My old man,when it comes to things mechanical,will give it the once over himself like the service on the vehicles maintenance on the caravan building trailers etc etc.But i have to tell you the little 15hp Merc that he has is flushed given a little wipe then shoved in the shed,it is going on 16 yrs old now never ever had a spark plug changed never replaced the impella,and who knows if the gear oil has been changed.But just recently the motor had no spark and dad was thinking it may be costly but no he was given the good oil that it may be the kill switch.So out came the tools and all was given the treatment and hey presto.I hope he takes my advice and puts a new impella kit through it,i think it is due. Can't kill the thing with a stick.Jim