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Discussion Starter · #1 ·
Looks like I will be needing to replace the impeller on my Merc 5hp. Or at least the outboard is not peeing.

I have the replacement kit.

Anything special I need to be aware about? Is this a tricky job? First time doing this.

Thanks for any advice.

jballou
 

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islander bahama 24
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Nothing tricky to it its rather straight forward the only thing to watch and insure its correct is the proper direction of rotation on the impeller also I find that a spray with WD40 works great to facilitate the installation of the new impeller
 

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Around here, any stoppage involving a small hole should be checked to rule out mud dauber infestation. These pests will fill any small hole with their mud nests, spiders and their eggs/larva. I have to clean out the discharge hole on my little British Seagull outboard every spring and as necessary throughout the summer.

Have FUN!
O'
 

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Great! Thanks. Anything else that could be preventing water flow through the pump that I should check out?
No experience with your motor. On mine the thermostat could get plugged up, but there was a small by-pass hole in the housing, allowing a small bit of water to pass, maybe not enough to flow out the pee hole. Checking the thermostat might be easier than changing the impeller. Or, if the motor is not overheating, the pee hole may be plugged? Pulling the head to check for plugged water passages may also be easier than changing the impeller.

I have changed a few impellers and found that getting the water feed tube back into the power head was challenging. Finally figured out that tipping the motor upside down made it a lot easier to see what I was doing.

Paul T
 

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islander bahama 24
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The five HP merc its easier to change the impeller however a length of bailing wire into the pee hose would clear any minor blockages also the pee water is derived from the exhaust cooling water check the impeller first they should be inspected annually anyway (ounce of prevention and all ) also the water cooling feed line boot is in the lower unit on the little mercs.
 

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Discussion Starter · #7 · (Edited)
OK - thanks everyone for the useful comments. Impeller has been replaced - not difficult at all!

But now I am having trouble re-inserting the lower unit back into the drive shaft housing. Unit will go in until it feels like the drive shaft is bumping up against something - about 3" short. So the drive shaft is not going in enough. Gear shift is in reverse.

Any ideas on what might be the problem and how to solve it would be greatly appreciated!

cheers - jballou
 

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OK - thanks everyone for the useful comments. Impeller has been replaced - not difficult at all!

But now I am having trouble re-inserting the lower unit back into the drive shaft housing. Unit will go in until it feels like the drive shaft is bumping up against something - about 3" short. So the drive shaft is not going in enough. Gear shift is in reverse.

Any ideas on what might be the problem and how to solve it would be greatly appreciated!

cheers - jballou
It is possible that the splines are not lined up on either, or both, the power head or gear box. With the spark plug removed, try turning the engine over, slowly and then the prop with it in gear. I hope you did not take the shaft out of the gear casing as it may be difficult to re-insert it? No experience with your particular motor, but IIRC on OMC motors, the gears may "mis-align" when the shaft is removed.

Paul T
 

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Discussion Starter · #11 ·
Oh my. The saga continues. Replaced impeller, put it all back together. But still no pee stream.

Any other suggestions?

I think this outboard has decided that its role will not be to putter a dingy around, but to teach me about outboard mechanics instead...!

Thanks - as always.
 

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Oh my. The saga continues. Replaced impeller, put it all back together. But still no pee stream.

Any other suggestions?

I think this outboard has decided that its role will not be to putter a dingy around, but to teach me about outboard mechanics instead...!

Thanks - as always.
Oh dear, back to the drawing board. First thing to check is it heating up? If you see steam coming out of anywhere, it is likely the flow is being impeded.

After running for a while you should be able to touch most parts of the power head without burning yourself. Better yet, use a hand held infra red heat sensor. Anything over about 160 degrees is suspect.

Check the pee hole with a wire, then check the thermostat, put it in a pan and bring up the heat. It should open at about 140 to 160 degrees. there may be a small bypass hole in the thermostat housing that should be open.

If there is a lot of debris / deposits in the thermostat housing the other water passages may also be plugged. Last resort is to pull the head and clean them out as best as you can.

Or, maybe, you installed the impeller backwards? even so, it should/may pump some water? A good shop manual should show the proper mounting specs. Make sure the water feed tube from the lower unit to the power head is clear. I had a Johnson 6HP 2 stroke that plugged up right at the power head to lower unit joint because when the motor was tilted up it didn't thoroughly drain out. Try the easiest things first.

Let us know what you found.

Paul T
 

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Did you check that there are no rubber bits of the old impeller stuck in the exits and or lines from the pump???
 

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Did the pee hole stream just suddenly quit, or was it gradual? If suddenly, likely something got past the intake screen, or as above, maybe a broken impeller blade?

If gradually, could be salt build up, or, as mentioned, bugs or wasps.
Just remembered, if yours is a four stroke, don't take the head off until you have completely explored all other possibilities. I think it is doubtful that all the water passages in the head are blocked. Maybe restricted somewhat, but probably not all blocked solid.

First thing to do is to see if it is over heating as previously described. Over the years I finally learned to see if there was fuel in the tank before ripping the engine out. "Easy things first". :D

Paul T
 

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Oh my. The saga continues. Replaced impeller, put it all back together. But still no pee stream.

Any other suggestions?

I think this outboard has decided that its role will not be to putter a dingy around, but to teach me about outboard mechanics instead...!

Thanks - as always.
Heh I'm going through the same thing with a recent craigslist purchase of a Merc 3.3 two stroke. Except on top of the lack of water pumping it also had a stuck carb and broken shear pin.

My fault for taking it without seeing it run (he had paperwork from a year ago showing service and hadn't used it since. I still believe him, but my bad)

My water output just slowly drips. I've taken the impellar apart and it looks great. Blowing air into the output hose some goes through, but there is a lot of resistance.
 

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JB, I have a Tohatsu 6HP 4 stroke, maybe the same basic engine you have? It has a fitting to connect a garden hose to. If you turn the water on & you get a stream out of the pee hole, it is likely the impeller or a plugged thermostat housing. If it is passing water out the exhaust, probably the same?

If your motor doesn't have a fitting you might try the "ear muff" type of flusher. In either event, don't turn up the pressure up very high, it might back up into the exhaust system & come in past the exhaust valves.

Maybe, if there is some obstruction or debris in there the hose water might flush it out?

But then that would be too easy? :D

Paul T
 
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