Changed impeller, but no water...

[jpdodd]

I followed the instructions posted on the "Sticky" to install a new impeller. The old one was working, but I just bought the boat and didn't know when it had last been changed, so I decided to change it. The engine is a 1996 Force (Tracker) 120 HP. Everything seemed to go smoothly, but when I tried it out, no water. I checked the peep hole and the hose that attaches to it from the engine, and they are not clogged. I rechecked the impeller and gasket placement 2 times, and everything is good there. When I turn the shaft with my hand, the propeller turns and the "key" for the impeller is correctly in place, so the impleller should be turning. The 3rd time I took the lower unit off, I made sure that the little connecter on top of the impeller housing was fitting correct. Still no water.

I thought that it might need a little encouragement, so I tried to put it into gear and rev the engine a little bit, but still no water. Also on that note, I did notice that it didn't seem to "clunk" into gear and the prop didn't turn like it should when it was in gear. Could the problem be that the shaft is not turning? It all fit back into place nicely...

jon

 

[fucawi]

Re: Changed impeller, but no water...

Well if the prop is turning then the pump is turning ...you are always best in a drum with the water well above the pump level so you dont burn it out . Is the pipe that takes the water up to the engine in the pump outlet? ofen a 6in length of loose pipe over the outlet can be used to guide it in if you are not 100% sure...I asssume you had some water with the old impeller.
Thunk in change may just be slightly different gear shift setting when you re assembled it .

 

[jpdodd]

Re: Changed impeller, but no water...

Is the pipe that takes the water up to the engine in the pump outlet? ofen a 6in length of loose pipe over the outlet can be used to guide it in if you are not 100% sure...I asssume you had some water with the old impeller.

I'm not sure what you mean... When I raise the lower unit, there is a 3" rubber fitting which connects to the upper unit to supply water to the engine. It is extremely hard to tell for sure whether it is attached correctly due to it being inside the casing and my fingers are only so small. I'm not sure how I would get a length of pipe to guide it in where my fingers can't go... yes there was water with the old impeller.

I'm leaning more in the direction that there is some other mechanism that I either greased and wasn't supposed to, or something that didn't get put back in "just right" to cause it not to pull water up. When I put the throttle into forward the prop should have spun a lot more than it was. It was almost like it was still in neutral when it should have been in gear. Although now that I think about it, it still should be spitting out water in neutral...

I'm hoping that it is something simple that I'm not seeing, because it did not seem like that hard of a replacement process...

jon

 

[Frank Acampora]

Re: Changed impeller, but no water...

1996 should be the Mercury mid and lower unit. It should be a stainless pump. This is not the same lower unit and pump as described in the sticky.

With the pump on and the impeller in place, you should feel significant drag when you turn the shaft by hand. If not, then the impeller is not turning.

There is a coupler that fits over the pump outlet and connects to the water pipe. --now here is where I get fuzzy---In the one midleg I have, the coupler appears to be threaded on one end. It really only has ridges and this end goes over the pump outlet. The other end slides over the water tube in the midleg.

I think there is a plate under the pump body. Check to see that it is not installed upside down. Also check to be sure that the correct size impeller drive key is in there. Merc did use two sizes and you may have received the wrong one with the impeller.

If the prop does not engage in gear, then you have not attached the lower with the shift linkage in the correct position. You should have the rotating shift linkage, not the push-pull. Set the engine in neutral and then set the lower unit in neutral before attaching it. the lower unit has detents in all three positions so move it through the range to be certain you are in neutral.

 

[jpdodd]

Re: Changed impeller, but no water...

It is the stainless pump, and I used the same key that was already on the shaft for the new impeller. I didn't check the prop for resistance. I'll do that when I get home today.

I do recall there being a ridged end and a threaded end on the coupler. I'll also check that again when take the lower unit off tonight.

The new stainless plate on the bottom of the impeller was installed with the "smoother" side up and the side with the "burs" on the edge facing down. It was also the way that it fit the best. (I'm pretty sure that these are made slightly un-uniform so that if you put them on wrong it doesn't fit correctly.)

If the prop does not engage in gear, then you have not attached the lower with the shift linkage in the correct position. You should have the rotating shift linkage, not the push-pull. Set the engine in neutral and then set the lower unit in neutral before attaching it. the lower unit has detents in all three positions so move it through the range to be certain you are in neutral.

I'm not sure how to move the lower unit into neutral... There is a rotating shift linkage and a plastic washer underneath it. When I tried to turn the linkage by hand it wouldn't budge. Would I have to use pliars?

 

[Frank Acampora]

Re: Changed impeller, but no water...

Because of the detents it is very difficult to move. It is however splined on the inside to take the shift rod. I really don't remember how I did it but I suppose you could fit a screwdriver into it and turn.

 

[jpdodd]

Re: Changed impeller, but no water...

I was just reviewing a youtube video on impeller replacement and they mentioned not to get grease on the top of the drive shaft. What would happen if there was grease up there? I remember greasing the splines on the top of the drive shaft and then had some trouble getting it to go into place (had to turn the flywheel to get it to set in place). Could be that some of the grease got on top of the drive shaft...

