The reason it quit on you and the fact that the carb is too small are two different issues.   Too small of a carb will not starve the engine of fuel.  And yes, you need more carb.  I'd run a dominator on
A 540

X3 on the bigger carb, I would doubt it seriously if you ran it out of fuel running balls out, something else is amiss....

The 750 will use less fuel than the 850, so it would stand to reason that there is either something wrong with the 750 mechanically, or another system has a poltergeist.

GT

1050 or 1150 Dominator is what I'd run. Sounds like a pretty badass motor. Problem is, you should change the intake to a dommy flange as well, or you'll need adaptors which might affect the impact of the dominator. Might want to consider a 950 4150 base carb.     I also think the 3/8 fuel hose is just fine. Personally, and I like mechanicals over electric on these things, I only run Clay Smith mechanical pumps. I really view the Summit brand as just cheap Chinese copies of a Holley (The Mr Gasket you tossed is the same thing as the Holley). Be careful dealing with them over the phone as they are interested in their Gross Margin as much as anyone. It's important to remember we operate these boats in the 3000-6000 rpm range ALL THE TIME, not the same as a street engine. 

I had the same dying out at WFO part "like it was running out of gas" with Pickle at the end of last year and part of this year. Turns out it was a combination of an internal vaccum leak on the 750 (Warped metering block), a PCV valve and a serious vacuum leak at the carb base (also warped). That carb has been retired to "parts carb" status,  . It now runs an 850 Vac Sec'y just fine, and might be just a coincidence, but the Vac advance HEI was replaced with a Mechanical Mallory Unilite, 6AL box and Procoil as well. This is on a pretty mild 454 Chebbie though, but holds 5200 RPM all day long if you want it to. 

Ray

I thought the Summet racing fuel pump was a pretty good pump? Some friends I got it from seemed to think so. Are they really just Chinese crap?

That's just my opinion. I don't know where they source their house brands from really. When I bought Moo, it had a fresh 460 with a thrown #1 rod. The engine had a Summit pan, roller rockers and fuel pump on in. The pan seemed pretty thin and cheesy to me, so it's just a parts bin now, and the kids made christmas tree decorations out of the roller rockers..........

The fuel pump is still laying around here somewhere, never used it. I put a Clay Smith on the boat when I built it. With twin 750's, would hold 7 PSI forever on 3/8" hoses and a pretty restrictive electric tank selector valve. 

On a Mini Day though, enclosed engine compartment, motor sounds much milder than it's 540 CI would indicate, you're still going to have to have to go with a Dominator to get above the 850 CFM for a marine rated carb. I'd be doing it! All stock marine 460's came with 750's, and from what I've seen and experienced, an 850 wakes them up a LOT. You've got a helluva lot more cubes (around +20% ) even if the cam is about stock.

If you do this, or, if it were "ME", I'd be looking at the Stealth intake as well, or a Victor with a dommy flange and the 1050 Marine Dominator. They do not make a 950 CFM 4150 in a marine version. There's more to these marine carbs than just the "J" vent tubes!  And since I seem to have, and be gaining more, experience with burning boats, I will not run a street/strip carb on any boat, enclosed engine or not.    I'd also be looking at Lightning water jacketed headers............

Ray

thread jack

Hey 78 Crusader, in SoCal right now, but boat is in Texas. Home lake is Ray Hubbard. Thinking carb too. My 460 BBF has a 650 and needs more. Seems like your motor could use a larger carb. Your starvation problem sounds familiar. My boat will run great for an hour of ragging, and then die. Still trying to sort out the gremins.

The differene of a marine carb is the vent tubes, if the carb over vents the fuel goes directly back into the carb rather than the boat. You can buy them ( J tubes) from holley or make them.

guys, i think we are looking at his cid 540 and saying that thing needs a BIG carb. now we know it wants more due to him changing to an 850 and picking up rpm and mph.

now that being said, what heads and cam do you have? you are running logs and the dominator may be too much depending on the heads and cam.

pump gas? solid cam or hyd

The differene of a marine carb is the vent tubes, if the carb over vents the fuel goes directly back into the carb rather than the boat. You can buy them ( J tubes) from holley or make them.

This from CP Performance. There's more to it than the vent tubes. Special throttle shafts, seals...........and more.  

READ BEFORE YOU BUY!
If it looks like a duck and quacks like a duck, it must be a duck. Right? Well, maybe. Carburetors are carburetors, but only marine carburetors should be used on boats. It's true that marine carburetors started life as regular automotive carburetors but then each took divergent paths.

Marine carburetors have certain modifications that make them uniquely adaptable and legal for marine usage. "Legal" meaning that it has the ability to pass the U.S. Coast Guard test for marine carburetors. Folks, I'm not talking about Paris Island here, either. The main qualification that a marine carburetor must meet (as set down by the U.S. Coast Guard) is that if the carburetor should "flood" only .5cc of fuel is allowed to escape in a period of 30 seconds. There's also a "backfire" test which confirms the ability of carburetors/flame arrestor combination to contain the backfire. For this reason a gasket is not used between the carburetor air horn flange and the flame arrestor. It's possible that this gasket could become saturated with fuel (if the carburetor should flood) and become a potential fire source as a result.

The primary areas of a carburetor that require some sort of modification to meet these requirements include the fuel bowl vent tubes and throttle shafts. The vent tubes of a marine carburetor are bent inwards so that the tube looks like an inverted "J". These tubes oftentimes are referred to as "J" tubes, as a result. The reason for bending the tubes inward is that if flooding should occur, the fuel that would normally come out of the fuel bowl vent tube is rerouted back into the carburetor.

Throttle shafts also get special machining attention. Shafts are "grooved" and "slabbed" to prevent fuel from exiting out the throttle shaft if flooding should occur. When a carburetor floods fuel will end up "puddling" on the throttle plates. A non-marine carburetor will allow this fuel to seep out of the throttle shaft ends and onto the manifold. This is not allowed on a marine carburetor because normally the engine is situated in an enclosed bilge where potentially deadly gasoline fuel fumes can accumulate. Throttle shafts that are "grooved" and "slabbed" channel the flooded fuel safely down into the intake manifold. With no raw fuel allowed to puddle on the manifold outside the carburetor, there is no chance of deadly fuel fumes to accumulate in the bilge and no chance of explosion or fire.

For these reasons an automotive carburetor should NEVER be used in a marine application

Ray

This from CP Performance. There's more to it than the vent tubes. Special throttle shafts, seals...........and more.  

X2   

How many folks on here are running "marine" carbs?

Out of our five boats (no, not just me...) three have marine spec carbs, the two open engine jets have automotive/high performance carbs...

Realistically, it has to have an SAE designation for a Coast Guard rating to even apply, not just have the right "pieces"...They are looking for the sticker/tag on them, much like CARB exempt numbers for SMOG...

GT

How many folks on here are running "marine" carbs?

Every boat I have, had (Save for the one that caused this thinking), or will have.

My only exception is a current project motor, but I'm quite sure even the Coast Guard is gonna have trouble figuring out if a Crower MFI unit meets standards or not. It will have a rather large flame arrestor though! 

Saving a couple hundo on a carb isn't worth losing a $5k boat that most of us have over $10K in. Let alone a life, IMHO.

I will give you that most of us are running street carbs, but for whatever reason, probably the U-Tube video, I get pics and video sent to me from everywhere of burned up jet/V-Drive boats. Latest was a Scorpion in Missouri I think.    It happens much more often than you think!

Ray