Sputter & Kicking Help....

[ski4funn]

I have a '77 240 SVX240 with a GM 350. The engine was rebuilt about 1.5 years ago and the carb. was also replaced with a new 4 barrel. The boat has run fine in the past until several month until I took it out on the bay. There was probably 3' swales when we launched and towards the end of the day when traveling back to shore at almost WOT (the sea swales had died down), the boat started acting like it was starving for fuel, sputtering and idling erratic. I slowed the boat down about 1/4 throttle for about 5 minutes and went back to WOT. It lasted about 2 minutes and it started acting up again. I changed the fuel filter, and added 2 can's of Sea Foam (70 gallon fuel tank). On the next adventure to sea a few weeks later, the boat ran much better, acting up just a little towards the end of the day, but nothing like the prior event.
I just go back off the lake today and the same thing. I have had the boat out 3 times this year without any problems. After running the boat about 30-45 minutes it started acting up. I returned to shore, replaced the fuel filter and went out again. The boat ran fine for about 5 minutes and acted up. It seems when the boat engine warms up, it starts acting up. Any ideas would be of great help....​

 

[Tail Chaser 661]

Maybe vapor lock :huh:

Ive heard having a steel fuel line from the mechanical fuel pump to the carb can cause vapor lock.

Maybe the fuel pump is weak, not pumping enough fuel at WOT.

Maybe fuel line from tank to carb/filter etc is old/cracked.
That may cause fuel pump to pull air cutting some of the fuel flow to the carb.

 

[fc3]

Sounds like fuel problems. Either a dirty fuel filter, yes again, dirty anti-syphon valve, bad fuel pump or a dirty or maladjusted carb.

You might have two fuel filters, including one in the carb inlet. Check again.

Best regards,
Frank