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4.3L V6 OMC
1988 Horizon

in storage since 97, I picked up late last summer.

Looking at it today, running with muffs on in the driveway. I notice rough firing and 3-500 rpm drops. This also plagued us on the few times that we were out late last year.

I noticed air bubbles in the clear fuel line going to the carb.

Normal?

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1988 18' Horizon, 4.3L V6 OMC Cobra
2006 Chevy Suburban to pull it

Nope. You're ingesting air. I'd check the fuel tank and it's pickup for cracks etc. Also check for fuel leaks. Maybe the fuel pump diaphragm is toast.

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1981 Columbia 8.7
2015 Yamaha FZR - 87mph - sold
2006 Yamaha GP1300R - sold
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2000 Four Winns H180 - sold
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Rick's Four Winns H180 Mods/Upgrade Thread

NOT normal, and a sign of a leaking fuel pump diaphragm, this means you need to replace the fuel pump, it's a safety thing on inboards and I/Os so the fuel does not leak in the engine compartment but gets sucked in through this clear line. There should never be gas or bubbles in that line.

And if you didn't last year, get the gas tank cleaned out, get rid of the old gas and if it doesn't already have one, get a water separating fuel filter. I'd take a close look at all the fuel lines, you can lift up the cover over the gas tank to get a good look at em...
Finally, you may have to get the carb rebuilt if it hasn't been in all those years.
The OMC 4.3 is a good running package when set up right but clean gas and a good fuel system check up is in order....

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II