Changing engine mounts on our Northern Lights generator

We're anchored in Palm Beach, where we'll be for the next two weeks at least, and I am using the downtime to get some projects done around the boat. Today's project was to replace the two engine-end mounts on our Northern Lights 16kW generator, model M844K.3, and I thought I would write it up here in case anyone in the same situation finds it useful. This post will concern nothing else, so if you are not interested in generator maintenance, feel free to skip it. I will return to our regular travelogue, including the details of what we are doing here, in the next post.

If you arrived here from a link on a forum or social media site, or via an Internet search, welcome. To answer the inevitable questions about what kind of boat this is in, you can find the details of our boat at this link. We've lived on the boat full time for a little over a decade now, and we spend a majority of our time at anchor or at free docks without power. The generator sees a lot of use, averaging about two hours a day when we are not under way or connected to shore power, and now has over 6,200 hours on it, about 5,100 of that during our ownership. It was installed when the boat was first built, back in 2002.

Bad mounts removed. You can see where the engine brackets have sunk into the rubber.

Apart from regular oil, filter, and impeller changes, and the occasional valve adjustment, major maintenance I have done has included rebuilding the injector pump twice -- they seem to go around 2,500 hours before they start leaking, so rebuild number three is on the horizon -- rebuilding the seawater pump, and replacing the coolant pump. I'm currently wrestling with a minor fuel leak in the return line at the injector pump, so you will see some fuel staining in the photos.

What the front mount looked like before I started. The engine bracket is sinking through the rubber.

Recently we've been noticing a lot more rattling around the boat when the generator is running, and when I could not find a specific source I decided it's time to tackle a long-overdue project that I have been putting off for way too long, namely, replacing the engine mounts. I've been watching the engine brackets slowly sinking into the rubber mounts for at least a year now, and while that may not be the entire cause of the rattle, it's certainly not helping anything.

There are four mounts for the entire generator set; two are at the engine end, and two at the generator head end. The two at the generator end appeared to be in decent shape, while the two at the engine end were completely deteriorated. In part that is due to exposure to engine fluids, but it may also be due to more vibration and more weight at that end. I elected to just replace the two engine-end mounts at this time, reserving the generator end for a future date if needed.

Exploded view from the parts book. Lower left are the relevant parts. Copyright: Alaska Diesel Electric

My parts book shows several different part numbers for the mounts. I first had to find the page for my specific generator head, which is a PX-316K, and then find the engine end of the frame on the drawing. The call-out (#5) for those mounts showed different part numbers depending on whether or not a PTO is fitted. Ours does not have a PTO, and the correct part is a 220-lb Parker-Lord "Plateform" mount. I was able to find the Parker-Lord part number, 283P-220, but this is an industrial specialty item with only perhaps three distributors nationwide. Fortunately, the local Northern Lights dealer, a short $2 bus ride away in Riviera Beach, had them in stock for a fair price of $88 each.

Brand new mount in hand, with close-up of the manufacturer part number.

With two fresh plateform mounts in hand I started noodling on how to unload ~440 pounds from the existing mounts in order to make the swap. I spent some time on the phone with my go-to guy at Northern Lights, eastern region service manager Joe Maas, who is a wealth of information and has saved my bacon more than once, mostly regarding our Lugger propulsion engine. The call was about the fuel leak, but as long as I had him on the phone I got his advice on removing the mounts; he shared that he's used everything from crowbars to bottle jacks, which gave me some confidence I was unlikely to hurt anything.

It's cramped in our enclosure, but the boat builder left a pair of skyhooks in place directly above the factory lift points on the generator set. I don't know if they had incredible foresight regarding future maintenance, or if they were just leftover from the original installation, but I was glad they were there and decided to use the one above the engine for the purpose. They had even left bow shackles on both strong points. My first attempt involved hanging our Warn half-ton portable winch from the shackle, but the winch turned out to be too long, hook to hook, to fit, with less than an inch of winch cable showing above the hook on the engine.

I considered jury-rigging different hardware on the winch to make it fit, but in the end decided to order a cheap quarter-ton manual chain hoist, sometimes called a "come-along," for overnight delivery from Amazon to a locker nearby. If I had more room I would have ordered a half-ton model instead, for a bit more safety margin, but the cramped quarters persuaded me to go with the smaller hoist.

550-lb chain hoist suspended from shackle on ceiling. The lift ring on the engine is obscured by the enclosure frame.

I was able to get just enough leverage on the hoist to lift the engine most of the way to where it would be on the new mounts. I had to lever the engine block up with my Gorilla bar to get the last click on the hoist ratchet. Then it was a "simple" matter of removing the four bolts holding each plateform mount to the frame, and the two bolts holding each L-bracket to the engine. The whole assembly of the plateform mount and L-bracket needs to be removed from the base frame in order to remove the through-bolt holding the mount to the L-bracket, as the bolt head is inaccessible with the base frame bolted down to the boat.

I put "simple" in quotes because, of course, it was a challenge. I started with the front mount, where I could see what I was doing; all the in-place photos are of this mount. The identical mount on the rear of the engine must be accessed from the end, since that side of the generator is against the wall and the back panel is fixed in place. If you look at the "before" photo you will see that the mount is so badly crushed that it is overhanging the four mounting bolts. I could not get a socket on six of the eight bolts no matter what I tried.

Here the weight is already being taken by the hoist, but the rubber is still so deformed I could not get a socket on the bolts.

The two front bolts I could remove with an open end wrench, and for the rest I needed to use a crow's foot. That was pretty straightforward on the front mount, but involved a lot of "boat yoga" and a handheld mirror on the rear. The bolts holding the L-brackets to the engine came off way easier than I expected, suggesting they were not properly torqued.

Bracket and mount removed.

Once I was able to pull each of the mounts out of the base plate -- I did the whole replacement in the front before I started on the back -- I discovered that the original installer had installed them upside-down. The bottom of the mount is flat and the top has what looks like a little volcano in the middle, and that volcano needs to point up. This most likely contributed to the mounts' early demise, and now that I know they did it wrong it looks like the two at the generator end are also upside-down. That might incent me to change them sooner rather than later, or maybe just flip them over. I also learned that snubbing washers, shown on the parts diagram on both sides of each mount, were omitted from the top side on all four mounts. I did not have these on hand so I had to put it all back together without them.

Here it is. This is actually the rear one, which better showed the "volcano" that is supposed to be on the top actually pointing down. That's the snubbing washer below it. The rubber from above the plate has extruded through, pushing part of the mount down at left in the photo.

Once I had each mount/bracket assembly in hand I was able to remove the through-bolt and nylock holding them together When I assembled the new mounts to the brackets I snugged up the nut but did not torque fully because there is a bit of play in the bracket hole, and the mount and bracket would likely need to move relative to each other at least a hair to get all the mounting bolts to line up. That involved levering the engine laterally relative to the base frame with the Gorilla bar while trying to start the threads with my free hand. It was a fiddly process but I eventually got them all in. With fresh mounts I was able to use a 13mm socket on the bolts holding the mounts to the base frame.

New mount, correctly assembled, pointy side up. The lone snubbing washer is on the flat bottom; this is a fail-safe, which keeps the generator from coming out of its frame altogether if the rubber fails.

The generator is now a lot quieter, and I'm wishing I had tackled this a bit sooner. If you have one of these sets, inspect your mounts. The specific plateform part numbers may be different, but the replacement process is the same on most Northern Lights generators up to 20kW.

New mount installed and in service.