My 15 year old yamaha 25hp 4 stroke was running cruddy. I took it into the shop and got the bad news today. $450.00 if I want it to fix so it will run good. $275.00 IT may idle ruff when their dunn. $1900.00 for a total rebuild. They say it is noisy and that the crank and bearings are probably starting to go out. I have had great luck with this engine at has over 1500 hours on it. Some of them pretty hard. I cant make up my mind buy new or fix the thing. It aint worth rebuilding. But it is a roll of dice how long it will last if I have them fix it.