It is recommended that a boat impeller be replaced every two to three years or 300 hours, whichever comes first. However, it is suggested to also visually inspect your impeller at the beginning of each season for any signs of wear or damage.

What are the symptoms of a bad impeller?

The symptoms of a bad impeller are your temp will be good at idle but when your increase your speed the temps start to increase.

How long should an impeller last?

Generally speaking a 5 year interval likely works well for most folks. TomP. Mercury recommends changing the impeller every 300 hours...its in the owners manual. It's an easy enough job to do yourself if you have some mechanical skills.