Mariner 115 horsepower

[Digger1264]

I have a 1989 Mariner 4 cylinder engine have done a lot of replacing of Parts but can only get 35 miles per hour out of motor it used to do 48 on a 19 89 Alumacraft 170 tournament Pro boat I'm stumped I don't wish to replace a whole lot of electronics I believe is a number 4 cylinder or bottom cylinder carburetor issue can anybody help with this issue thank you

 

[johnnygjr]

Is motor on the same boat that used to do 48mph, Serial # please? Different weight boat? Hull type? What your WOT, top rpms? Do a cylinder drop test, Pull 1 ignition wire at a time to see if rpms drop,Troubleshooting 101,compression test first, spark test second ,fuel diagnostics third!!!