new impeller/housing failed - 99 Mercruiser 7.4mpi bravo 3

[swaldrum]

So i decided to replace my impeller and housing this year as a pre-emptive strike. Haven't done it before but got a bunch of info from this board and i have the seloc manual. (1999 mercruiser 7.4L mpi/bravo 3)

pulled the pump out and opened it up. The existing one didn't look too bad so figured i'd keep it as a spare.Put the new impeller into the housing and reassembled everything. Put it back in the boat.

Fired the engine (on muffs) and never got any water coming out. Shut it down, pulled the pump back off and opened it up. (ran for about 30s)

The impeller blades clearly melted and left ridges on the housing. Smelled of burning rubber/plastic.

Put the old impeller/housing back in, fired the engine and all was good.

Going to pick a new impeller kit up on monday, but in the meantime any ideas why i fried the new impeller/housing?

I double checked everything when i put the old one back on, only things i can think of:

1. maybe i put it on upside down? and was pushing water out instead of pulling it in? I don't think the bracket would allow that would it?
2. When i seated the impeller in the housing it was extremely tight compared to the old one??

any ideas would be appreciated since i would rather not do the same thing to another new one....

thanks,

Scott

 

[Don S]

Re: new impeller/housing failed

Re: new impeller/housing failed

Welcome to iboats, but man, you really need to tell us what you are working on, other than a boat. Merc, Volvo, OMC, year, engine size, etc. You know, just the minor things.

 

[swaldrum]

Re: new impeller/housing failed

Re: new impeller/housing failed

sorry about that, had it in the body of the post but not the title. Fixed the title so it should be more obvious.

1999 Mercruiser 7.4l mpi w/ bravo 3. and yes it is a boat

 

[Don S]

Re: new impeller/housing failed

Re: new impeller/housing failed

Look very carefully at where the intake and outlet hoses go on the pump. They are very easy to mix up. Especially if the pump has to be replaced using one hand only, and the brail system.
Don't ask how I know that.

PS: You have a LH rotation engine, and the directions are on the pump housing.

 

[swaldrum]

Re: new impeller/housing failed - 99 Mercruiser 7.4mpi bravo 3

it's definitely hard to see what your doing in there so i'm guessing i got the hoses backwards. The pump is clearly labeled, i'll just make sure i get it right this time around.

do you generally lube up the impeller when you fit it in the housing? if so, what do you use?

scott

 

[Bondo]

Re: new impeller/housing failed - 99 Mercruiser 7.4mpi bravo 3

do you generally lube up the impeller when you fit it in the housing? if so, what do you use?

Ayuh,... Lot's of Soap works...

And,...
Backflush the In-coming water line, from the drive...
That'll elimate the possibility of a clogged line...

 

[hard-3]

Re: new impeller/housing failed - 99 Mercruiser 7.4mpi bravo 3

backflush the power steering/oil cooler to get out all of those little pieces of impellar that will be plugging the coolant passages . take loose from t-stat housing and give it a good flush with garden hose.

 

[swaldrum]

Re: new impeller/housing failed - 99 Mercruiser 7.4mpi bravo 3

thanks guys. picking up the new impeller kit tomorrow and will retry with it lubed up. Backflushed the hoses today and everything is clear.

scott