While not an Onan, I took my raw water pump
off after it failed and fitted a March airconditioner pump a few years ago.
factory installations have an electric pump feeding the impeller pump, to me that’s ignorant, but I can see how they may have to do that to protect the generator warranty.
Anyway if you wire the March pump directly to the electrical
output, fused of course, then it won’t begin to pump water for a few seconds until after the generator starts, so the generator will run for a few short seconds with no water, this hurts nothing and you can hear the exhaust
note change when the water begins flowing. The water flow also stops well before the generator winds down too, meaning the exhaust
system is blown clean of water during shutdown, so even if your sailing in heavy weather
the water in the exhaust system can’t flow back into a non running motor
You cannot overcrank the generator and fill the motor
with water, because there is not water flow unless there is electricity.
The March water pumps however must be below water line, they will not self prime at all, however their life span is usually in pretty much decades and tens of thousands of hours. Think of how many hours they run in boats sitting in a marina with the AC on 24/7 for years.
I have used a Globe dry run impeller in my main engine water pump
, in my opinion they work
fine, but it seems due to the greater hardness of the blades that they caused more water pump wear, that is an impression, I can’t verify it.
For a main engine you need a variable flow water pump as the engine varies in RPM
so an electric pump would be tough to fit, so they may not be a good idea there.
But for a fixed RPM
generator I can’t see any reason not to fit one, and they put an end to water pump maintenance
, once installed you forget about it, there is never any need to change anything, of course carry a spare pump.
This is the strainer I installed to catch impeller vanes on my main engine, I once tried an after market budget
impeller, and yes it soon came apart, so after having to disassemble the heat exchanger in a deserted anchorage, I fitted the strainer.