merc 9.8 water pump

[fishmonger.33]

hey. ive got a mid 70's(i think) 9.8 hp merc. there is no water coming out, i have taken the lower end off, and checked the waterpump, and made sure everything is connected, but it just keeps shooting a steady stream off air, where could it be taking air in?? and what should i try to fix it, is there possibly a vacume problem somwhere? any help is much appreciated, thanks again...

fishmonger33

 

[emckelvy]

Re: merc 9.8 water pump

Try removing the lower unit and connecting a source of water to the copper water supply pipe. This will tell you if you have any circulation problems in the upper end. I'm thinking you'll find things OK, since you report you're getting air blown out the telltale.

If you indeed have good water flow thru the powerhead, here's a few things to check on the water pump end:

1. Is the plastic "guide tube" present? This tube fits in the top of the upper water pump body and helps guide the copper water pipe into the pump body. If you don't have the guide tube inserted into the pump body, it's real hard to get the copper tube properly inserted as you're installing the lower unit.

2. Is the rubber water tube grommet inserted into the pump body? If this grommet is not present there will be no seal, and water likely will just blow around the copper water tube with none getting to the upper end.

3. Is the impeller key properly installed? It's quite difficult to get these back in place properly (I use a dab of sticky grease to hold the key in place while inserting the impeller as you simultaneously rotate the driveshaft). Easy to check, pull the upper pump body and rotate the driveshaft. Either the impeller spins or it don't!

4. Are the impeller blades all curled up, or are they nice and flexible so that they maintain continuous contact with the stainless water pump insert. The impellers on these have such short blades, that it's very common so see the blades take a 'set' from sitting in one position. The side that's all 'curled up' won't uncurl as the impeller spins. You'll get little or no water pumped if that's the case. Solution: install a new impeller!

Anyway, that should cover all the bases, check it out and report back with the results. I bet you find something!

HTH.......ed

 

[fishmonger.33]

Re: merc 9.8 water pump

thanks, ill try those things, the guild tube is there, and they copper tube coming down is connecting, i think it may could be like you said, and that i may need a new impeller, it has been in storage and taken a form, it isnt very flexible anymore. ill be trying that today thanks

 

[fishmonger.33]

Re: merc 9.8 water pump

oh, and any good sites for finding the year?? the serial no. is 7151683. is it an 83'? or is there another way to tell, i was told the motor was older then this. thanks,

fishmonger33

 

[warpedrotor]

Re: merc 9.8 water pump

I have a similar problem, I just tried a Merc 9.8 (similar serial number) I bought over the winter. As a precaution, I changed the water pump impeller. Running it in a barrel, no water came out of the tell tale. I traced that problem to what seemed to be a piece of aluminum stuck in the tell tale nozzle. I had to drill it out. I also found that there was no thermostat installed. Now when I start it (still no thermostat) I get exhaust and hot water coming out of the tell tale. The motor looks to be in excellent shape, previous owner claims about 10 hours use. There is 90 Psi in each cylinder, it runs normally in the tank.
Could I have screwed up the impeller installation or could it be the exhaust baffle or gasket leaking...

 

[lupien]

Re: merc 9.8 water pump

2. Is the rubber water tube grommet inserted into the pump body? If this grommet is not present there will be no seal, and water likely will just blow around the copper water tube with none getting to the upper end.

HTH.......ed

Where should that grommet be exactly? Maybe that is my problem. I will try shooting water up the copper pipe to see if it comes out the telltale. If so maybe that missing grommet thin is the cause but I`m not sure of where this grommet should be.

Thanks