Yamaha 250 won't pass 4300 RPM.

[JrMako]

Hello everyone. So recently father and I purchased a 26 Mako with a yammy V76 250 hanging off the back of it. On its first trip it wouldn't pass 4000rpm so that week I replaced the fuel from tank to motor including primer bulb, 2nd trip still same, replaced plugs and did a power tune through the carbs and tightened all the carb linkage ( linkage was all lose) checked compression and all cylinders are at 120, 3rd trip now I'm at 4600rpm at WOT. Also primer bulb won't hold prime for more than 2 to 3 min but it does get solid when primed. Motor starts and idles great and I can run 4600rpm all day with no hiccups. Any ideas on what can be holding me back from 5500 rpm???? Prop is a Stilleto 14 1/4 X 17. Went to start it yesturday and it took forever, along with some black gunk coming out of the exhaust, could it be a leaking fuel pump??

 

[BaileysBoat]

Lots of boat for 250 hp. Sounds over propped. Primer bulb not a problem as described.

 

[99yam40]

Now you have gotten basically the same info from more that one web site,

Yamaha does make a test prop to test motors to see if they can spin it up to a certain RPM while sitting still
You would be ahead of the game to find a shop that has one for your motor and test your motor.
that way you can know if the motor is a problem or not,.

So you can start work on the proper problem,
wrong prop, not rigged properly, hull problem , Motor problem, or too little HP,