Generator water intake obstruction

[John&Ria]

I’ve just begun the process of breaking in a new Northern Lights generator. The first 7 hours went fine, however today the generator shut down automatically after about 5-10 minutes of operation. I believe this was likely due to overheating as I discovered a heavy concentration of seaweed in the strainer bowl. After clearing this out, letting the generator cool down, and rechecking the oil (it was fine), I restarted the generator. No relief, as there is no indication of water entering the strainer bowl or exiting the underwater muffler (I.e. no bubbles). Although it may be possible I fried my impeller (unlikely, as it’s virtually brand new and the shut down occurred pretty quickly), I believe I must have a blockage somewhere in the intake system.

This is a new situation for me, so my question is whether anyone who has experienced a similar blockage has had success in clearing it themselves while the boat is in the water, and if so, how did you do it?

Any and all advice will be gratefully received.

Cheers,

John

[makala]

Take a garden hose and backflush the strainer- hold the spigot tightly to the strainer intake hose and it will blow out the intake line. This occasionally happens but is a quick fix. Once its blown out you will hear bubble sounds coming up the hull.

Thx,
Doug

[duetto]

if the garden hose doesn't work, don't discount a bad impeller. remember shutdown occurs when the engine temp reaches overheat set point. at that point there has been no water flowing (cooling impeller) for quite some time.

good luck.

[John&Ria]

Thanks for the suggestions. I’ll give the water hose a try. Others have suggested using air pressure from a vacuum or dinghy pump, so I might try that too.

If no success then I’ll have a look at the impeller. I’ve not done that before. It looks like it’s easy to access, however can one get a good look at it while it’s in situ, or does it need to be removed?

[duetto]

take the following with a grain of salt, since i don't have a nl.

if you can see the pump cover and remove it you'll be able to see impeller. no water could mean the rubber broke loose from the metal hub, so if you can turn the impeller on shaft with needle nose pliers it spun off hub. you'll also see if you have missing blades.

good luck.

[John&Ria]

Thanks John, I'm pretty sure I can spot the cover plate for the pump at the front of the engine. It seems to be held in place with a few screws that look readily accessible.

I'll post an update - hopefully favourable - when I get a chance to investigate this issue later this week.

[John&Ria]

Today I had an opportunity to investigate the overheating issue with our new generator. Some of the potential causes were likely eliminated, however I think the cooling system is still being restricted somehow. I was able to use the air pump for our dinghy to ensure the intake passages to the screening bowl are clear, so no issues there. Next I checked the impeller and it looks fine to me (picture enclosed). Once everthing was reassembled the generator was started and we looked for the usual bubbles under the hull that demonstrate the system is working. Only a few bubbles were evident, however there was a noticeable and persistent discharge of what I would describe as brown clouds of fine debris. As pictures tell a thousand words I've enlcosed as series of pictures that were taken as the generator started up and ran for a short period.

The debris clouds have me wondering if we have a blockage somewhere downstream of the engine. Perhaps elements of the muffler or the discharge pipes are breaking down? To my knowledghe, these parts have never been replaced, but still look to be in good shape to me.

This one has me stumped. I would welcome further ideas or suggestions on what to do next, before we have to meet with our friendly mechanic again.

Thanks!

[duetto]

did you let it run for say an hour? i think you need to see if it can run the way you would use it. if it passes the run test then worry about the clouds. also, i assume you have the o-ring for the pump cover.

[John&Ria]

John, thanks for the additional comments.

I've not yet run it for any length of time. The appearance of the debris clouds was/is a concern that I may be doing some kind of damage to the system, however my mechanic - who quickly responded to my email, even though it was Saturday night - has also advised that I should now try and let the generator run. He also advised to check the temperature at the exhaust hose between the water lift muffler and the Vetus separator. He says if there’s no water coming through there it will get warm. When I get back to the boat that will be my next step.

Yes, I made sure the o-ring went back on the pump cover. No leaks when we ran the generator .

[makala]

The impeller vanes are backwards on a few of the vanes (impeller is ruined) you will need to replace the impeller. Recommend checking the water exit hole using your finger. I would use a garden hose to backflush the intake- if there is a large obstruction air could feasibly pass by but not much water, so using the dinghy pump could be misleading


One other possibility comes to mind- check the hoses at the strainer and make sure the strainer nipple did not collapse when/if someone overtightened a clamp. This happened to our old strainer but it still operated ok. But this could easily make the generator pull in air intead of cooling water.

Cheers from the Berry Islands and good luck!
Doug

[John&Ria]

Doug, appreciate you joining in.

Interesting comment about the impeller vanes. This is a first time with this for me and I'm not familiar with what's right or wrong. My mechanic did not say anything about the picture of the pump, but perhaps he did not look at it closely. In any event I have a couple of spare impellers and will replace the current one. Is there any special tool needed or will gentle extraction with a pair of needle nose pliers be sufficient?

When I used the dinghy pump I removed the hose from the bottom of the strainer and then inserted the pump fitting into it. It was a perfect fit and permitted full power into the hose, without leaks. We got strong air flow and bubbles from under the boat with this technique, and I'm quite confident there is no obstruction there. At reassembly I inspected the bowl and ensured everything was tightly double clamped - coudn't spot any leaks there or elsewhere in the system. That said, when we start the generator again I'll do another close inspection.

Have fun in the Berry's! In 2014 we stopped by there on our way from the Exhumas to the Abacos - it's a great place to hang out.

Cheers,

John

[makala]

You can ease impeller off using two pairs of pliers 180 degrees apart and rocking them back and forth.

I would replace impeller and then check the cooling water exit hole- a lot of times barnacles/oyster-like stuff tries to grow in there. Use a flat head screwdriver to clear it.

Any recommendations on things to check out in the Berrys? We just got here

Thanks,
Doug

[James Power]

Replacing the impeller may help but I wouldn't be concerned about the couple of vanes oriented the other way. When diesels shut down they will frequently jump backwards a few degrees. The vanes will correct themselves on the next start up.

James

[John&Ria]

James, thanks for the clarification about the impeller blades. Once less thing to worry about while I sort out this generator issue.

Hope all is well.

Cheers,

John

[John&Ria]

Doug, when we were in the Berry's we stayed at Great Harbour Cay Marina, which we liked a lot and can recommend (decent facilities and very good wifi, which was not always easy to find in the Bahamas 10 years ago - it may be better now). My recollection is there were some excellent beaches on the west side of the island, within a reasonable distance of the marina. Unfortuately we did not have an opportunity to anchor out in the Berry's, however I understand from others there are excellent places to do so there.

Have fun!