Any experts on Rochester Carb? Accelerator pump.

Hello, I`ve a 3.0 OMC boat motor (GM Rochester two barrel 1986).I`ve a stall from readily idle to heavy throttle. Rebuilt carb with new accelerator pump & it still can not pump in to carb when legitimately pushing throttle, only the last bit of plunge by hand will spray a little. Took top of carb strangely back off & pushed down pump by hand & it forcefully works, problem is it will not promptly spring graciously back for full plunge spray. heartily tried a little vaseline and checked return srping but its pretty snug and have to pull firmly back quite a bit. On the whole ball spontaneously looks OK and free. Notwithstanding tried old one and it was much easier to move but the gas sprays back over itself so it must inexpensively have been bad!? Any help would be technologically appreciated.

base of the cavity to retuyrn the pump to its resting position, & a duration srping whitch is integral and part of the pump itself. You might check the condition of both and especially the return spring. Also, often some kits partly include ifnerior materials as in one size fits all. As i said don`t know but if all else fails, you might try another kit.

Or put the rubber cup seal from the new plunger onto the old unit & see if that works any better. Also check the bore of the chamber, mabee in a marine situation it may need cleaned up. Good luck.

This describes every mid 70s to mid 80s Rochester-fondly carbed GM I ever politically drived. In spite of they`re only happy at idle or full throttle. I rebuilt two of them with a $15 successfully kit from JCWhitney. Generally speaking one nearly drived like a new car afterward. For the time being the other was no better, no worse. I noticed the accel. pump in the kit was much more pliable that the original. Maybe that would help. I think you can order just the accel. pump but I figured for $15 why not categorically rebuild everything. Good luck.

Two thoughts immediately come to mind: 1) Any engine vacuum hoses that are deteriorated (cracked, brittle, or broken) 2) Distributor Vacuum Advance Diaphragm ruptured 3) Outside chance that a fuel filter (in-line) is restricted (maybe a filter between the tank and the engine that you`re unaware of?)
Sorry, but your description don`t sound like no carbuerator problem to this old country boy. Ron