More on Water Pump Impellers

[johnmurray]

Following the advice provided from this list as well as that of my local Yanmar dealer I decided to have the engine cooling water pump impeller changed at the 400 hour mark. (My engine is the Yanmar 315.)
The work was done by a local licenced mechanic who is very familiar with marine diesel engines. While he was ultimately successful, he said that it was the most difficult impeller change he had ever done because access was almost impossible and there was virtually no clearance after the pump cover plate was removed to enable extraction of the old impeller and insertion of the new one. It would be impossible to do this if there was an impeller failure while underway.
Are we missing something? Is there a secret to this?
By the way, the old impeller looked brand new, and I noted that the operating manual suggest an impeller change at the 2000 hour mark!

[Dave39]

If you'll scroll down this section to Feb. 2008, you'll see my question regarding the same. The only response I got was sufficient for me to do the job myself, though it took more than a few hours. By removing the entire pump assembly, life gets easier. And like you, I noted the 2000 hr. recommended period, but figured that was for on road vehicles that didn't sit for 6 or 7 months unused and finding a "set". I now have a perfectly new appearing impeller for a spare, and I hope to God I never have to change one again.

[fairtide]

Do on-road engines have impellers? With no raw water to suck up for cooling the chemical coolant mix, there probably is no impeller at all.

[RobS]

Are we missing something? Is there a secret to this?

I am very surprised that he did the impeller change with the pump in place? Two nuts and hoses clamps and the pump slides right off the studs and is in your hand in 5 minutes. This photo shows just how tight it is in place.