 

[foodfisher]

Re: Changed impeller, but no water...

Probably too much grease won't compress to allow proper seating. Just paint a light coating of antisieze on the splines.

 

[fucawi]

Re: Changed impeller, but no water...

The grease just makes a seal and the air cannot get out as you push the male shaft into the female end of the engine crankshaft or it gets full of grease and the shaft wont go in ..you normally have to turn the engine to align it unless you are very lucky

 

[jpdodd]

Re: Changed impeller, but no water...

I also noticed in the youtube video that I watched, that there was a rubber "gasket" that went down over the drive shaft on top of the impeller casing(which makes sense to seal the water inside)... mine had none. Should there be a rubber gasket of sorts on top of that casing?

 

[fucawi]

Re: Changed impeller, but no water...

all the ones I have seen have an oil seal in the top of the pump housing ...me thinks you found your leak ...

 

[jpdodd]

Re: Changed impeller, but no water...

Thanks. I'll check that tonight and do some other tests and let you guys know what I find.

jon

 

[jpdodd]

Re: Changed impeller, but no water...

O.K. So I took it apart and tried to put the impeller the other way (just in case I made a mistake and put it on wrong) but it still didn't get any water moving.

SO here's what I know:

1) The impeller and key are installed and correctly and move with the shaft ( I could tell by the marks on the bottom of the housing and also how tight the key fits)
2) The shaft is turning when the engine is on, and so therefore the impeller is turning
3) The coupler from the top of the impeller housing is pretty stiff, and I would probably be able to tell if it wasn't seating properly on the tube connecting to the engine. So, I am assuming that it is fitting correctly (with the threaded end on the pump housing)
4) The hose that exits the engine and goes out the "peep" hole is clear and free of debris.
5) The 2 new gaskets (1 inbetween stainless bottom plate and lower unit, the other between the stainless bottom plate and the pump housing) are lined up correctly and installed just like I took them off.

So I'm inclined to think that there is a block somewhere that is not allowing water through the engine. But I'm not sure where that came from because it worked before (although the hose that I used did have some dirt coming out of the water when I first turned it on...)

I tried to use the hose directly on the tube that goes to the engine to see if water would come out the peep hole, but none came out. Should water come out by me trying this? Or does there have to be a lot more pressure to push it through the engine and out the peep hole?

Otherwise I'm at a loss as to what may be the problem...

jon

 

[fucawi]

Re: Changed impeller, but no water...

to confirm pump is good put gearbox in a bucket /barrel of water and spin with an electric drill ...are you sure some bits from the old impeller did not go up into the engine....blow out with compressed air or /and put your garden hose straight onto the feed pipe up to the engine and see if the water comes through ..bodge up and adaptor ....does not need to be totally leak free ....

I did have a panic on the water the other day ..a bit of wood went thrugh the system and blocked the pisser hole !!!!

 

[jpdodd]

Re: Changed impeller, but no water...

The old impeller wasn't actually in that bad of shape. Since I had it apart, I changed it anyway.

How exactly do you attach a drill to the spines of the drive shaft? I was going to try that but I didn't want to mess up the spines.

On another note, should water come down thru the engine if I force water through the hose that connects to the peep hole (push water backwards)? I wouldn't mess anything up that way would I?

 

[fucawi]

Re: Changed impeller, but no water...

No no ..feed the water up the pipe that goes into the pump . take lower unit off and fit hose to the pipe that comes down out the engine.....I often run mine like this when tuning up etc ...water should come out all the right orrifices..modern engines have a T into this pipe so you can flush them without running the motor ...

 

[jpdodd]

Re: Changed impeller, but no water...

I'll try it again tonight and let you know how it goes.

Just as a though... is it possible that the "ear muffs" don't do a good enough job at supplying water for the impeller to push up to the engine? I've read on other sites where that was the case. Now that I think about it, this is the first time that I have tried to use the muffs... it was pumping water before, but that was when it was in the water...

jon

 

[fucawi]

Re: Changed impeller, but no water...

Muffs are a waste of time ..stick it in a barrel

 

[bentle]

Re: Changed impeller, but no water...

Have you checked your thermostat? Maybe you already have done this but if not then here's another place to check. Also while thermostat is out you can try a back flush with your hose right where the thermostat opening is (motor not running) and lower off, and see if you get good flow that way. Could be junk plugging water passages under exhaust plate. I have a 94 120 force by merc. and the muffs only seem to let a small amount of water out the pee holes. In the lake though it sprays like a fire hose. You can try a barrel or drum of water but if it isn't large enough then the pump wont be able to pull the water because of to much turbulence or moving water.

 

[jpdodd]

Re: Changed impeller, but no water...

Have you checked your thermostat? Maybe you already have done this but if not then here's another place to check. Also while thermostat is out you can try a back flush with your hose right where the thermostat opening is (motor not running) and lower off, and see if you get good flow that way. Could be junk plugging water passages under exhaust plate.

I haven't checked the thermostat...Water was coming out the day before I tried the impeller replacement, so I would assume that it would be fine. I'll try the large container instead of the muffs, and then go from there. Thanks for the advice!

jon