'96 Mariner 15hp water pumping issues

[Mr. Fry]

Hey guys, this is only my 2nd posting so still pretty new to this whole thing so please bare with me. I have a 1996 mariner 15hp outboard. Started it up for the 1st time this year and it runs great. But I noticed the water stream coming from the tell-tale was very weak so I figured I need a water pump rebuild, new impeller and all that. Ordered a rebuild kit, installed it and still the same problem. Weak stream. I blew out all of the lines in case it was clogged with mud anywhere but it was fine. Put a new thermostat in. Same issue. Getting very frustrated I pulled the power head out and noticed that the gasket that connects to the bottom of it was in rough shape. So ordered that and changed it. Reinstalled everything. Fire it up and it has a great stream! Shooting out like a garden hose. So I'm thinking I have the problem solved. WRONG! I tried revving up the engine and it seems that the higher the rpms, the weaker the stream gets until it finally stops. At idle it's perfect. Higher revs it's a very weak.

Long story short: I changed the impeller, all gaskets in water pump housing, new thermostat, checked pickup tube with compressed air to see for leaks. Blew out all lines and changed gaskets on the bottom of the power head. I'm at a loss for what else it could be. HELP!!

 

[flyingscott]

Did the tube fall out of the powerhead by any chance?

 

[Mr. Fry]

Nope. There's a flange on the end of that tubing so there is a housing that has to be unbolted in order to take the tube off

 

[flyingscott]

Are you sure about that? Those water tubes will come out of the powerhead pretty easily?

 

[Mr. Fry]

I am absolutely positive because I thought the same thing. Apparently not on this model anyway. I pulled on that thing as hard as I could to get it off but no go. You actually have to pull the power head out to change the tube. I tried to find a pic of it but can't. This one is similar though. There's a flange on the top end of the tube that prevents it from coming down. The housing has to be unbolted then you can pull the tube up from the inside.

 

[Mr. Fry]

I should add that I have changed all the gaskets one that housing to ensure a good seal.

 

[flyingscott]

What is the model and serial # of your motor? A 1996 model the water tube should pull right out with the water pump. Is the water tube going into the pump housing smooth.

 

[Mr. Fry]

Perhaps I'm mistaken on the year but I thought for sure it was a '96.
The tube goes in smooth and snug. There is a little sleeve that goes over it connecting it to the pump housing. The pic is all I have on it for numbers

 

[hardwater fisherman]

I believe that is a 1993 model.

 

[flyingscott]

93 is the same thing. The smooth part of the water tube goes into the powerhead. The end with the flange goes into the waterpump. I would start with your water tube is upside down.

 

[hardwater fisherman]

I could be looking at the wrong diagram but this is what I found using his serial number. It shows the water tube with a flange on top and held in place with screws.

 

[flyingscott]

Is yours a long or shortshaft motor 2 different water tubes?

 

[w2much]

Design 1 or design 2 water tube. There were bulletins issued on this subject. I just did a 1993 9.9 Mariner three times. I put O rings above and below #32 guide above on the water tube itself and below between the #29 seal and the guide. Seems to work well. My issue was that the stream was not consistently strong. I could only imagine that the water was being pushed up as it should but down below at the joints of the guide was allowing pressure to be lost therefore water would come back down or at least not have the consistent pressure needed to flow at a consistent rate through the powerhead. It did not overheat as water was circulating through the powerhead it just did not appear consistently strong at the pee hole.

 

[Mr. Fry]

Sorry for the late reply guys. I had a family issue that I had to attend to.

Anyway, I'm still having a problem with this motor. I'm not sure whether it's long or short shaft but that diagram hard water fisherman posted is the exact same as mine

 

[Mr. Fry]

Ok I think I've got something here. Which way should the engine turn the shaft. In a bout of frustration I took the lower unit off and hooked up my power drill to the shaft so I could spin it and see that's happening.
When spinning counter clockwise (which is the direction I thought the motor spun) nothing happens. When I reverse the drill and spin the shaft clockwise the water pumps out.

 

[Mohawkmtrs]

Driveshaft turns clockwise when viewing down on the top of the driveshaft.