Generator Water Pump or Not?

[Madehn]

i am about to install a 10kw westerbeke gennie into my boat-- the unit is old but has been gone through mechanically with new parts installed where needed- someone mentioned that they would not use the water pump">raw water pump that is part of the gen set and just put an electrical pump on it wired to the ignition? thoughts on this ? it seems like it would work and would probably be easier to service than the impeller on the gen set. pros? cons?

[a64pilot]

After my raw water pump leaked and sprayed water all around inside of the sound proof enclosure, I removed the thing and went with a March air conditioner pump.
I see no down side, March pumps work for thousands of hours and it doesn’t pump water until the generator is making AC current so you can’t flood the generator if your cranking it too long. No impellers to wear out and clog the heat exchanger either, they are a magnetically coupled centrifugal pump.
The March pump must be located below waterline though, it won’t prime itself at all

[Madehn]

what gph March did you use?

[a64pilot]

Originally Posted by Madehn

what gph March did you use?

Forgot the number, but its the one for a 16K BTU airconditioner. That way I only have to carry one spare.
It’s a little excessive for my generator but that doesn’t seem to affect it at all. However my generator is a little 3.5 KW, so I’d first find what the required water flow rate your generator needs and of course get a pump that pumps at least that amount.
See my belief is that a generator is a fixed RPM motor, so a fixed flow pump is what you have anyway so an electric works great. Maybe not for a propulsion motor though, at idle it may be too much water.

[ranger58sb]

Originally Posted by Madehn

someone mentioned that they would not use the raw water pump that is part of the gen set and just put an electrical pump on it wired to the ignition? thoughts on this ? pros? cons?

I don't see much of a downside to a generator-mounted raw water pump, unless it's physically impossible (or at least very difficult) to get to the thing. If it leaks, it should probably have been serviced or replaced long before.

Our genset's raw water pump (Sherwood pump, on a Yanmar 3-cylinder diesel) is about the same as the raw water pump on many sailboat auxiliary engines. I haven't seen (or noticed?) many (any?) recommendations to replace the raw water pumps on auxiliaries...

-Chris

[svHyLyte]

We considered making the same change, and with a March Pump as we have one on our air conditioner that has worked reliably for years (albeit with a shot of 3-in-1 oil into the bearing channels every few weeks), as the raw water pump on our generator can be a real "pip" to service. After looking into the matter however, I decided against it because of the potential for the pump to overload the discharge system if the generator doesn't start quickly enough, resulting in raw water backing into the exhaust manifold/valves. One solution would be a "delay" whereby the raw water pump does not activate until the genny is actually running. A momentary lag between the start of the generator and the initiation of the raw water flow would be inconsequential, particularly in a fresh water cooled generator, but absent that or another solution to the potential over-flow issue, sticking with the engine mounted pump is likely the better alternative. (Of course, if you crank a genny with an engine mounted pump too long before it finally starts, you risk the same issue.)

FWIW...

[a64pilot]

My March pump is connected to the output of the generator, it’s a 110VAC pump, pump doesn’t run until AC power is made, AC power isn’t made until of course generator is up to full RPM. There is an about three second time period after generator starts until the muffler has water flow, you can hear that, but I’m sure it isn’t damaging.
My objection to a pump mounted in the generator enclosure is just that, mine failed with less than 100 hours on it, and it was the seal that failed allowing water to spray inside of the sound shield.
Recognizing that spraying salt water all over the generator could well be fatal, I decided to remove that as a possibility. I later realized that now I have nothing to check and service, and no impeller to have to replace or that can come apart and plug the heat exchanger, and that no matter how long I crank the generator I can’t flood it with water.

[svHyLyte]

Originally Posted by a64pilot

My March pump is connected to the output of the generator, it’s a 110VAC pump, pump doesn’t run until AC power is made, AC power isn’t made until of course generator is up to full RPM. There is an about three second time period after generator starts until the muffler has water flow, you can hear that, but I’m sure it isn’t damaging.
My objection to a pump mounted in the generator enclosure is just that, mine failed with less than 100 hours on it, and it was the seal that failed allowing water to spray inside of the sound shield.
Recognizing that spraying salt water all over the generator could well be fatal, I decided to remove that as a possibility. I later realized that now I have nothing to check and service, and no impeller to have to replace or that can come apart and plug the heat exchanger, and that no matter how long I crank the generator I can’t flood it with water.

