impeller good or bad
Ding, ding, ding!!! Give that man a cigar. Best sentence on here.
Ya got the thing out already, if you have to ask or its been a few years......just do it. The hard part is done, or, half of it anyway.
Steve's advice on changing them out every 3 years is probably a good idea.
I change out the entire pump assembly every three years on my outboards, and I've never had any problems either with handling the repair or with the motor overheating.
Formerly Steve @ G & S
Is it something I can change myself (fairly mechanically inclined) or do I bite the bullet and haul it to the dealer?
In my case, the dealer I bought the boat from six years ago said they'd replaced the impeller when they took it in on trade, and it performed well up until this spring. When I threw on the earmuffs and fired it up in the driveway this year, the water was trickling out of the tell-tale hole and was too hot to the touch (@ 130 degrees). Since I hadn't addressed the water pump since I bought the boat, I figured, rather than replacing the impeller only, which would run @ $20, I'd be better off getting the whole pump housing kit (@ $75), which included gaskets as well. That way, I knew I'd have a definitive baseline of exactly what was replaced when.
Since this was my first go at pulling a LU, it took me a bit longer than it normally should, but overall, not too tough a fix, and now that it's done, the pump is running well and there's a robust stream of water pumping out of the tell-tale hole.
Do yourself a favor, as these other guys have posted, don't take a chance on damaging the power head by going cheap, in the long run a full kit replacement is insurance against potentially serious damage to the motor.
When you figure the cost of replacing a 20HP motor, the cost of a pump kit is a relative bargain!