Mercruiser Impeller Questions

[JB25VIP]

I have read quite a few times that an impeller replacement is recommended every two years.

I have a 1997 mercruiser 5.7 alpha 1 outdrive.

My question is what exactly is an impeller and what does it do, as well as where it is located (i'm under the impression it is in the lower unit)

why is it recommended to change frequently?
Is it hard to do? (i'm mechanically inclined and thinking of changing it myself)
I ordered the maintinence manual from mercruiser and i'm hoping it tells me how.

Thanks in advance for any information!

 

[Don S]

Re: Mercruiser Impeller Questions

This is a "In a NutShell" answer and not meant to be a complete discription or explanation.

The impeller is the rubber impeller inside what is called a raw water, or sea water pump. On Alpha I outdirves it's mounted on the top of the lower unit.
It's made out of rubber and has to flex open and closed in order to "Pump" water thru the engine and manifolds to cool the engine. Unlike cars that use air flow over a radiator to cool the engine, there is no air flow. Thus, you need another way of cooling. Tah Dah!!!! Water! That thing all around a boat.

 

[fishmen111]

Re: Mercruiser Impeller Questions

why is it recommended to change frequently?
Is it hard to do? (i'm mechanically inclined and thinking of changing it myself)

Because being made of rubber that flexes to operate inside a stainless steel housing, it wears out over time. Also tends to dry rot (think bike tires) over time from non-use. Normal replacement intervals are 24 months. This small rubber impeller is responsible for the cooling water for the entire engine. No water...fried motor. If you take your time and follow the manual, it is very easy to do.

 

[Bondo]

Re: Mercruiser Impeller Questions

I ordered the maintinence manual from mercruiser and i'm hoping it tells me how.

Ayuh,.... That Sucks,....

We've got links to the Factory Manuals, that are Free.....
The 1s for both your motor,+ drive....

Good Luck,+ Welcome Aboard.....

 

[JB25VIP]

Re: Mercruiser Impeller Questions

thanks everyone for the information, and thanks bondo for the link to the manuals!

 

[turborich]

Re: Mercruiser Impeller Questions

I changed mine a few weeks ago, having never changed an impeller before I thought it was a pretty easy job. You should be able to do it without any problems if you follow the manual.