Generator impeller replacement
My trusty and reliable Cummins-Onan generator switched itself off after running for just a couple of minutes. The blinking error code on the main switch told me that the error was “High Temp” and I knew that my impeller had once again
decided to separate into it’s constituent parts. I decided to bite the bullet and replace the impeller, a task that I hated to do because access to the generator is so restricted but which needed doing. I budgeted an hour, that was
yesterday at noon. It is now 17:00 the next day and the task is finally completed.
When I opened up the raw water pump all that was left of the impeller was the central core, every single impeller blade was gone, broken off at the root! Naturally, these small bits and bobs had been pushed down the tubing into the
heat exchanger and I had to access that in order to use my trusty dental picks to get those bits out and prevent the system from clogging up. Easier said than done, since the oil filter blocks access to the intake end of the heat
exchanger. Since that oil filter is at the bottom of the engine, it makes for less mess to drain the oil from engine before removing it.
It was time for an oil change anyway. My trusty little oil filter removal tool didn’t fit in the limited space so after doing all sorts of experiments with other tools and methods I finally poked the filter with a screwdriver (yes, it is messy) and
after the mess had drained I finally got the old filter removed. The mess in the genset pan took a shile to clean up, but once that was done it was a simple to remove the end cap of the heat exchanger but since access is miserable,
I had to poke around blindly to get the bits out and lying there with head, arms and shoulders below the floorboards while the occasional roll hit the boat was no fun at all.
But in the end I got everything removed and replaced both end caps. Getting the new impeller into the pump took some doing; I had a system worked out from the previous time but for some reason the backing plate wouldn’t let the third of three mounting screws get installed. In the end it turns out that the orientation is important and the logical mounting position doesn’t work. So, after about 4 hours total time I finally had the whole system put together again, with a fresh oil filter and clean oil and a cleaned heat exchanger downstream of a brand new impeller. I fired up the generator and saw that the water flow was great – but that a lot of it was staying in the pan of the generator!
It seems that one or perhaps both of the heat exchanger gaskets had blown and were letting a lot of water out. By this time I was tired and had run through my whole selection of expletives at least twice (my little fantasy of forcing the engineers to actually work on their creations won’t every come to fruition, I fear) so I turned off the raw water seacock and had a happy hour libation prior to dinner.
I have two raw water inlets, one large and the other even larger. One is for the engine, the other for the genset. Stupid me, I assumed that the larger diameter was for the engine. The little drip in the genset compartment had let quite a lot of water in, and it the central bilge area where the genset is located doesn’t drain to either my forward or my aft bilges! Since I couldn’t get more than an arm into the opening, getting this water out was going to require either a lot of time with a rag or implementing some sort of a pump that would reach down there. Sigh…
I ended up renting a car so that I could drive to the Cummins-Onan dealer on the island, ELECTEC, and got 2 gasket kits (at $36 a piece not the cheapest components). I used my oil pump to drain the 20 liters of water from the compartment and then spent some more time with rags and absorbent pads getting as much of that nasty saltwater out as possible before replacing the gaskets. I did have to drain a lot of my fresh engine oil so that I could spin off the filter and remove the heat exchanger endcap, but I’d purchased some extra oil to make up for what I’d removed. Oil is certainly slippery and messy, though.
I was somewhat nervous when I primed and started the generator and it was with more than a little trepidation that I checked the generator pan with a flashlight for fresh leaks…. luckily the new seals had done the trick and I was once again ready to go.
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