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Motor surging above 3200 rpms

Old 06-15-2005, 08:30 PM
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Default Motor surging above 3200 rpms

I have had a problem recently of my starboard motor surging at around 3200 rpms. This only happens under load (when I am running the boat).The boat will refuse to go past 3200-3500rpms. When the boat is in neutral it revs to 6200 rpms without a hiccup.
The engine in a 350 small block with mercury racing 700cfm carb.
So far I have checked distributor, replaced coil, rebuilt carb, checked fuel pressure from fuel pump..all this to no avail.

Any help appreciated as I running out of possibilities.
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Old 06-15-2005, 09:08 PM
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Default Re: Motor surging above 3200 rpms

Sounds like a mixture problem to me. It's proably running fat or the engine would be backfiring.
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Old 06-15-2005, 10:46 PM
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Default Re: Motor surging above 3200 rpms

Does your carb have the inline filter near the fitting from the fuesl line to the carb? I had an old donzi that did what you describe and my filters were plugged.
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Old 06-16-2005, 06:47 AM
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Default Re: Motor surging above 3200 rpms

could be air entering your fuel line or begining form of vapor lock
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Old 06-20-2005, 01:04 AM
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Default Re: Motor surging above 3200 rpms

Ttt
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Old 06-20-2005, 10:35 AM
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Default Re: Motor surging above 3200 rpms

Swap Carbs between motors & see if problem moves to other motor.
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Old 06-20-2005, 12:11 PM
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Default Re: Motor surging above 3200 rpms

I had a similar problem last year. Turned out my anti-siphon valve in the tank was bad. Hook up a portable tank to the fuel pump inlet. If problem goes away, that's probably the culprit.
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