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hp 500 carb runs great then falls off shortly after

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hp 500 carb runs great then falls off shortly after

Old 07-25-2013, 06:32 PM
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Default hp 500 carb runs great then falls off shortly after

Im stumped. The boat was running great, and after a weekend on the lake has progressively gotten worse. I thought it was a filter so i changed that, then the fuel pump. Still no go. Itll turn 5k out of the hole and lean out and fall off. If you pop it in neutral itll idle but any throttle it will die. Few seconds to recover and itll run fine til you mash it and itll gradually fall off again. Carb?
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Old 07-25-2013, 08:49 PM
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Here's just an idea, what about the tank vent, I know down here mud daubers plug everything up!!
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Old 07-25-2013, 09:13 PM
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bad coil? ground?
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Old 07-25-2013, 09:57 PM
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check the float leval with the boat in the water.
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Old 07-26-2013, 06:24 AM
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Originally Posted by CAPTAIN JACK
Here's just an idea, what about the tank vent, I know down here mud daubers plug everything up!!
Took the fill cap out just to be sure. Only thigh that sticks out in my mind is the cam lobe the pump rides on.
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Old 07-26-2013, 06:46 AM
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Have you checked fuel pressure? Don't you have hp500's? Fuel pump on the sea pump?
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Old 07-26-2013, 11:56 AM
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Check the pick up tube in the fuel tank.
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Old 07-26-2013, 12:11 PM
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Put a fuel pressure gauge on it. If it ran fine on the lake last weekend, sounds like something is going on. The fuel psi gauge will tell you something.

I recently took a set of carbs apart for a guy, and there was a bunch of $hitty goo in the fuel bowls. I thought I recall you having some issues clogging fuel filters? Hopefully you don't have something stuck in the pickup or lines. Or even a cracked pickup tube sucking air. (the lake can be rough and do things like that).

Before anything i'd throw a gauge on it.
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Old 07-26-2013, 08:43 PM
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They have gauges on them. 6.5ish at idle, rock steady at 5 psi throughout all ranges. Next step is carb i guess. There any screens in the carb i should check? Going to change the coil first just out of curiousity. It runs great the first few minutes on plane before the engine compartment gets heat soaked.
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Old 07-28-2013, 09:42 AM
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Turn out the barrel filters in the bowls were packed with a sticky white sand like substance. Blew them out with brake clean and runs like a top. Thanks for all the opinions!
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