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Matt, Engineer
Category: Car
Satisfied Customers: 20377
Experience:  Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.
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start to run rough and bog down, rpms fine

Resolved Question:

i have a 454ci engine in my boat, 4 barrell carb, when i run it up to about 3000rpm it will run smooth as silk then it will start to run rough and bog down, rpms fall, then almost stall out unless i pump the throtle a bit - i can keep it running and then it will smooth out and run fine again. Then it will do it all over again! would you think possibly a carb issue? this is when the boat is in neutral, havnt had it away from the dock in a while.
Submitted: 5 years ago.
Category: Car
Expert:  Matt replied 5 years ago.

I'd suggest removing the carb and stripping it down and giving it a good clean and its quite possible one of the air passages is blocked with dirt

also check that the float height inside the carb is correct, as if its set too low then you'll run out of fuel when trying to accelerate
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