Re: [OMC-Boats] She let me down...

From: Justin DeSantis <duc1098desmo@...>
Date: Fri, 18 Sep 2009 22:15:27 -0400


Where are you hooking up your vacuum gauge? On bikes there's always a
nipple on the intake manifold. I don't see any on my old Buick motor.
Thanks for all the help BTW. I'll start a new thread to share the
results of the carb rebuild.

On Fri, Sep 18, 2009 at 12:08 PM, BC Howk <bchowk@...> wrote:
> Justin,
> I've been saying this on the list a bunch lately, here is a link with some
> detail on the tune up procedure I use...
> I like the vacuum guage procedure because you can tune your engine "BY THE
> NUMBERS" no room for subjectivity...
> the link will back me up on this, get it running and warm, check your
> timing, get the idle speed (on the port side) in the ball park, adjust your
> port mixture screw in till it stumbles then out untill you peak the vacuum.
> adjust your starboard mixture screw in till it stumbles then out to peak
> vacuum...repeat...timing, idle speed, mixture (peak vacuum) untill you can
> get no further improvement.....BY THE NUMBERS you are looking for timing 5
> degrees BTC (at idle), idle =550 RPM, maximum vacuum possible with the
> timing and RPM dead on (vacuum reading will vary by engine but guessing you
> should be in the 20 PSI territory)
> The only difference you may have from this car tune up proceedure is that I
> don't believe you have a vacuum advance on your distributor (a little cone
> with a vacuum hose that goes to a vacuum port on the carb)...So you will be
> able to ignore the golf tee part,
> SIDE NOTE: When you get your manual it will talk about the mechanical
> advance but basically the advance curve is controlled by weights and springs
> inside the distributor and are pretty light compared to "normal" automotive
> applications. Boaters aren't starting and stopping or changing gears so if
> you throw the throttle down we want to get the timing advance in pretty
> quickly to get us up to max power to tow that skier and once we get up to
> speed we stay there for a while...
> hope this is helpful.
> Cheers,
> B.C.
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Received on Friday, 18 September 2009

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