48 spl still surging

I opened the fuel pump and found that the lower rubber check valve was in pieces and thought that surely was my problem. I bought and installed a new fuel pump. I the problem is still there. I can not believe there was no change do to the condition of the fuel pump. I checked all the connections, changed tanks and hoses, disassembled and cleaned the carbs. The engine starts and runs great until I go to WOT, after 100yrds or so it falls flat and starts surging. I can push the key priming pump and it will try to run right. It is as if it is running on one cyl. Do the check valves each supply a carb or both? If each which valve supplies which carb. I think part of the destroyed valve my be stuck somewhere in s carb.

Re: 48 spl still surging

First I would eliminate the ignition system by using an inductive timing light to make sure I was not dropping a cylinder. If you are not loosing spark, use a spray bottle with fuel mixture in it and spray in each carb and see which one picks up. That is the carb giving you problems. When you cleaned the carbs, did you remove the high speed orifices and make sure they were clean?

Re: 48 spl still surging

Pushing the key adds fuel via the primer so if the engine then picks up (or attempts to) then fuel delivery is still the problem. Fuel pickup in the tank, anti-siphon valve if there is one (on the outlet of the tank), bad primer bulb, fuel line failing internally, restriction in the carb(s), or incorrect fuel pump.

Re: 48 spl still surging

I like that idea with the spray bottle. No I didn't remove the orifices. I am going to tear the carbs down again today. Putting the boat in the river is a problem for now. There was a big fish kill (pearl river louisiana) and they shut the river down. 45 miles of dead fish.
Thanks

Re: 48 spl still surging

The fuel pump is identical to the one I removed and I bought the motor new. I am going throught the fuel system and carbs again today. I have four different tanks and hoses. It does the same thing with any of the tanks and hoses. The problem started 3 years ago with it just bogging down a little for a short time after running for 5 mins or so. After it sraightened up it didn't act up the rest of the trip. Last year the bogging kept getting worst. This year the surging started.
Thanks, with you guys knowledge I saves a lot of guess work for a lot of forks!