J tubes are not a Coast Guard requirement, neither are sealed throttle shafts. This was previously covered in another thread. You can look up the tests needed to pass the CG requirement, it's no big deal for a modern carb. If you've got a policy that wouldn't pay out if your boat sank and had an automotive carb on it, you need different insurance.. They'd have an awfully hard time proving the carburetor caused you to sink..

+1

Touching on the alt differences. The marine alts have the screens in the rear vent cover to stop all of those sparks that are always flying out of the back of our alts and igniting the gas fumes spilled out by those auto carbs being used. They had to make some sort of modification to the parts to label it "Marine Use" and double the price, seriously?

with a holley, J tubes, jetting are only real differences..there are no seals on the throttle shafts on the marine ones I've pulled apart, they sometimes add a elec choke..but thats about it...

I had a custom carb built for my boat from a very reputable carb builder. It was a standard Holley HP 4150. When I got carb to my car I noticed there were no J-Tubes installed. I turned around with the carb and went back in to the shop. I said this was suppose to be a Marine carb! They're response was, it will run better WITHOUT the J tubes! They gave me a set of J tubes and said they would install them if I wanted but they assured me the carb was 100% safe to run in a boat. Like Haxby stated this has been covered many times in more detail. I just wanted to share my experiences on this.

my "marine" holley has no uscg stamping on it to identify it as a "marine" specific carb. it has regular holley catalog numbers on it. i bought it new.

it's not so much a "seal" but a groove machined into the shaft to keep fuel from spilling onto the intake in case of flooding.

there IS a difference!

this said, any holley can be converted for marine use. you need to contact a real holley carb tuner shop to have this properly done.

in ohio we have a shop called "cfm" the guy's name is dale and he's in litchfield ohio. here's the website......

http://www.google.com/url?sa=t&rct=j...9rkdA69EayK39w

once you use cfm you will not go anywhere else!

Had a buddy who's Q-Jet was acting up this summer. Dang thing would spew fuel all out the top around the Acc pump rod, and past the throttle plate shafts onto the intake. Original Merc equipped carb.

How many guys that keep on saying Ins will be denied if they see a non 'marine' carb , or even an overloaded tow vehicle, have actually had their ins denied because of such when involved in a claim? No assumptions.
I've yet to read of any actual denials. Getting to the point one can almost guarantee the next reply after someone ask about over the limit or non marine stuff.

+1 When was the last time you got pulled over and water patrol or coast guard asked to see your carb.

We tried a couple of their carbs; in my opinion ProSystems builds a better piece in terms of being really well tuned right out of the box and smoother transitions through the circuits.

i've heard great things about prosystems as well.

the point really is.....develop a relationship with a carb tuner and go from there.