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Discussion Starter #1
So i've got a '73 jet boat with an olds 455 on it.. time for a new carb. looking for suggestions!! i tried a (brand new) edelbrock 750 on it and it ran crappy for some reason.. also tried an old holly and it ran OK, except the carb turned out to be a piece of junk (was flooding out, sinking float too i think)
 

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My experience with carbs is that they need to be set up and adjusted for each particular application- set the venturis, float, main and idle jets, to suit it's use. You can't just slap a new carb on and expect to fix your issue. Any carb would do well if set up properly. Start with the basics.
 

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Discussion Starter #6
The edelbrock was new, the holly wasn't.

that demon carb looks a bit overkill. i was thinking something in the 750cfm range.

i've got a quadrajet on it right now, runs horrible (has issues with the secondaries sticking and dumping too much fuel too. among other things like idle problems)

i'm not a carb expect.. i don't really know how to tune the carb for the application.. since it's on a boat every time i screw with it some, i think it's running fine (sounds fine under free revs at home) but then when it's in the water and the engine has a load it's another story again. it's not like tuning a car/truck where i can test drive it, tune it some, try it again, etc.. I have to mess with it.. then take it an hour and a half to the lake, then it doesn't run good. (yes, i have tuned it some while on the water, today for instance i tried adjusting the timing while someone else was driving it full throttle) but it seems to come back to the carb sucking.
 

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The edelbrock was new, the holly wasn't.

that demon carb looks a bit overkill. i was thinking something in the 750cfm range.

i've got a quadrajet on it right now, runs horrible (has issues with the secondaries sticking and dumping too much fuel too. among other things like idle problems)

i'm not a carb expect.. i don't really know how to tune the carb for the application.. since it's on a boat every time i screw with it some, i think it's running fine (sounds fine under free revs at home) but then when it's in the water and the engine has a load it's another story again. it's not like tuning a car/truck where i can test drive it, tune it some, try it again, etc.. I have to mess with it.. then take it an hour and a half to the lake, then it doesn't run good. (yes, i have tuned it some while on the water, today for instance i tried adjusting the timing while someone else was driving it full throttle) but it seems to come back to the carb sucking.
ive got a 351 windsor with a 2bbl holly on my boat, and float level adjustment is critical due to severe angles when trying to get on plain. you have to have plenty of fuel during takeoff or it will starve for fuel in a few seconds after hammering on it.:beer
 

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Discussion Starter #8
So i'm thinking about a holly... but my experience with them is that the F-ing vac secondaries never open (how can it? there is no vacuum at full throttle) any opinions?
 

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I'm no carb expert either, but in dialing in carbs on a car, you gotta tune it under a load or on a dyno. With cars, you can often find someone with a similar setup and get a baseline to tune from. The same applies here, but I don't think you'll find someone with a similar setup in a boat.

Maybe try some plug chops- run it wide open on the lake, then kill it, pull the plugs to see, if it's rich- black plugs, lean- tan plugs, etc... Wish I could help ya better.

Edit- You'd spend better $$ paying someone to dial in the carb you have versus buying new carbs to throw at it.
 

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i used to have a 455 punched .30 over, balanced and blue printed. it (18 ft jet boat) ran like a bat out of hell with a holly 850.
 

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motorcraft 2150
 

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LS Swap Everything!
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that demon carb looks a bit overkill.

Overkill shmoserkill do it!
:toothless

**Edit**

We ran one on a 350 ci chevy in an orig v6 camaro. We had a little elbow hat on the carb going down into ducting/piping for a "CAI". Had shortie headers, and an edelbrock manifold with a slightly more than mild cam. Car ran like a raped ape.
 

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Discussion Starter #15
Mechanical secondary Holly


too expensive. they start at like $360.

i think i'm gonna try the carb off my scout on the boat.. and see what happens (edelbrock 750) if i can get that carb to work well with the boat i'll be happy. then i'll just buy the $199 e-brock 600 to replace it with :thumbup
 

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I would think any of the carbs you've tried allready would work just fine. Assuming they are in good shape and adjusted properly :shrug
 

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You know who does carbs right ?.. Bigs. I had a custom built 750 Holley done for my 351c, He told me that I wouldn't need to keep my foot in it when the engine was cold to get it to idle EVEN with the cam I was runnin', He was right. I got a ton of power out of my 351c and it was a straight bolt-on ! I believe they are on Ebay too.
 

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That quadraturd should do just fine, how about you throw it on your scout and make sure the carb is the prob.... before you put the edel' 750 on it and take it to the lake again
 

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well, it sounds like you are trying to do this on the cheap, but holley makes boat specific carbs as well as the truck avengers for things that run at angles or get shaken around alot. something must be up with the carbs you have. i've always heard good stuff about quadrajets and angles/shaking. i had a edelbrock 750 on an old 460 that would run pretty flawless on most angles, and i beat the shit out of that truck offroad without issue.
 
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