Generator raw water pump losing its prime

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Ortolan
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Re: Generator raw water pump losing its prime

Post by Ortolan »

ADDING A WATER TEMP GAUGE

As a footnote, I had wanted to upgrade my Northern Lights control panel to their more "deluxe" one, which includes gauges as I liked the idea of having a water temp gauge. Unfortunately the panel is quite large & over $500!

A tech at Northern Lights told me that since a water temp sender is factory installed AND the wire harness already contains the lead, all you really need is a standard $30 gauge. So for $30 & an hour of time, I now have a gauge above my old control panel to observe the water temp, which should help foresee most cooling failures, rather than solely relying on the auto shutdown.

If anyone would like the wiring details, let me know.
Russ
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Expatriate
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Re: Generator raw water pump losing its prime

Post by Expatriate »

My gen set was not losing prime on the seawater side, but it was overheating after about five minutes. Basically just enough time to warm up. Of course I checked oil and water before I started it the first time. It overheated and I replaced the raw water impeller. Then tried it a few times, no luck. The belt was loose so I tightened it and tried it a few times. No luck. I replaced the overtemp cutoff sensor and tried it a few times. No luck. I was all ready to replace the thermostat so I checked the coolant again. It was a quart low!

When I checked the coolant overflow tank, way in the back, it was completely full! Good grief, what a simple problem to solve I thought. It had to be the radiator cap, but it looked brand new. The gasket is nice and soft and the spring is still stiff. So any expansion overflow goes into the tank, but is not siphoned back to the engine after it is shut down. That got me thinking back to previous engines. I had never seen an engine with overflow down that low. It is not designed to siphon back. No way. Looks like it was put there merely to prevent pollution. I figure that all of my test runs of five minutes each may have pushed out some coolant, but not a quart. Maybe a cup in the worst case. So now I think it was a little low on coolant and I blew it. The impeller definitely needed replacement, and the belt was loose enough to turn the pulleys by hand. The radiator cap is allowing too much overflow. The sensor was probably fine, but now I have a spare. All these things conspired to confuse me!

In any case, I have purchased a new radiator cap and an after market overflow tank. I will mount the tank high up and forward. The old one will just have to stay put. I could not figure out how to get it out and it really won't matter anyway. The new tank has the hose connection at the bottom so it should drain easily back to the engine header tank. When I topped off the coolant, the gen set ran like a sewing machine for about a half hour while we celebrated with a beer.

Any one else seen this?

Tim Denney
MV 068 Expatriate
BuoyScout
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Re: Generator raw water pump losing its prime

Post by BuoyScout »

We're having similar problems, but have some unique symptoms I haven't seen in the thread. I'm hoping the strainer behaviour is a consequence of another issue described here:

Generator Stalling / Sea Strainer Bubbling & Draining (Northern Light - LUGGER - M673D.3)


HISTORY:
- Underway (at slow speed) running the genset for about 15 minutes and it shut itself down.

- After about a half hour it was started back up. Ran for a couple minutes. Then shut itself down.

- When checked, the strainer was pretty clean, but no water in it. Changed the impeller, and primed the strainer. Ran for a bit, the water in the strainer dropped to close to empty, so we shut it down, topped up the strainer again, started it back up and the strainer water level dropped again. After about a minute the genset shut down again.

- Checked and appears the genset is getting a free flow of water through the hull.

- Tried to pour water in the strainer without the generator running... drains right out through the hose through the hull (takes about 15 seconds to drain).

- Watching the closed sea strainer while starting the generator we see water being drawn up into the sea strainer. BUT the water level immediately drops to almost empty (but not dry) when genset is started and while running.

- Tried having the sea strainer open with the garden hose pouring into it while the generator starts up. It draws more water out of the sea strainer than the hose can supply. Impeller appears to be working fine.

- Genset is shutting down very quickly (about 1 minute), and while there’s still some water in the strainer. (Cold engine)

- We did discover the fuel transfer valves in the cabin we left on accidentally. We turned them off and the generator ran for 30 minutes, then shut itself down again.

- Checked the valve by the fuel transfer location in the hatch in the front deck.

- tried again a few hours after the last test. It shut down after about a minute.

