Yamaha Outboard Maintenance-Water Pump Impellor Replacement

The two stroke Yamaha 15hp outboard. Ya gotta love the thing. There’s good a reason they’ve sold a gazillion of them worldwide. As long as you’ve got oil in the gas, it’s hard to kill them. Just about any place on the globe you want to cruise, you’ll find parts and someone to fix it if you can’t. They’re dead simple to repair and maintain. For example, to rebuild the carburetor takes me less then an hour from start to finish. The water pump impellor, which was the first time I replaced one on this motor, took about an hour and a half. Spark plugs, ten minutes. You get the idea. So anyway, here’s the pictorial of the impellor replacement.

The new impellor and the old one. The old one had been in there for at least 11 years! You can see it has taken a set..

The new impellor and the old one. The old one had been in there for at least 11 years! You can see it has taken a set..

These four bolts come out first. Two on this side and two on the other side.

These four bolts come out first. Two on this side and two on the other side.

After those four bolts are out you can start tapping on the lower unit to separate it. Once it's separated, it time to start loosening this coupling. This is the coupling that connects to the shift rod. After the coupling is unscrewed, you can remove the lower unit all the way.

After those four bolts are out you can start tapping on the lower unit to separate it. Once it’s separated just a little, it time to start loosening this coupling. This is the coupling that connects to the shift rod. After the coupling is unscrewed, you can remove the lower unit all the way.

With the lower unit off, this is what you see. That is the waterpump housing that holds the impellor. Be careful loosening these four bolts. They're likely to be corroded. Use lots of penetrant and go slow and easy.

With the lower unit off, this is what you see. That is the water pump housing that holds the impellor. Be careful loosening these four bolts. They’re likely to be corroded. Use lots of penetrant and go slow and easy.

Inside the impellor housing. Make sure it's not scored. If it is, replace the housing as well.

Inside the impellor housing. Make sure it’s not scored. If it is, replace the housing as well.

Take this cover plate off. Remember to remove the woodruff key first. It's on the other side of the shaft.

Take this cover plate off. Remember to remove the woodruff key first. It’s on the other side of the shaft.

Clean this area that's under the plate and then put the cover back on.

Clean this area that’s under the plate and then put the cover back on.

Re-assembly is basically the reverse order. Remember when sliding the lower unit back on, you may have to turn the prop to line up the splines on the shaft. When the lower unit is about a quarter inch from mating up, re-connect the shift coupler. You can move the shift lever back or forth if it helps to bring the shift rod closer to the coupling. When the coupling is tight, then you can tap the lower unit up until it mates. Tighten the four bolts up and you’re done. Easy, easy….

 

Until then….