Impeller

[headdamage]

How does this happen?

This is what the impeller in my BF45 outboard looked like today when I opened it up. The tell tell stream had been weak and when I replaced the thermostat I found an impeller vane. Turns out the vane must have been from another impeller because this one was not missing any but the vanes where going in different directions.



I used a complete Honda kit to replace all the water pump parts and replaced all the old parts. Took the boat to the lake and the tell tell was worse than before. Took it apart again and found this.



I've put it back together and now the tell tell is strong, any idea what happened when the vanes got out of whack?

[9D280]

Unfortunatley thr firewallhere isnlt letting me see the pics, but I would guess if you have bits of vane round your system one of two things have happened:

You found the first, how many others were in there, and after removing the one in the thermostat the increased flow dislodged it / them, and one laneded in the telltale port?


if the vanes were in differnet directions I guess the impeller was just rammed in instead of being gently rotated in to make sure they were all facing the right way.

[A1an]

I've never seen one do that on its own, as Ralph says it usually happens during fitting.

I put a thin smear of silicone grease around the inside of the cup when replacing an impeller, this might help in your case.

[Peter_C]

Did you back flush the entire cooling system? I too would question how many other pieces of impeller are lodged inside the cooling passages.

I have seen reversible vane pumps that flip the impellers back and forth, so my wild guess is yours should do the same, since you can see they are almost straight on the one side. Is the motor spinning backwards for just an 1/8 of a turn on shutdown? I know my backpack blower does that all the time.

[spartacus]

As suggested, lightly lube impeller and rotate in clockwise direction before dropping water pump housing on.

[henryfreston]

my thinking is you put the impeller in the wrong way in the first place, so as it spun it was forced to bend the other way?

[Peter_C]

Originally Posted by henryfreston

my thinking is you put the impeller in the wrong way in the first place, so as it spun it was forced to bend the other way?

Except if you look at an impeller they can and will flip the other direction easily, just by turning the engine over. See how on the one side the blades are almost straight?

I would still be worried about a piece of debris in the engine.

[headdamage]

I did put it together twisting it the right way and with some lube. Seems ok now though there is still some crap blocking the tel tale from time to time. Poke a wire it to it and it flows good again. What is the best way to back flush a Honda BF45?

[Peter_C]

Air pressure, and a garden hose should get the job done.

[headdamage]

Which port gets it in what direction?

[Peter_C]

I am not familiar with that engine, but probably start by removing the current impeller and blowing back thru the tell tail hose with air pressure. That should break stuff loose, but it is often the water that moves mountains...errr debris around.

[headdamage]

I took the small diameter hose adapter out of the block today and ran the engine with it out. This resulted in lots of water coming out of the block through a much larger hole. I think I got the offending bit that was blocking the pisser out. I've reinstall the adapter and reattached the pisser hose. It now looks great with lots of water coming out with good pressure behind it. Prostate fixed