- Confirmed the intake to the strainer is clear (snorkelled and cleared with wire + can see water coming into strainer + can blow air down to thru hull).

- Confirmed impeller is sucking water in (couldn’t fill the strainer fast enough with 2 freshwater hoses filling it as it ran)

- Installed new sea strainer. Ran for 10 minutes before stalling.

- Checked for loose connections/hardware.

- The strainer is never able to fill while running, and appears to have bubbles in it as its filling.

- Fuel filters replaced. Ran for 15 minutes before stalling.

- Oil and filter changed. Ran for 5 minutes before stalling.

- Hoses from seacock to sea strainer and hose from strainer to impeller replaced. Ran for 2 minutes before stalling.

NOTE: Running time before stalling varies from 10 seconds to 20 minutes.

NOTE: Noticed a consistent sound as tests were repeated. The sound is a quick pop (sometimes multiple pops) of what sounds like air escaping OR being drawn into the system. The sound is there when the genset starts, and is also there as it stalls. Location of the sound couldn't be determined.

NOTE: After stalling, the sea strainer bubbles (from the engine side of the strainer), and drains empty out the through hull.


QUESTION: Can anyone identify what/where the sound is when starting and stalling?

QUESTION: It seems like the issue is air getting in the system between the through hull and the strainer. But having replaced every component (with the exception of the seacock), I'm questioning that obvious looking conclusion. Any thoughts? Additional troubleshooting suggestions?


PS - New (to us) PDQ34 owners, and new to the forum. So excited to be here. We've heard (and already have seen here) so many great things.


Josh
Vagabond|Hull 35
Josh + Karen + Dutch
SCOUT, Toronto ON, Canada
2004 PDQ MV/34
Hull #035
duetto
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Re: Generator raw water pump losing its prime

Post by duetto »

hi,

i'll say up front that i don't have the later generator water intake /exhaust. a fellow pdq owner with the newer genset setup had a similar problem a couple of seasons ago. in that case we got it narrowed down to an air leak where the water intake exited the tube built into the hull. you might want to check that joint, maybe put liquid detergent to test for leaks.

what i find amazing is that a garden hose can't keep up.

good luck.
john & diane cummings
duetto mv34 #23
chrishead
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Re: Generator raw water pump losing its prime

Post by chrishead »

Just throwing out here that our fix to the strainer draining was to insert a short piece of PVC pipe about 3/4 of the inside height of the strainer and seal it into the strainer inflow hole. The strainer now holds water to the top of the pipe. Also, we had recurring shutdown issues and did the usual cleaning of the heat exchanger and removing impeller pieces from the hose to the exchanger from the pump. It ran fine, but then a relatively new impeller failed after about 20 hours. A few blades were cracked, but the impeller was still intact. It turned out there were impeller pieces in the hose from the strainer to the pump, probably from before our purchase. So always check both hoses, not just the downstream one, unless you are sure you have all the fragments.
Julie & Chris Head
"Headway"
2006 MV 34 #86 100hp
dstrecker1
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Re: Generator raw water pump losing its prime

Post by dstrecker1 »

I have not had a problem with my generator water pump, but after reading the post I made a device to fit inside of the raw water strainer that would retain water.

Dennis and Cindy
PDQ 34 2006 hull95
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James Power
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Re: Generator raw water pump losing its prime

Post by James Power »

Have a look at Vetus water strainer # FTR 140. They have the same idea.

James
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Re: Generator raw water pump losing its prime

Post by BuoyScout »

A long overdue update (I didn't have notifications turned on):

We brought Scout (formerly Vagabond) into Winter Harbour on our way home in June. Unfortunately one of their jrs spent 10+ hours trying to figure it out, and eventually called in someone else who caught it in a half hour. It turned out to be a simple 15A DC breaker that was intermittently making or losing its connection as the generator vibrated.
15A breaker failed.jpeg
15A breaker failed.jpeg (38.1 KiB) Viewed 823 times
Granted, the second guy didn't have to review everything the first guy went through, but man, that was an expensive fuse to replace.

Wiggle your wires (Charlie's best advice). Lesson learned the expensive way.

And thanks for the replies everyone!

Josh + Karen + Dutch
Josh + Karen + Dutch
SCOUT, Toronto ON, Canada
2004 PDQ MV/34
Hull #035
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