Re: mercury 500 thunderbolt 50 hp timing problem
It's usually something like poor compression or a fuel delivery issue.
Sometimes it can be ignition (even timing), but from seeing all the post that come by, I'd guess mostly fuel.
Run a compression check to make sure you have a solid foundation on which to perform repairs.
See, that if by squeezing the primer ball in the gas line while operating the performance immediately improves.
Look to see if gasoline dribbles out of one or more carbs.
Run those diagnostics and get back to us.
Of course, if by chance you, or someone has somehow messed the timing up I guess It could certainly be a timing issue.