Removing a Failed Northern Lights Generator Impeller When the Enclosure Panel Won't Come Off
You can remove the raw water impeller on a Northern Lights generator without taking the sound enclosure apart, even when the panel in front of the pump only leans back a bit. In this video, marine mechanic and ImpelPro inventor Eddie Protzeller works on a Northern Lights inline four-cylinder genset aboard a Viking yacht. A Racor filter sits right behind the enclosure, so the panel can't come off. The ImpelPro Standard Impeller Puller fits with the end of its rod pressed into the sound foam, and Eddie winds the old impeller out with a wrench.
The owner had just bought the boat and wanted to use it before a full cooling-system service in the off-season. So this job was one thing: get a failed impeller out and a new one in, so the genset runs.
WHAT YOU'LL SEE
How little room a Northern Lights genset can leave when the enclosure panel won't come off
The puller seated with its rod pressed into the sound foam
What to do when the puller slips mid-pull
What a chewed-up generator impeller looks like when it finally comes out
Why missing rubber matters once the impeller is out
STEP-BY-STEP: REMOVING A FAILED NORTHERN LIGHTS GENERATOR IMPELLER IN A SOUND ENCLOSURE
These steps follow the job in the video. The full ImpelPro instructions, including the centering warning, are here: How to Use ImpelPro Impeller Pullers.
Close the raw water valve Eddie starts with the seawater valve off before he opens anything.
Open the enclosure as far as it goes On this boat the panel in front of the pump only leans back a bit, because a Racor filter sits right on the other side. That gap is all the working room you get.
Remove the pump cover Take out the cover screws, pop out the seal, and expose the shaft.
Set up the puller Lube the threads, start with both arms parallel, and run the threaded rod flush with the bottom of the strong back.
Center the arms on the impeller Pick two impeller points directly across from each other, centered in the housing, and stay off the cam. The tool has to be centered to work. Off-center or angled, it won't pull the impeller.
Seat the tool and tighten the thumbscrew Push the arms in until they bottom out, tighten the knurled thumbscrew to set the arms, then hand turn the rod down until it reaches the shaft. In this enclosure the end of the rod presses right into the sound foam.
Wind the impeller out with a 9/16 Turn the rod with a 9/16" wrench or socket and take your time. Eddie used a regular wrench here and said a ratcheting wrench or a short ratchet would have been nicer in this space.
If the puller slips, reseat and go again Partway through, the puller slipped. Eddie reseated the arms, snugged the thumbscrew, and kept going. If the teeth don't set, go back to step 5 with more thumbscrew pressure.
Inspect the impeller and account for missing rubber This one came out chewed up with rubber missing. Those bits head downstream, usually into the hoses and the heat exchanger. Flush the hoses and check the heat exchanger before you call the job done.
Install the new impeller Install technique is its own video: How to Reinstall a Marine Impeller. For a full generator replacement including the air bleed, see How to Replace an Impeller on a Marine Generator.
ABOUT THE GREEN ON THIS PUMP
Yes, this pump is green at the weep hole, the top connection, and the inlet side. It needs a rebuild or a replacement, and the owner knows it. He had just bought the boat, wanted to use it first, and scheduled the full cooling-system service for the off-season. This visit did what he asked: a new impeller so the genset runs, missing rubber tracked down, and water flow checked.
If your pump looks like this one, the impeller gets you running. The pump still needs attention.
MECHANIC INSIGHT
On a genset in a sound enclosure, the box decides how much room you get. Here the panel leans back a bit and stops against the Racor. That leaves no room for a puller with big knobs sticking out. The ImpelPro Standard's recessed head lets it seat in that gap, and the patented bearing keeps it centered on the shaft so the impeller winds out with one wrench.
FREQUENTLY ASKED QUESTIONS
Q: Can you remove a Northern Lights generator impeller without taking the sound enclosure apart?
A: Yes. On this Viking the panel in front of the pump could only lean back a bit because of a Racor filter behind it. The ImpelPro Standard fit in that gap with its rod pressed into the sound foam, and the impeller wound out with a wrench.
Q: What size wrench do you need to remove the impeller with an ImpelPro puller?
A: A 9/16" wrench or socket. In a tight enclosure a ratcheting wrench or a short ratchet makes it easier.
Q: What do you do if the impeller puller slips?
A: Reseat it. Set the arms on two impeller points directly across from each other, centered and off the cam, tighten the thumbscrew harder, and go again.
Q: My impeller came out missing rubber. Where did it go?
A: Downstream. Small bits usually end up in the hoses or the heat exchanger. Flush the hoses and check the heat exchanger before running the generator for real.
Q: Can I replace just the impeller if the pump is leaking?
A: It can get the generator running, which is what this owner asked for. A pump that's green at the weep hole and fittings still needs a rebuild or a replacement, so plan for it.
FULL TRANSCRIPT
Eddie walks up to the generator. One side of the enclosure is already off, showing the pump.] We're down here working on a Viking with a Northern Lights genset, a little inline four. You can see how little room we have, even being able to move the side of the generator box. We have a Racor over here. So let's see what we can do. Our valve is off. Inlet, outlet up top. We'll move this cover back and see how our tool does once we get the cover off the pump. [Eddie removes the pump cover and sets the puller.] Push my fingers to get it in there. Hands on, bottomed out. We'll go ahead and tighten our thumbscrew. Our rod is very tight in here. The end of the rod is pushed against the foam, but we were able to get it in here, and we'll go ahead and see what it's like to pull it out. So I want to show you guys how tight this is. We've got the foam pushed in. That's where the rod is touching. Right on the other side is our Racor, and then in the back is our raw water. So we can't actually take this panel out. One of the great advantages of ImpelPro is how tight we can work. [The puller slips. Eddie reseats the arms and tightens the thumbscrew.] Alright, so we have our thumbscrew tight. Did not bring a ratcheting wrench, but I think that would help. So let's use a regular wrench, take our time. Let's walk this bad boy out. Slow, working just like it should. It would be so much nicer being able to put a ratcheting wrench or a 9/16 socket on here with my short ratchet. [The impeller comes out.] Yikes. Time for a new one.
RELATED VIDEOS AND GUIDES
TOOL USED IN THIS VIDEO
The ImpelPro Standard Impeller Puller. Six teeth grip the impeller hub, and the patented bearing keeps the tool centered on the shaft so the impeller winds out with a 9/16" wrench. ImpelPro is a patented impeller removal and replacement tool for inboard engines and generators, in two sizes. ImpelPro Standard Impeller Puller
ABOUT THE MECHANIC
Eddie Protzeller is a marine mechanic with more than 16 years of experience and the inventor of the patented ImpelPro impeller removal and replacement tool. He built it after watching good pump housings get damaged by the wrong tools in spaces like this enclosure.
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