I think I have heard you should change a water pump on a outboard ( 40 HP ) once a year. Mine has not been changed for three years yet pumps a good stream from the motor head and there is no overheating. Should I go by the stream it pumps or some time or usage measure?

Age, go by age, Most impellers 3 years at the most. Heavy usage like saltwater, 2 years. Small Merc, yearly, small J/E 2 years. Your 40hp , at the most 3 years.

no doubt plenty of impellers out there been in service for many many years and haven't failed yet, but you know the downside.

I try to do mine every 2 years on schedule -- couple times I've waited till I noticed the pee stream has got weaker, seems like it happens during the third year.

i do it every one and a half to two years... like jtexas said - you know the downside

Impeller replacement also depends on how often the motor is run...A more active engine will keep the impeller in good condition than one that's used only during the summer months...The rubber will dry out faster, causing fins on the impeller to break sooner and require replacement before an engine that is run every week...That being said, 2 years max for the outboard engine and 1 year on my inboard engines...I don't care to risk damaging the engine...

I look at the condition of the impeller that came out to assess how long I can go. 3-4 years for me. Different for everybody.

I've got a '83 Evinrude 115hp...never had the lower unit off. Do you think it's about time? I've always been told to listen for the warning buzzer. I have gotten to where I change the fluid about every 3 years though.

Every two years. It is cheap insurance!

its the cheapest insurance you will ever invest in!! i am having mine done this week. i want mine done every year.... i fish in some shallow water and I can just imagine what the sand and silt does in that rubber/metal configuration(think: sand paper)....

I change the impeller once a year and every other year I replace the housing. I just sleep better doing this.

I have a friend with a 1991 Tracker, 40hp Evinrude. He bought the boat new and has never changed the impeller. My 1968 33hp I have to change every 2-3 years and usually have to change the impeller housing a base plate as well.

On my 175 merc I like to change the impeller every 2 years and the housing every 6. Gear oil I change every year just to be sure there is no water in there.

tommys right every other year, cheaper than a new powerhead

ya i would change it. better safe than sorry. good luck

when you hear the buzzer, shut 'er down LIKE RIGHT NOW before she seizes.

I just pulled the impeller from a 6hp 'rude, my dad bought it new in 1973, never had the water pump serviced. Hasn't run since maybe 1985. Honestly it doesn't look all that bad......