Flat Spot at 2100 RPM
Got a customer with a marine 2300. It has a flat spot at 2100 RPM.
The position of the pump arm cam and/or the correct pump cam. He might be using up the total pump discharge to fast.
Low float level. The marine Holley uses an internal Needle & Seat and can only be adjusted with bowl off. The Float should be set to specs held upside down by bending the float tab that touches the needle.
Correct Power Valve (7.5/6.5 hg) They make P/V from 1.5 to10.0 hg.
He should make sure the squirter is working, could be a problem with the inlet and/or discharge check. Turn the engine off, pump the gas while looking down the barrel. You should see 2 good squirts of gas. If not then you have something plugged in the accelerator pump circuit.
Secondarily there could be an accelerator pump problem. It could be it isn’t filling up fully. This would assume that we are throttling up at 2100 RPM. If cruising, then no, it’s something else.
What is flooding? Too much gas is getting into the float bowl. Here are some things to check, not in any order.
- Float is too heavy – Nitrophyl floats are weighed in grams. Brass floats may have gas inside. Shake to listed for gas. If the vehicle has been sitting for months, then the gas might have evaporated. Immerse in hot water and look for bubbles.
- Float is sticking – Check float pin for wear. Is the float rubbing anywhere.
- Needle & Seat leaking – Test the needle & seat by blowing into the fuel inlet and the bowl upside down. You should not be able to blow through. Keep in mind the needle will open with enough force.
- Fuel pump – New fuel pumps are always suspect to have too much pressure. A fuel pump regulator may be in order.
- After sitting for months – The gas may have turned and varnished the inside of the carburetor. You would probably smell varnish. Clean the carburetor, gas tank and fuel lines. Note: Simply replacing the gas will work until the varnish falls off the inside of the tank.