Carb replacement question

Ok, I've got a 1975 Mark Twain powerd by a Mercruser 888 (ford 302). Pre alpha drive. I have the engine out and and have problems wth the carb. The engine had sat for maby 8 years when I bought it and now it runs great (at times). I cleaned the thick gunk out of the carb and installed a renew kit and I can't get the adjustments right for it to run prpoperly. Its like its pumping way to much fuel w/no air. turning idle mixture screws have no effect whatsoever. If I shut the fuel off it runs great for an instant before the fuel runs out. I also have a concern about the carb itself. It is a Holley model 2300, 300 cfm (list number 6317). It doesn't have the "J" tube like the current marine carbs and I think I should just go ahead and replace it.

The question is should I send the carb out to be rebuilt by a pro or just replace it?

If I replace it would a 500 cfm 0r 600cfm 4 bbl be to much for this motor? The price of the new or refurbished 2bbl's are way higher than some 4bb's i have found.

Re: Carb replacement question

Ayuh,...... If it were Me,......

I'd find a 4bbl. Manifold,+ drop on an Marine Edlebrock Preformer, 600cfm Carb.....

Re: Carb replacement question

Ditto on that.... maybe add the edelbrock performer manifold to with model 1409 carb...

Re: Carb replacement question

I think a 600 holley will not be optimal, too much cfm, and unless you know how to tune a holley.
Major pain in the butt.

Re: Carb replacement question

Sorry I wasn't clearer... I think both of us were talking about an Edelbrock performer 600 cfm (marine) carb model number 1409. That's just about perfect for a 302 and would probably work great right out of the box with little or no tuning. They're also easy to tune. can get a new one for a litle over 300. There is a corresponding (number 2121?) edelbrock performer aluminum intake that would work very well with it for 160... can get from any of the big parts houses like summit, etc...

Hope this is helpful

Re: Carb replacement question

if your turning the screws and nothing is happening you either have an air leak on the intake/carb base/carb throttle shaft, a fuel leak inside the carb (like a leaking accelerator circuit), or your timing is incorrect.

Re: Carb replacement question

Thanks for the input, I was leaning towards the 500 cause i thought the 600 may be too much, ill check around for the manifold and try to decide between the 500 or 600.

Captjason, I think you nailed the diagnosis. I'v been try to get the timing set but without getting the engine to idle correctly its impossible. I think there is a major fuel leak in the carb and a vacume leak. The carb and fuel system in general was in pretty bad shape when i started.

Re: Carb replacement question

I've got a 600 cfm Edelbrock with a performer intake on my 4.3 v-6 and it works great. Would imagine that you can look at the jetting required for that set-up and the stock supplied jet and rod combo for a stock 350 (drop on from edelbrock), move about 3/4 of the way from the 350 mark to the 4.3 point on edelbrocks handy little jetting charts and get a good guess on where to start jetting. Might hit it right on the head the first time. You would probably gain a little horsepower in the process and not have to worry about rebuilding the old set-up. For the 500 bucks it would cost to do the new carb and intake, I know how I would rather spend my time. I also know that money is tight for a lot of us these days... Either way, good luck with it.