Impeller pump change warranted? Yanmar 3ym30

[jbinbi]

New boat purchased last spring. Put 45 hours on the engine. Changed the oil in the fall.

Should I be changing the raw water impeller now or can I go another season on it? Also, I have a spare impeller from 5 years ago (was boatless for 4 years), is this OK, or do they degrade just by existing (kept stored in original bag).

[SailingHarmonie]

Sitting in the box, on a dark shelf degradation will be minimal. In an engine, without turning, the blades take a “set” and become more fragile and less efficient.

Just change it as a routine each season. These are not expensive. The damage from an overheating engine can be VERY expensive.

[Avionics_Joe]

Change the lip seal when you change the impeller, if salt water gets on the bearings it's all over. Don't get them from Yanmar, can be had cheap on Amazon.

[FlyingScot]

Change yearly so you never worry about having to dig out the broken bits from the heat exchanger.

Leakage past the lip seal is another issue mentioned. The shaft will get a wear spot on it eventually preventing even a new seal from working.

Replacement of the whole pump assembly can be a worthwhile choice if you replace with better seal design (mechanical vs. lip).

[Dockhead]

I'm going to be a bit contrarian here and say that not all impellers need changing every year.

It depends on the pump and depends very much on the installation -- does your impeller run dry for a moment to prime itself? Or is it below the water line and always immersed in seawater? Makes a huge difference to impeller life.

I change mine every 2 or 3 years or 500 hours or so, and the impeller always looks like new. Never seen as much as a crack in one of them. Yanmar says change them every 1000 hours. I always buy the Yanmar ones despite the availability of cheaper generics, because they are threaded for the ingenious Yanmar impeller puller, which is really essential for the hard-to-reach backwards-mounted pump on the 4JH3 engines.

I have something over 4000 hours on my Yanmar 4JH3 HTE main engine and will probably swap out the entire pump next year rather than change the impeller. I have been carrying a complete new spare seawater pump for years; might as well put it to use.

I've worn out two pump covers during my ownership of this boat (which started at 800 hours or something on the main engine). I replaced a worn out Speed Seal cover last year (with an original Yanmar one since Speed Seal is no longer available).

Now my generator is ABOVE the water line, and its seawater pump lives a much harder life, as it has to run dry for a moment to prime itself. I change that impeller every year. I've burned up a few impellers over the years by forgetting to open the seacock before starting