yamaha waterpump replacement

this is a 1990 250 hp yamaha i think it needs an impeller ,it overheats at low speed,water comes out the pee hole fine but compared to the other engine there is no spitting of water from the upper exaust vent <br />is it possible to do this job in the water {i would have to pay to have it hauled out }and what<br />am i looking at for parts ,lower unit gaskets,waterpump gasket and impeller? anything else?

Re: yamaha waterpump replacement

If it's been a while since the lower unit was dropped forget about pulling it off in the water. I know of somebody pulling one off standing in shallow water but that was under perfect conditions. If it's been a while the bolts and lower unit can be real stubborn. We're talking liquid wrench, heat, mallet, and patience. The shift shaft and drive shaft are splined so there's nothing to be disconnected. The water tube sits in a pump housing seal and slides out. These items can be a problem but usually are not. Pump kit is around $60. New lower unit bolts about $20. (There's one hiding behind the trim tab) Try changing the thermostat before you haul out the boat. Good Luck!<br />John

Re: yamaha waterpump replacement

I would also suspect the poppet valve and try replacing it prior to haul out. The poppet valve allows a little water circulation when the engine is cold so that the impellor doesnt get chewed. If it is closed all the way then this would explain why the pee hole is not strong. As a general rule water pumps should be replaced every 2 years! Dont skimp and do just an impellor, rather spend the extra time and a few extra bucks to get the whole kit (approx $50-60). The kit replaces all the gaskets, water tube seal, impellor and impellor cup. Would also be a great time to pressure and vacuum test the lower unit. If you have a bad lower unit seal under the water pump you already have the lower off and the pump off since this seal is under the water pump assembly. The other seal is on the prop shaft. You should have the prop removed and grease that spline also. with new thermostats, poppet valves, water pump kit, pressure/vacuum testing the lower and new lower oil you are bullet proof in the cooling and lower unit area! all that would be left is fuel filters, decarb, plugs, and timing/adjustment!!!