1978 Mercury 800 80hp Water Pump

[Sean Leonard]

I replaced the water pump impeller on my 1978 Mercury 800 80hp. The lower housing was easy to remove but now when I try to reinstall it there seems to be something wrong. It will go on then stops about an inch or so from mating. I'm obviously doing something incorrectly but I don't know what to do to get it back together. Any tips?

 

[impatico]

Re: 1978 Mercury 800 80hp Water Pump

Just some guesses here but try turning the prop while doing pushing? make sure the water tube is lining up with the water pump, if it got bumped it might be off a bit and hitting the top of the pump housing instead of going in the hole?

 

[Sean Leonard]

Re: 1978 Mercury 800 80hp Water Pump

Well, we finally got it in. Now it's acting like it's in forward all the time. The prop only turns clockwise when the gearshift selector is moved to forward, nuetral and reverse. I thought i followed the manual to the letter but I guess not. Any thoughts?

 

[Chris1956]

Re: 1978 Mercury 800 80hp Water Pump

Sean, This is a common problem. Drop the gearcase and use a crescent wrench to gently turn the shift shaft CCW until it clicks into neutral. Prop will turn now both ways. Now set the throttle lever to neutral. Put some grease on the driveshaft and the shift shaft. Now install the gearcase. Turn the flywheel a bit until the splines align. A needlenose plier will help align the shiftshaft. Wiggle it into place tightening the nuts with your fingers only until it it touching. Now use the wench to tighten.

 

[Sean Leonard]

Re: 1978 Mercury 800 80hp Water Pump

I am assuming the shift shaft is the splined shaft on the gearcase. Is that right?

 

[aussieflash]

Re: 1978 Mercury 800 80hp Water Pump

Yes the small splined shaft is the shift,the large is the drive shaft.I just did mine in neutral and had same problem,about 1/2 inch out.So i slid it out a little and turned DRIVE shaft a fraction CW and it slid straight in.