Hello again. To refresh your memories, I have a 22' proline walk powered by 200 hp carbed merc. Motor runs very well-most of the time. Doesn't smoke, burns 9.5 gals/hour @4000rpm(flow meter). I do alot of fluke and bass fishing on LI sound. Here is the problem. After drifting, usually after three or four hours of fishing, when I throttle up the motor bogs down and occasionally stalls. It will only act like this 5 or 6 time a day. If you push the choke in the motor responds well. Over the last three years this what I have done. New fuel line from filter to the motor, new primer bulb, new fuel pump, rebuilt carbs, new anti siphon valve, new 10 micron water/fuel filter, new fuel lines on engine(carbs etc.), been using seafoam, star-tron and marvel mystery oil (at times),use sta-bil every fill up, flush engine every use with salt-away. new thermostats, new water pump, new plugs every spring, and use full synthetic pennzoil 2 stroke oil. I have adjusted the screws on the carbs every way possible (rich, lean etc). One other note, the engine starts flawlessly all the time and idles perfectly. I get full listed RPM and smooth cruise speed. The only constant that I can put my finger on is that it takes 3 or 4 hours of fishing for this bogging down to start happening. Maybe something is heating up? I have been fighting this for three years now. Any and all suggestions will be appreciated. I understand the safety issues around removing the anti-siphon valve, but am considering replacing it with a plain hose barb! Again, thanks.
