Replaced Waterpump But Still Not Cooling

[wbeaton]

I have a 1968 Mercury 39 3.9 hp outboard with a cooling issue. I replaced the impeller and checked to make sure the water passages were clear, but it still didn't pump any water. I put the lower unit in a bucket with the entire water pump underwater and turned the driveshaft with a drill. It wouldn't pump water more than an inch or so. I then replaced the entire water pump housing even though it appeared to be in good shape. It still won't pump water. What am I missing?

The driveshaft is a little rusty at the water pump. I cleaned it up with sandpaper and it seems ok. Could this be causing a loss of pressure? Any help is appreciated. I've never run into this before.

 

[Laddies]

Re: Replaced Waterpump But Still Not Cooling

I think this is the problem
http://forums.iboats.com/showthread.php?t=241666

 

[wbeaton]

Re: Replaced Waterpump But Still Not Cooling

Thanks for the reply, Laddies. However, the problem seems to be that Its not pumping water in the first place. When I got the motor is was completely apart in a box. I checked all the water passages and blew air through them at that time. I didn't see any restrictions at that time. The rubber gromet where the intake tube meets the powerhead base was fine. The old impeller still had all its fins. I can blow air up the intake and it comes out the exhaust. When I put the drill on the driveshaft it barely moves water, unlike other water pumps I've tested. That is the part that gets me. Why is it not pumping water? Even if the passages were plugged the waterpump should still shoot a good stream of water when submerged in a bucket. The waterpump is completely underwater. Any thoughts?

 

[CharlieB]

Re: Replaced Waterpump But Still Not Cooling

The 9.8 uses an inlet water tube with a grommet, ensure that tube/grommet are in good shape and that the inlet screen is not covered with growth.

You didn't drop the impeller key as it was going together?

Sometimes we overlook the obvious as we KNOW that we just fixed that, re-check everything very carefully.

 

[Laddies]

Re: Replaced Waterpump But Still Not Cooling

Wayne, if you have done the pump and it don't pump with a drill, stick a short tube in the pump outlet and slowly submerge it while running with a drill when it starts to pump properly thats the level of the vacume leak. The most common place is the pickup tube, if pried out of the grommets they tend to bend and won't always seal properly I always seal them with sealer 1000 after installing in place. I have had a couple that had to change the housing on that lookrg great but still won't pump, thats the same pump as the little twins so you know how they should pump. Bob

 

[wbeaton]

Re: Replaced Waterpump But Still Not Cooling

I used the new gromets on the pick up tube, but I didn't seal them. The tube took some prying to get it out so maybe that's the problem. Thanks fellas.