Mercury 3.9hp won't pump after impeller change

[Wiggy]

I've recently changed an impeller on my bosses old 1965 Mercury 3.9hp and now it won't pump any water whatsoever.<br /><br />I've blown through (both ways) the cooling system with high pressured air. Checked that the impeller is locked with the key on the driveshaft, and this turns when turning the driveshaft.<br /><br />It was pumping (but badly due to a wrecked impeller) before, so why not now?<br /><br />Any ideas?

 

[sport15]

Re: Mercury 3.9hp won't pump after impeller change

Are you sure that the uptake tube seated in the top if the water pump housing and is there a new seal on the uptake tube?

 

[grew14ft]

Re: Mercury 3.9hp won't pump after impeller change

Are you sure the impeller fins are bent the right way inside the pump housing? Not sure if it would pump water if the fins were bent the wrong way.

 

[Wiggy]

Re: Mercury 3.9hp won't pump after impeller change

There isn't a new seal on top of the tube (I think) and not sure about the impeller fins either.

Which way should they be (looking down on them from above)?

Also, where's the pee hole on this motor?

 

[AMD Rules]

Re: Mercury 3.9hp won't pump after impeller change

The pee hole is under the lower cowling at the rear. Don't pull that water tube out of the mid-section or you'll go crazy trying to get it back in without removing the powerhead. Its not straight, and curls back under the powerhead exhaust plate.

To install the impeller, grease/oil/soap the housing then rotate the drive shaft clockwise from above as you lower the housing into position. The rubber vanes will end up pointing to the left, when viewed from above.

Did it pump water before the impeller change? Did you change the pump housing gaskets too?

 

[Wiggy]

Re: Mercury 3.9hp won't pump after impeller change

My boss said that it pumped water before we change the impeller, and that was with a extremely worn and cracked impeller!

There's something obvious I'm missing here, so I'll have another go at it tomorrow.

Thanks for all your tips and replies....