replace all Yamaha carbs Chapter 2

[seamanship]

Re: replace all Yamaha carbs Chapter 2

Guys, some of you are familar with my first post "replace all carbs" last week.
I now have the boat back after paying $275 restocking fee for the carbs, which they still didn't have one of.
Mad as hell but not worth a fight.
I have been through the carbs and they are as clean as can possibly be. I even ran the fluid test thru the inlet line and the flow from all 6 jets is as consistent and straight as it could be. I tried high pressure and very low pressure and flow is great. No stop, starts and no erractic movements in stream.
100% confident the carbs are good. But I really need help finding root cause.
I put 2 new fuel pumps on it when this all started and didn't help.
Could I possibly have gotten a bad one from Yamaha?
How can I test it ?
How can I find a vacuum leak in the fuel system ?
Can a prime bulb be the problem ? Maybe restricting the flow?
I have taken the fuel line out of the tank and intake and filter are clean.
Again it starts easy, runs smooth but will only turn 4800 RPM and use to run 5800.
I REALLY appreciate you fellows helping me solve this. Been without a boat since Sep. and the fish are biting here.
Thanks,

I was using corngas in my Yamaha F40TLRY this completely ruined the carbs and other parts of this engine. I completely overhauled the carbs, new timing belt, and value adjustment. I thought I was set. The engine idled good and ran fine at sppeds up to1800 and faster speeds of 2800 to 5000. Would not run at 1800 to 2800.
I checked everything again and again and could not fine anything wrong. I then started to use a vacuum guage on my intake and seen I had a serious fluctuation. I THEN DID A CYL PRESSURE TEST AND FOUND I HAD 83PSI IN ALL THREE CYLS. HEADGASKET. NEVER CORN GAS AGAIN. DID YOU DO A CYL PRESSURE TEST?

Just a little history and suggestion.