Good solution we may yet adopt. I would dearly love to dump our raw water pump as it is really a pain in the neck (literally and figuratively) to service. What is the through-put on your March pump? One other question I couldn't get a handle on was the operating pressure of the engine mounted raw water pump as, if the March output pressure is too low by comparison, one could get "blow back" flow resistance at the mixing elbow due to the pressure in the exhaust manifold, no?

[HopCar]

The idea of using a remote pump to supply cooling water got started years ago when Onan installed a pump in such a way that when the seal failed water got into the engine. It was only a problem with one model but the idea seems to have spread. I don't see an advantage but as long as it moves enough water, it can't hurt.

[Privilege]

I'm watching this thread with interest. I use my genset infrequently and have to remember to run it every so often just to clear the cob-webs. The trouble is, the impeller dries out and I've already replaced it twice even though I have less than 50 hrs on the genset. It's a right pain in the stern. My thru hull and strainer are already in place for the genset so adding an electric pump would take no longer than changing one impeller.

[CaptTom]

Originally Posted by svHyLyte

Good solution we may yet adopt. I would dearly love to dump our raw water pump as it is really a pain in the neck (literally and figuratively) to service. What is the through-put on your March pump? One other question I couldn't get a handle on was the operating pressure of the engine mounted raw water pump as, if the March output pressure is too low by comparison, one could get "blow back" flow resistance at the mixing elbow due to the pressure in the exhaust manifold, no?

I also replaced my failed genset raw water pump with a March air conditioner pump. Same as a64pilot, it's powered from the generator output. Never had any problem getting plenty of water out with the exhaust. Mine is mounted outside the enclosure for ease of access.

If I had it to do again, I'd give some thought to winterizing. These pumps lose their prime so easily that just re-routing the input hose to a bucket of anti-freeze doesn't always work. Obviously pumping the A/F in without the motor running wouldn't be good. Not sure if you could "T" off before the elbow and run the A/F through backward. Anyway, that's the only down side I've found.

[a64pilot]

Except for Winterizing, I hadn’t thought about that, I don’t plan on ever Winterizing .
I can’t see a downside to the AC water pump. As far as backpressure, it should be very little on a properly designed and installed exhaust system. Around 30 in of water max, depending on engine manufacturer. That is only about 1 PSI, so a pump has to overcome just maybe a little more than 1 PSI. That isn’t much

[billknny]

Originally Posted by Madehn

i am about to install a 10kw westerbeke gennie into my boat-- the unit is old but has been gone through mechanically with new parts installed where needed- someone mentioned that they would not use the raw water pump that is part of the gen set and just put an electrical pump on it wired to the ignition? thoughts on this ? it seems like it would work and would probably be easier to service than the impeller on the gen set. pros? cons?

I would say it depends on the genset's water pump.

The water pump on my Onan is a total PITA to get to, and not because it is hard to reach, but it is buried behind the lift pump and fuel lines. A remote electric raw water pump has a lot going for it. If you want to know what size, you can use the specs, or if it is already installed catch the water coming out in a bucket for a minute.

Wiring it to the genset's power output is a good idea, just make sure the pump doesn't run if you are plugged into shore power or running an inverter.

If the genset's pump is easy to service, then don't bother.

[Privilege]

I just checked the stats on my Next Gen 3.5kw genset. It requires coolant water at a minimum rate of 180 gallons/hr, so a relatively small 300 or 500 gl/hr air con pump should be plenty.

[billknny]

Originally Posted by Privilege

I'm watching this thread with interest. I use my genset infrequently and have to remember to run it every so often just to clear the cob-webs. The trouble is, the impeller dries out and I've already replaced it twice even though I have less than 50 hrs on the genset. It's a right pain in the stern. My thru hull and strainer are already in place for the genset so adding an electric pump would take no longer than changing one impeller.

When you say the impeller "dries out" it's not the rubber than dries out, it loses prime while sitting and runs without water, that's what kills it. If you can find a way to get water into the pump chamber before you try to start it after a long down time, you'll save yourself the hassle of constant impeller changes.

Even a squirt of liquid soap in the impeller housing will lube it enough to get it started safely.