Northern lights 20 kw generator overheating/shutting down

[ValhowellPower]

Need some collective assistance. New to us boat. Generator temp sensor replaced due to leakage at the base. Raw water pump replaced due to leakage at bearing. First time using generator since then. Generator shut down due to overheat after about 10 minutes of operation.

We are at anchor so troubleshooting is limited.

Impeller plate hot to the touch.

Let engine cool down. Removed impeller cover. Impeller is intact. Confirmed impeller turns when engine cranked.

Cleaned salt water strainer and back flushed intake line to ensure intake is not blocked. All appears good. Let engine cool and tried restart. Gen exhaust on GB49 is at water level. Hard to confirm good water flow.

Shut off gen manually as temp approached 200 degrees.

Hose from raw water pump felt soft. Hard to tell if there is good water flow.

My ideas for next steps is to flush water from raw water exhaust to exhaust elbow to confirm heat exchanger on the salt water side not clogged. Then remove and test thermostat.

Other ideas? Thanks for the assist.

 

[luna]

I also have a water level exhaust exit that is under the swim grid making it impossible to see the flow.

If you have a see through bowl type of strainer body you could try shining a light thru and watch for the movement of the bubbles or sea grass to get a feel as to the flow. Or how about red food coloring in the strainer while at rest and then watch it disappear as you start the engine. It should be quick.

If your Ocean temperatures are different than the air temps you should be able to feel the difference in the temperature of the bronze piping once the engine is started. This and the light is what I use to establish flow.

Have you felt the shower head elbow at start up? Does it stay cool or get hot quickly?

Before I started flushing I would remove the exhaust hose at the exhaust elbow to ensure that the shower head holes are not plugged and that the hose from there to the exhaust exit thru hull runs clear.

 

[Comodave]

It may not have a prime. The impeller may turn but if the sides of the impeller or wear plat is worn it might not pull a prime.

 

[Lepke]

You should always carry a spare impeller.
It could be the impeller is hard and not sealing correctly. If the plate is hot you weren't pumping water.
When I replace an impeller or inspect an impeller, I grease the inside of the housing and plate. It helps seal and draws water better. Greasing the inside is recommended in older engine manuals, before the EPA. Waterproof grease is better.

 

[ValhowellPower]

Thanks for the input. Pump and impeller are brand new. I will check flow at the exhaust elbow and see what we get.

 

[O C Diver]

I would look down stream of the pump to the heat exchanger. There are some owners that replace an impeller and don't look for the broken blades down stream. Also, the tubes get plugged over time and need to be periodically cleaned. Water has to have a place to go for the pump to prime.

Ted

 

[UrsusMaritimus]

I had a similar issue with my NL generator. Some time back, I had an impeller failure, and after replacing it, I cleared the broken chunks of impeller from the heat exchanger, reassembled, and thought I should be golden. But… it would run an hour or so and shut down due to high temps. I have a water sep exhaust, so can’t see the water discharge. Turns out, I had water flow, but it was impeded by a chunk of impeller jammed in the hose between the raw water pump and the heat exchanger. Removed that, and no more issues.

 

[Maerin]

You likely have an obstruction in the raw water piping. Check it from strainer thru the entire circuit. Use of a small shop vac (like a "Stinger") is helpful to isolate and test sections of the system. Pull the caps on the exchanger to inspect the tube ends. I'd suspect the exchanger or the downstream from the pump.

 

[eddieclemons]

I have the same generator and had the same problem once. The problem was almost like melted and extruded impeller parts coming out the discharge end of the heat exchanger. A rod would not push them out. I took the the exchanger out and took it to shop for cleaning. All good afterwards. Good Luck.

 

[Dean Russell]

The absolute expert on Northern Lights and Lugers is
Bob Senter
Northern Lights/Lugger Service Training
cell: 360-531-1444

 

[ValhowellPower]

Actually problem solved. Northern lights certified mechanic installed the new raw water pump upside down. His issue…my $$$. 7 hours of trouble shooting on my part and three hours to fix. Mechanics reaction was…”sorry, my bad. Glad you were able to fix it”. Never again on my boat.

 

[Diep]

That's terrible. Paying an expert is the main benefit of the $$ to have someone else do it. You didn't get the pleasure of saving the time or the trouble.

I hope to never make mistakes like that but occasionally something only goes right the second time. Hearing this at least helps me cut myself a little slack.

 

[tiltrider1]

This is exactly why I don’t like letting other people work on my boat. They tend to create more problems for me than they solve.

 

[Hobbit]

I have the same generator and have found for some reason the hose that comes from raw water pump into heat exchanger corrodes and almost plugs….also the hose coming in has plugged before as well. I had this problem this year after replacing impeller just last year…this gen doesn’t get used that much we have a second 12 kw that’s used all the time.