cooling system?

[jhwelch]

A closed pump will not evacuate any water. To do that you'd need a good blast of compressed air, then the next time you go to use the pump you'd have an partially empty block and some air pockets to contend with, so that's no solution, even if it were easy to do.

[Mo]

Hi Jlmatt,
Where are you. If you are in an area that doesn't get colder than -10C (15F) and are Raw water Cooled. When you hear the weather is getting cold.
- remove the T-stat for the winter
- use receational / plumbers antifreeze ... suck it into the engine via your T and wait until you see it spit out the stern. It will take 2 litres to do a good job for those temperatures. A four litre jug would allow you to protect twice.

An idea would be to have a Jerry Can of antifreeze ...that would be could for many many protection cycles.

Hope that helps.