pulley wheel wobbling slightly!

After installing a new raw water pump, I noticed a bit of play in the spinning of the pulley attached to the pump.

Honestly, I had noticed this before on my old pump...and I am thinking this might have been the cause of my old pump blowing a bearing, which is why I just replaced the whole thing.

after shutting down the engine, I did notice that the pulley wheel was not perfectly parallel to the other pulley wheels on my engine.

to correct this, I put a washer between the pump and the mount to make the bottom of the pump stand off a bit.

this appeared to make the pump's pulley sit more parallel...but my wobble is persisting.


could this be as simple as just tightening the belt? Although I feel like it is already as tight as the other belts.

thanks in advance.

Bri892001 wrote: Did your replace the belt as well? If the belt had some uneven wear, it could make the pulley appear to wobble, or it could be putting pressure on the pulley that varies as it goes around.

I did not think of that, but it makes sense based on the fact that I noticed the same effect on the older pump, and also for the fact that leveling out the pulley wheel did not solve the problem.

Thanks, Brian!

Maybe I'm being paranoid. could it be that, for a boat this old (96), a slight wobble may be normal?

jackkloepfer wrote: Maybe I'm being paranoid. could it be that, for a boat this old (96), a slight wobble may be normal?

No, it's not normal but stamped steel sheave are known to not run true. You had better get the dial indicator out, mark the high spots and see if you can true it with a rubber mallet. I would say you should not have more than about .010" run out otherwise you will be chewing up belts.

I'd guess you bent the sheave when removing it from the old pump. Did you have a problem getting it off?

jackkloepfer wrote: ... pete, I actually replaced the entire pump/pulley assembly. so I did not remove the sheave from the old pump

That's what was making me think it could be the belt. I figured everything was all new.

It is possible that both pulleys had a wobble, but seems unlikely. Maybe you can put your old pump pulley against a mirror or very hard flat surface like a counter top and see what you get. Of course, that doesn't totally rule out an irregularity near the shaft.

Also possible that the Crank shaft pulley is out of true and projecting the wobble. The RWP is flimsy by comparison and could get thrown around a bit.

It's worth replacing the belts anyway. The belt set is a maintenance item, and at $20 minus the discount, will probably be the cheapest thing you buy for your boat this summer: Belts at N3Boatworks