Stern Drive Impeller

[capecodder116]

I have a 1984, 22 foot Tiara Continential with a mercriuser 260 engine, closed cooling system, Alpha 1 sterndrive....my question is, is it necessary to replace the impeller in the sterndrive as my engine cooling system is a closed system? Can I remove the impeller completely or does it circulate water thru the drive as well?

 

[zzzzz]

Re: Stern Drive Impeller

it provides cooling water to the exhaust... don't take it out unless you would like to cook on your manifolds !

 

[tommays]

Re: Stern Drive Impeller

The pump supplys water to cool the heat exchanger like air would cool a car radiator


you will overheat pretty quick if it is not in good condition



Tommays

 

[John Liss]

Re: Stern Drive Impeller

It is also a good idea to replace the impeller every two seasons. A $10-$30 part can save you about $5000 for a new engine.

 

[capecodder116]

Re: Stern Drive Impeller

Thanks....I do replace every two years...wasn't aware it cools exhaust gases....but It is caped off inside the boat so I don' think it has anything to do with cooling the heat exchanger as the raw water pump circulates water thru the exchanger.....Thanks for the replies.

 

[Don S]

Re: Stern Drive Impeller

You aren't giving us all the information.
If the drive cooling is capped off inside the boat, then you MUST have an engine driven raw water pump to replace it. This was done on engines that has engine coolant (antifreeze) in the exhaust manifolds along with the engine. The pump in the drive wasn't big enough to handle the extra heat, so the engine mounted pump was used.
The engine mounted pump also has a rubber impeller, and should be replaced every other year. The one in the drive should be left in, as it does help cool the outdrive as water goes thru the upper gear housing while it's running.

 

[capecodder116]

Re: Stern Drive Impeller

Yes, it does have an external raw water pump driven by the engine...and I do replace the both stern and external impellers every two years. I was just curious to know if the stern would still be necessary....thanks to all....

 

[zzzzz]

Re: Stern Drive Impeller

if it is capped off then it does nothing and should not be needed...there is no water circulation internally in the drive

 

[Don S]

Re: Stern Drive Impeller

The hose is supposed to be cut off just in front of the bellhousing. This will allow water to move thru the water passages for some cooling before leaving the hose.
The transom shield HAS to be blocked off, or water could come in the boat.