Redundant sea water pump.

[geomicer]

Hello. I am hoping to accomplish two things. First I wish to replace the attached sea water cooling pump on my yanmar with something modern and easy to repair/deal with while underway. I am mechanically capable and will deal with mounting etc, I am asking about knowledge on terrific pumps.

Second: I would also like to fit an independent electric pump, as the emergency as well as additional cooling when the attached pump is at idle. Same request here, I am able to handle the plumbing, I am looking for the best pump to deal with in the long term. As a sailboat, if I am using the auxiliary it's for good reason and I wish to be able to continue using it without seawater cooling casualties to worry about.

And if there are colorful stories about seawater cooling along the way, that sounds like fun too. Thank you for reading, so does anyone have a favorite pump?

[KDH]

My first question would have to be why you feel you need extra cooling on a small Yanmar in a Hunter 30? We had a Hunter 31 for a few years. I'm sure you have your reasons but may be overthinking the solution a bit. If your Hunter 30 is more than 10 years old, pull and change the mixing elbow instead. Not easy and probably near inaccessible but doable and for more bang for the buck. As for the second question, do you mean you want to go from seawater cooled to closed freshwater system?

[hpeer]

IIRC there was this guy who overwintered in the Arctic. On the way there he lost his engine water pump in Thule. He scavenged an electric pump from a school bus, or so the story goes.

I've wondered about this myself but never chased it far.

I like Whale diaphragm pumps, I think on of them would work. GE a Gulper and refit it with nitril diaphragm, it will pump most anything.

[mrcarson]

Electric pumps. Look for DANFOSS. They are very reliable.
I have a 1-1/2 in pump on my swimming pool at home. over 30 yrs old. Used regularly Another as a Bilge/cooling pump on last boat. over 15 yrs. second hand when installed.
Mate say it still plodding along.

[tkeithlu]

I'm inclined to agree with KDH here - there are other redundancies or upgrades you could design into your engine that would better protect you. Consider reviewing in your mind possible OMG situations, and attach to each a probability of actually happening to you. A failure of your existing cooling pump while motoring, and in a situation in which you cannot stop and replace the impeller, is likely to be way down the list. Do carry an extra impeller, wire tied near the pump, because they do eventually fail or there wouldn't be a market for the replacements. Inspect it every year and replace the impeller before it fails. I carry a spare impeller, and a replacement frangible link for the fuel lift pump and do in fact carry a spare electric fuel pump, because the testing of my engine showed it to be prone to breaking the links. But, it hasn't happended in the last 900 hours of engine operation.

If you do want to parallel the water pump">raw water pump, start by timing filling a five gallon bucket from the discharge, at running RPM. Then buy a pump that has that capacity in gallons per minute. Generally speaking, an impeller pump is going to be the best choice in being self-priming and supplying sufficient flow at not bunches of pressure.

[Dockhead]

In my opinion this is unnecessary complexity, which is an undesirable quality in a boat system.


I use the standard sea water pump on my 100hp Yanmar; it is extremely reliable and provides plenty of cooling under all circumstances. I change the impeller every 2-3 years or so, change the pump cover when it wears, keep an eye on it, and it's been bombproof. Never once in 13 years and more than 3000 hours has it eaten an impeller or otherwise let me down. For sailing in remote places I keep a complete spare pump on board just in case.


An electric pump is suboptimal on a propulsion engine in my opinion because the volume is fixed, whereas RPM and load on a propulsion engine vary a lot. An electric pump makes a lot more sense for a fixed RPM generator set, than for a propulsion engine.

[Dockhead]

Originally Posted by tkeithlu

I'm inclined to agree with KDH here - there are other redundancies or upgrades you could design into your engine that would better protect you. Consider reviewing in your mind possible OMG situations, and attach to each a probability of actually happening to you. A failure of your existing cooling pump while motoring, and in a situation in which you cannot stop and replace the impeller, is likely to be way down the list. Do carry an extra impeller, wire tied near the pump, because they do eventually fail or there wouldn't be a market for the replacements. Inspect it every year and replace the impeller before it fails. I carry a spare impeller, and a replacement frangible link for the fuel lift pump and do in fact carry a spare electric fuel pump, because the testing of my engine showed it to be prone to breaking the links. But, it hasn't happended in the last 900 hours of engine operation.. . .

I agree. A MUCH more worthwhile upgrade would be an alternate sea water inlet, for the case where you get a plastic bag or something in the main one. Some valves and an interconnection to another sea cock could do that.


And in general, the best thing you can do to avoid getting stranded without main engine power is not to mess with the design, but to accumulate a good set of spares. Since I sail in remote areas sometimes, I carry:


Complete spare sea water pump, multiple spare impellers, o-rings, pump cover


Complete spare fresh water pump


Complete spare hoses and hose clamps


Complete spare belts


Complete spare starter


Complete spare 2d alternator


Spare injectors and complete set of spare injector lines


Gasket set


Thermostat


Lots of fuel and oil filters


Spare fuel hose and clamps


Rig for emergency fueling out of a jerry can


Among other things.