Electric raw water pump?

[Epicurean]

Originally Posted by SailingHarmonie

Variable speed centrifugal pumps are not always a great answer here. You need a pump whose flow curve vs rpm gives the engine enough water at all speeds. A typical diesel as an rpm range from 800 to 4000. Not all centrifugal pumps work over a 5-fold rpm range. They also require careful engineering in the plumbing to be sure they can not get air locked, even if below water level. Significant amounts of air can come up even a deep water intake when sailing. With engine plumbing it will be a real challenge to be sure that air can rise past an installed pump.

Don't want to hijack the thread, but that is an issue I'm dealing with - air (from foam) filling the basket and then an air lock develops, causing the motor to overheat. Any solution?

[peter loveridge]

One time I ran out of impeelors in a place a long way from any sailboats. There was a commercial fishin supplies place. I rigged up a Rule baitwell pump and bypassed the belt driven seawater pump. Worked fine

[RaymondR]

The circuit is as simple as illustrated.

[kubota]

hey thats a good idea. a second
small strainer.
thanx

[botanybay]

Take a look at if pulling the pump off the engine is easier than changing the impeller in place.

On both my Perkins engines this was the case. The trick is making the hoses easy to remove. Then take off the 4 nuts holding them down, pop the pump off.

I carry a spare pump which is already rebuilt with a fresh impeller installed, swap the pump and plan to rebuild the pump if it shows any signs of leaking around the weep hole.

For Perkins the pumps are driven by the timing gears or high pressure pump cog and so if the pump starts leaking, getting salt water into the engine oil is soon to follow so I tend to rebuild the pumps when I pull them unless I did something foolish and ran it dry and destroyed it early.

With my older pumps the life of the seals is about as long as the impeller lasts (2-3 years) in southern CA with no silt in the water and it never gets cold :-)

Replaced them every season in the Chesapeake as they seemed to fail more often there.

[Onthewater222]

If you have an electric pump moving tons of water through the heat exchanger at a constant rate, what difference does it make to the engine revs and coolant flow because the thermostat is the one who is controlling the rate of coolant in the engine, the sea water can just flow through the exchanger at any amount as long as it’s at least the required amount to cool the coolant and then the thermostat does the rest.
I’m missing something or what lol

[Statistical]

Originally Posted by Onthewater222

If you have an electric pump moving tons of water through the heat exchanger at a constant rate, what difference does it make to the engine revs and coolant flow because the thermostat is the one who is controlling the rate of coolant in the engine, the sea water can just flow through the exchanger at any amount as long as it’s at least the required amount to cool the coolant and then the thermostat does the rest.
I’m missing something or what lol

You aren't missing anything some people just like over complicate things. As long as the pump has sufficient flow at max rpm you are fine. Rig it to the oil pressure switch is a good idea to avoid waterlocking the engine if you have a hard time starting. Water doesn't flow until engine is actually running if connected to pressure switch.