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  1. #1

    Default '48 Ventnor 18 Gray Marine flat six fireball 150, dual Zenith updraft carbs

    Hi All,
    So I have an old Ventnor barn find I picked up last year. It appears to have not been in the water in 40 years judging by what I found and the condition of the belt, hoses, clamps, etc, all being very old technology.
    It's a 6 volt positive ground electrical system, with dual Zenith carbs, updraft intake manifolds.
    When I got it the floats were so far out of adjustment on the carbs that fuel couldn't enter the bowls. I rebuilt both carbs, set the floats, replaced the head gasket, the cylinder walls and valve-train are in great shape, very little wear.
    The valves are set to spec. I also rebuilt the starter, new brushes, bushings, cleaned, it has a 6 volt electrical fuel pump, with an integral filter which I cleaned and also replaced the inline fuel filter.
    I cleaned the air filters for both carbs, replaced the battery and cleaned all the terminals, wiring etc.
    I replaced the head gasket with David Vaness' copper gasket and torqued. New plugs, checked the points, cap, wires, rotor and had to weld new teeth on the flywheel with my TIG welder and filed them up to get the starter to engage.
    I've had it on the water a few times, and this last week I made final adjustments to the carb jets, idle and main, also the ignition timing. All in all it runs great, starts up and idles at first push of the button, but I cant get the engine to speed over 3000 rpm and it only goes about 25 mph, the Ventnor literature states that this model with the fireball six 150 should go 42 mph. I've also checked and adjusted the linkages for the carbs and I'm certainly getting full WOT on both. The prop is also in good shape. Does anyone know the maximum rpm for that engine and what am I missing to get more out of it?

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  2. #2
    Join Date
    Sep 2008
    Maryland - USA

    Default Re: '48 Ventnor 18 Gray Marine flat six fireball 150, dual Zenith updraft carbs

    Welcome to ME.com!

    As far as the specs go, you might try over at oldmarineengine.com...more interest in that vintage there.

    As far as limiting out at 3000 rpm, it sounds like you touched on everything but timing advance...lack of timing advance will limit the engine's power output as well as rpm...

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