External water pump for a DF50???

[jeepster]

I have a 2000 vintage fuel injected DF50. The engine itself runs lovely but even after changing the impeller the tell tail jet is very weak and after running it for a few minutes while the jet from the tell tail turned from water to steam!
Clearly the impeller is not pumping the coolant around the engine properly, but I do not know why as this is as it has a brand new impeller?!!!
A thought occured to me...Would it be possible to use an external pump instead? An external pump could be powered by a 12V motor or even by a toothed cog meshed onto the flywheel. Such a pump could be of an extremely reliable design such as the water pump used on a car engine, which has no-contact metal impeller that cannot wear out like the stupid rubber impeller found in the bottom of most outboards. But is there anywhere on the engine where I can plumb the pump into to feed the engine with coolant water?
Obviously I will need to make a new water intake pipe, that will bolt somewhere behind the transom, to feed the pump with raw water...That bit at least is quite simple.
Has anyone here ever tried this or know of anyone that has? Examples please.
If not, I might end up being the first to try it out of desperation, as I currently have an unusable outboard!

[Harper]

I don't think your idea is sound, or at least not worth the effort.

What it sounds like you've done is merely bent the impeller vanes in the wrong direction. They have to be flexed in the correct direction or it won't pump. On the DF150/175 models, you must turn the driveshaft in a clockwise direction as you lower the pumpcase assembly over the impeller.

I think it's probably the same for your motor.

Oh yes, and also remember to insert the key in the driveshaft.

[Solarman]

There are other possibilities. Did you replace the housing, it is possible the housing is damaged, not making a good seal with the new impeller? This limits the amount of water the pump can provide.

As Harper mentioned the key, and direction of vanes is important. Also, the new impeller has to always have water on it every time the motor turns over, otherwise that impeller may fragment, water is its only lubrication.

If the water pump is working properly the tell tale should have a good strong stream. If the tell tale works fine at low rpms, but turns to steam at higher rpms (2k and above rpms), then you may have an exhaust leak into the area under the water pump, interfering with the water pump pulling water in.

You could also have exhaust leaking into the water jacket that cools the exhaust before it reaches the thermostat and tell-tale? Have you replaced the thermostat? Was there alot of corrosion in that area?

If you could be a little more specific on how it acts, and what you have done, maybe a little more information on condition of the motor, if there is excessive corrosion around the pump, etc. Then those of us at this end can help you solve the problem.

Your motor should easily pump more than enough water to cool the motor down.

Good luck, post back when able to let us know how it's going.

[ChrigelKarrer]

When a good running waterpump is working bad after impeller change then you made a mistake installing the new impeller.
It is from my experience uncommon that one thing breaks after you service it.
possible errors can be:
a) impeller housing leaking due to wrong installation or warped
b) impeller installed with fins bent the wrong direction
c) water raiser tube leaking due to wron isntallation or missing o-ring

There is a slight chance that som debris went from the waterpump in the engine block, but i would first check thruly the waterpump/impeller

Chris

[jeepster]

When a good running waterpump is working bad after impeller change then you made a mistake installing the new impeller.
It is from my experience uncommon that one thing breaks after you service it.
possible errors can be:
a) impeller housing leaking due to wrong installation or warped
b) impeller installed with fins bent the wrong direction
c) water raiser tube leaking due to wron isntallation or missing o-ring

There is a slight chance that som debris went from the waterpump in the engine block, but i would first check thruly the waterpump/impeller

Chris

Possibly option b...should they face clockwise or anti clockwise (when looking down on the top of the gearbox)?

[Murray]

Rotate the drive shaft clockwise(looking down) while pushing down on the pump case assembly.
Quoted from my service manual(2009 DF90A) Manual also recommends grease the water pump case assembly and under panel for initial lubrication.

[Harper]

Possibly option b...should they face clockwise or anti clockwise (when looking down on the top of the gearbox)?

When you do as we've indicated, i.e. turn the driveshaft clockwise as you seat the water pump housing, your vanes will end up pointing counter-clockwise.

Double check and make sure that key is still in place that locks the impeller to the driveshaft. Without it, the driveshaft just turns inside the impeller, and the impeller remains stationary.

[jeepster]

What about the paper gasket that comes with the new impellor kit? When I took my housing off before it didn't have a gasket fitted but as there was one with the kit I fitted it between the gearbox and the housing...Was this necessary or can I leave the gasket off?

[luke90046]

You may want to check the valve, water pressure
It's above the water pump