Mercruiser 7.4L impeller failure

[Air O'Nautical]

Now I'm the first to harp about proper maintenance on a schedule instead of waiting for a failure.
This one was in its 3rd year of operation.

 

[scoflaw]

Did 1 of my engines last year with a 4 year old impeller 400 hours, looked fine with a set. No difference in water pressure or temp with the new impeller. Did my other engine the previous year and it looked so good that's why I waited till year 4 for this engine.

 

[Air O'Nautical]

This was a Sierra part....I replaced it with a OEM pump.
Hate to admit it's MY boat!

 

[Skuza]

I just did ours a few weeks ago and they were about 3.5 years and prob 20ish hrs a season. Looked brand new with only one minor crack at the base of one of the blades. I too am funny about using oem when possible.
One thing I notice on yours is the wear on the tips of the blades. I have to check ours. This looks like something that would happen from dry running? Or do you spend a lot of time in the shallows stirring up the bottom? Maybe insufficient water flow too? Dirty strainers/intakes? Kinked hose?
I agree about staying ahead of the curve. Changing the impellors is fun enough let alone chasing the pieces out of the system.

 

[Air O'Nautical]

It's a surprise to me as it's my first one to come apart
There are very few hours on it too but, I believe the clock starts when it's installed ... not the hours it's run.

I often work on other boats and It's common to see, usually after more than three years tho..

My boats always in at least 6ft of water but, can't discount the possible unlikely encounter with a plastic bag or ? temporally restricting flow.
The intake hose is 3years new and has no kinks.
The strainer is clean.

Runs fine after the replacement.

 

[dpmulvey]

Impellor should be a two year replacement or an annual replacement depending on use. Merc makes it a VLPITA to perform routine maintenance every chance they get.

 

[Boater420]

Once a year.

 

[northern]

Has anyone else had problems with Sierra parts. I had a distributor cap that fit very tight. The engine had no power. I tapped it down into place and it worked fine. I also got two impellers from Sierra they seem softer than the OEM ones.

 

[BillK2632]

Has anyone else had problems with Sierra parts. I had a distributor cap that fit very tight. The engine had no power. I tapped it down into place and it worked fine. I also got two impellers from Sierra they seem softer than the OEM ones.

I've used a lot of Sierra parts over the years - water pump impellers, bellows, shift cable, trim senders, filters, dist cap/rotor. Never had a problem, I have found that the OEM fit on some parts is a little better (Sierra bellows were a tighter fit than OEM), but never had a situation where a Sierra part flat out would not work or failed prematurely.