Chapter 16: Doing the Jabsco Jiggle
OK, the raw water cooling pump.
On many engines the raw water pump is belt driven. Not so on this engine. It's shaft driven off of the fuel pump drive hub.
Now a common sense design would be to make the interface between the two self-aligning.
Of course, Perkins did this but not in a way that was completely foolproof. Go figure...
The pump mounts on an adapter ring (the four inner 1/4" studs.)
The adapter mounts to the timing case cover (there's an inner ring with 5/16" studs that pass though the timing cover, and you sandwich the timing cover between the inner ring and the adapter plate.)
Here's a shot of the components:
So far, so good.
But, there's a little tricky wrinkle here. If you don't get the adapter plate concentrically aligned with the fuel pump drive hub, you run a real risk of breaking either the drive hub or the r/w pump shaft.
In the workshop manual, Perkins says you can get it close to concentric by turning the engine over a couple of revs before you tighten the adapter plate down fully snug. They do, however, recommend getting it fully aligned with a Perkins tool at the first opportunity. They also are kind enough to give an engineering diagram of that tool for those who wish to make one themselves. Now, I don't know about you guys, but I don't have a lathe in my garage. That meant hiring the job out to a shop. I got one made out of aluminum, and it wasn't cheap (but still less than a new raw water pump, so there's enough justification for me
So, reinstallation is pretty simple. Gaskets on both the inner and outer side of the timing cover, and snug the nuts down finger tight. Mount the timing cover, and insert the alignment tool. Rotate the tool to make sure it's absolutely centered. Tighten the nuts fully to secure the adapter plate. Remove the alignment tool and install the pump.
The good news is that once the adapter plate is properly aligned, you can pull the pump off of the adapter plate without screwing up the alignment. The key is to make sure you are pulling pump and NOT the adapter plate -- HINT: If you are using a 7/16" wrench, you are A-O-K; if you are using a 1/2" wrench, you are heading for heartache.