02 15HP 4-Stroke high rpm sputter

[Warp6]

Just got this 15hp Yamaha for my 14' jon. It's super clean, starts idles and runs great. Problem is, at about 80 percent throttle it sputters and won't fully rev. The more I twist the throttle the faster the sputter. It sounds more like a carb adjustment issue and not so much ignition related. I don't see much on the carb to adjust but then again, I've never owned a 4-stroke outboard. I put a new set of plugs in and it didn't have any effect. Also, I'm running fresh fuel. Before I start wrenching I figured I better ask for recommendations. Thanks in advance, Craig

 

[99yam40]

Re: 02 15HP 4-Stroke high rpm sputter

Sounds like a fuel issue.
Could be a plugged jet, trash or water in bowl, fuel pump, or sucking air into fuel pump.

Pull the carb and inspect and clean, test pump pressure and vacuum, and use a clear piece of tubing to check to see it there is air getting into the system.

Look under the frequent asked questions heading for testing fuel system for more info.