Water pump rotation

[Lee Scott]

What is the direction of rotation of the Sherwood water pump on a Universal M18 diesel engine? I'm replacing the impeller on mine, and when I look at at the original impeller before removal, it appears that it rotates counter-clockwise, from the direction the vanes are slanted.That just doesn't look right to me, though. If it's rotating counter-clockwise, the vanes are rotating toward the raw water inlet on the upper left, and away from the outlet on the lower right. I can't see how it could pump water that way. The brass cover is not a lot of help, as it shows the pump rotation in both directions.If it rotates clockwise, why are the vanes all slanted toward the direction of rotation??? I'm cornfused!

 

[Stu Jackson]

A trick I used just last week

is to turn the engine over with the impeller in the pump and see which way it goes. Pull the stop handle up, have a mate turn the engine over for two nanoseconds and you'll know for sure. If you don't have a replacement impeller, take the old one off the shaft, reinsert the shaft, and watch it closely. Also, once you know, make a note of it in your engine maintenance log so you don't forget for next time.

 

[Ken Juul]

Impeller

It doesn't matter. I too was worried about the direction until I helped a dockmate. His pump had the impeller mounted inside the housing with a sealing plate on the front. Stuck in the old one vanes pointing in different directions, put it in with them all in the wrong direction, etc. Within one revolution of the pump they were all aligned properly. I am sure it is easier on the vanes if it is installed properly, which I do when changing at the dock. But if I have to change it bouncing in a seaway, what ever is quickest is the key. It also helps to slather them in vegetable oil, help lubricate until the water gets flowing. To determine which direction the pump turns if you don't have a helper, pull the "T" handle to ensure the engine won't start and turn the engine by hand. A wrench on the alternator pulley usually does the trick. Turn it so the cooling fins on the pulley are biting the air, from memory it is clockwise looking at the front of the engine. Doesn't take much to determine the direction. Use a scribe or sharp nail to scratch the direction in the pump housing for a quick reference.

 

[Lee Scott]

Thanks,

If the vanes will align themselves within 1 revolution, then I guess it doesn't really matter which way I install it, other than it's probably easier on them if they don't have to do the flip. The marine surveyor reported that the engine ran a little warm at full throttle, so I'm trying to make sure everything's OK in the cooling department. The old impeller is missing a piece of 1 vane, and the radiator cap needed to be replaced, but that's all I've found so far.

 

[Stu Jackson]

Did you find the missing piece

of the vane? They don't just disappear...if it's in the hose or HX then you need to get it out, or you may continue to slightly overheat.

 

[Lee Scott]

Not Yet

I haven't started the search for the missing piece of vane yet. It's a pretty small piece that broke off, so it's probably lodged somewhere in the heat exchanger. I'm not sure how to find it other than to just start taking things apart. I may wait and see if the engine still runs hot before I start breaking things I can't fix. After all, the gauge itself might be off.The lake I sail on is small enough that I need to worry more about making sure I run the engine long enough to fully warm it up than I do having it overheat.