Unlimited jd

iTrader: (5)

I worked on a boat recently that had automotive carbs on it that were installed by a well known respected cig dealer. How many guys are running automotive fuel pumps?

gmhdfan

I still use a marine starter. an old school one, cast iron nose, bigger fields, welded armature, and works fine. But from what I remember the only thing different is the rubber flap. But I see a lot of people using automotive mini gear reduction starters.

87MagnumII

When I was building my engine I made sure that I ordered a marine carb and fuel pump. Starter is also marine. To hell with all the legal issues, I would feel terrible if I hurt my kids by being a cheap ass. I don't know the differences in the street and marine stuff and really don't care, there is a difference for a reason and I want to make sure everybody is as safe as possible

ezstriper

I have had marine carbs apart, saw no difference in throttle shafts, no seals, etc...only the finish(painted) pcv plugged and J tubes on the holleys, not used on Q-jets or the webers aka edelbrocks....calibrations are the only real difference

keith2500hd

the trottle shafts are teflon coated(green coating on Q-Jets) orings or teflon sleeve/sprial rings, this is to prevent backfire from going out throttle shafts. the marine components used to have rigerous testing in lower to upper explosive limits in test cell. what may look simple has been tested to minimize flame front travel. most racing carb shops seem to use the same throttle shaft setups as marine carbs, helps control a/f metering flow. metering blocks will have larger fuel passages, thats why modified racers are after rochester 2gc's all the time.

BBCLiberator

iTrader: (2)

This post is the winner for me. I mean, just for the peace of mind alone I'd do it. Any other advice is bad advice, can you do it? Sure. Does it make it a good idea? No. Lots of people use incorrect parts and I'm certainly not here to lecture, but the fact that you are asking already means you know it's not the best idea. I haul my family around on this thing and spend more on gas in a good week than the difference in part cost. Maybe I'm completely wasting my money and I don't care, that coast guard stamp of approval (even though it may mean nothing to me) means something so somebody. If something were to ever happen I want a clear conscience.

Do you want to worry about it, or not? That's really up to you.

DYVMASTER

besides the J tubes if it is truely a marine carb they have some air bleed holes inside slightly enlarged. Also the throttle shafts have a channel cut in them before they come out through the body of the carb so fuel can't run out between the body and shaft.

ThisIsLivin

Where does one find a 950CFM or larger marine carb? I've been told by several high performance engine builders to stay away from J-tubes as the air velocity going past can change the fuel height. I have a Pro-Systems 950 that has a piece of Tygon tubing connecting the 2 vent tubes that extends up away from the carb with holes in it. Pro-Systems builds carbs for blow through applications so they know how to build a sealed carb.

CigDaze

To address the differences between automotive carbs and marine carbs, I submit the following:
http://www.uscgboating.org/regulatio...rds_partf.aspx

These are the USCG regulations which govern marine carbs and their associated tests to make them marine-worthy. You can perform the modifications yourself, and be in "compliance" for your own peace of mind, but it will never actually replace the certification itself - which is what you'll need in case something ever goes wrong and the blame is placed on non-approved, non-marine-grade equipment.

rmbuilder

I would caution against the use of J-tubes/ inverted orifice vents in any carbureted application. With the J-tube extending into the airstream, as air speed increases into the body, pressure at the inverted opening decreases. The pressure drop is transferred to the surface of the working fluid in the bowl. Proper fuel metering is dependent upon the correct differential at the bowl vs. the opening at the jet. The imbalance can result in incorrect mixture distribution. Ideally you would have the pressure at the working fluid (vent tube) stable relative to atmospheric allowing the jet orifice size to properly meter the fuel dependent upon the pressure drop in the venturi. The use of the J-tube can potentially result in a top end lean condition.
If you have concerns regarding issues with the CG or insurance carrier the balance tube pictured below may be a preferred option.

Bob