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Wrong Carb for Marine Use?

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Mark Christensen
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Wrong Carb for Marine Use?

Post by Mark Christensen » Wed Jul 17, 2013 12:27 pm

Right now I have an Indmar 454 on my 24' Sportsman. The carb on it is a holley 12r 554B. The problems I've been having lately is that it will start fine, and once I run it at about 2500 RPM's for 10 minutes or so I get power loss, then the engine pops and picks up speed again. Some days I can go for 2 hours with nothing, then it really starts acting up doing what I describe. Then the idle also gets really finnicky. I've replaced the pumper valves? I think that's what they are called, and had a good mechanic tune the mixture screws for me. The engine only has 18 hours on it by this time, so maybe it's just breaking in, but it's starting to get a little irritating. I read somewhere that that 554B is an automotive carb, not a marine carb which makes a difference? Anybody? Thanks!
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drrot
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Re: Wrong Carb for Marine Use?

Post by drrot » Wed Jul 17, 2013 2:36 pm

No photos??
Jim Staib
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Mark Christensen
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Re: Wrong Carb for Marine Use?

Post by Mark Christensen » Wed Jul 17, 2013 2:40 pm

Good point Jim. I'll post photos this weekend when I'm at the boat.

Mark
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Re: Wrong Carb for Marine Use?

Post by jim g » Wed Jul 17, 2013 7:20 pm

Take a picture with the flame arrester off.

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Re: Wrong Carb for Marine Use?

Post by Peter M Jardine » Wed Jul 17, 2013 8:16 pm

The actual holley number for that carb is R50483.... which should precede your 12R number. The Holley model number is #4010. It is a marine 600 CFM carburetor. 600 cfm is a tad light IMO but your likely issue is either the carb is sucking air somewhere, or dirt. I always go for the dirt diagnosis first. Marine carbs sit around for a lot of the time and stuff that would keep mobile has a chance to settle and stick inside.

The easiest way to tell a marine carb is to look at the vent tube..... an automotive carb vents straight up, and a marine one vents back into the bowl.

Here is a 4010 pic and you can see the vent tube orientation

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Re: Wrong Carb for Marine Use?

Post by Peter M Jardine » Wed Jul 17, 2013 9:46 pm

Yeah, it's not a fan favourite, and there are a lot of other carbs to choose from that are far less hassle. Edelbrock knockoffs of the carter are a very good carb, but so is the Holley M series... though a tad pricey. I would rather see a little larger carburetor on that engine...650 cfm. That new M series Holley has had good reports.

Apparently that 4010 is know for vapor lock as well, which could account for why it takes a little while to make it sputtery..maybe a insulating spacer would be helpful, (and cheap), but overall there are better carburetors.

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Mark Christensen
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Re: Wrong Carb for Marine Use?

Post by Mark Christensen » Thu Jul 18, 2013 6:42 am

how do I know which one will fit my engine? I'm mechanical, but carbs are the bane of my existence... I really appreciate the help guys.
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Re: Wrong Carb for Marine Use?

Post by Greg Wallace » Thu Jul 18, 2013 7:31 am

Check to see if you have a bronze inlet filter at the float bowl fuel line connection. Assuming you have a filter ahead of the carb I wouold discard the bronze inlet filter if it is there.
Greg Wallace 23 Custom 22166 former Chris-Craft dealer Russells Point, Oh.

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Re: Wrong Carb for Marine Use?

Post by mattbyrne » Thu Jul 18, 2013 8:47 am

Mark,

Check out this site
http://www.skidim.com/products.asp?dept=1115

They a very knowledgeable on Indmar. I got stuff form them for our Supra Inboard.

Matt

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Re: Wrong Carb for Marine Use?

Post by Peter M Jardine » Fri Jul 19, 2013 9:43 pm

Mark Christensen wrote:how do I know which one will fit my engine? I'm mechanical, but carbs are the bane of my existence... I really appreciate the help guys.
Without me yapping off and missing something, here is a good primer on your carburetor brand

From Holley Marine Performance Products
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 carburetor/flame arrestor combination
to contain the backfire. For this reason a gasket is not used between the carburetor airhorn 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.

Carburetor Descriptions Performance Show Carburetors
Holley Performance Show marine carburetors are available as four barrels in either square (Model 4010) or spread bore (Model 4011) flanges and also as a two barrel (Model 2010) with the 2300 flange. These are universal marine carburetors that can replace existing Rochester Quadra-Jet, Rochester 2GC, Carter AFB/AVS and Holley two and four barrel carburetors that were original equipment on various marine engines. These carburetors come equipped with an electric choke and the four barrel models have dual feed fuel bowls. The 5" airhorn of these carburetors will allow you to use the existing flame arrestor of the old carburetor. Some minor fuel line routing will be required to accommodate the dual feed fuel line.

The Holley model 2010, 4010 and 4011 marine carburetors all utilize annular boosters. This unique design provides for a relatively stronger vacuum signal and provides a very smooth and linear transition to the main circuit with superior fuel atomization. Throttle response is "Right Now" (great for pulling skiers up) and, once on plane, fuel economy is enhanced. An added benefit of these carburetors' design is the ability to easily "best Jet" them without removing the carburetor from the manifold. Simply remove the top airhorn cover casting. The fuel level is below the casting line so there is no danger of fuel spillage. The carburetor main jets can be accessed on the floor of the respective fuel bowls.

Standard Holley parts are used in these carburetors so jets, power valves, vacuum secondary diaphragms and springs, etc. are no problem. Special marine carburetor rebuild kits are available for these, and all Holley marine carburetors. This catalog has the complete listing of carburetors and kits. Also, special Holley chrome dual feed marine fuel lines are required for the Models 4010 and 4011 carburetors. These are listed with the respective carburetors in this marine section.

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Mark Christensen
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Re: Wrong Carb for Marine Use?

Post by Mark Christensen » Mon Jul 22, 2013 12:21 pm

well it sounds like my carb isn't so hot. I found what I think to be a decent replacement:

http://www.ebay.com/itm/HOLLEY-4160-600 ... e7&vxp=mtr

Anybody have any thoughts on this?

Mark
1961 24' Chris Craft Sportsman - CUA-24-0007C
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Re: Wrong Carb for Marine Use?

Post by quitchabitchin » Mon Jul 22, 2013 6:51 pm

That is probably a suitable replacement, but I am partial to Carter or Edelbrock. I prefer the ease of tuning via metering rods and jets. Once you get the right jet, you can really fine tune them without taking the whole carb apart and just swapping the metering Ross to a smaller/larger rod. You can also change the spring rates on the metering rods to adjust according to the vacuum on each engine.

Carbs are like anything else, you will find Edelbrock or Holley people just like you will find Ford or Chevy folks. They are both quality products, it's just a matter of which camp you're in.
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Peter M Jardine
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Re: Wrong Carb for Marine Use?

Post by Peter M Jardine » Mon Jul 22, 2013 9:10 pm

I agree, I like the carters.... nice and simple, and although I have a boat with each brand on it. The edelbrocks are really a good carburetor.

While I appreciate the value of a used carburetor, what you really need is a good carb guy to go over the used one when you get it, or you may be right back where you started. The 4160 would be a better carb for your application than the one you have by quite a bit.

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Re: Wrong Carb for Marine Use?

Post by mfine » Tue Jul 23, 2013 7:03 am

Eddlebrock 1410 gets my vote.

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Paul P
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Re: Wrong Carb for Marine Use?

Post by Paul P » Fri Jul 26, 2013 3:57 pm

Even running a 454 at 5000 rpm, the 600-cfm #1409 Edelbrock is "the" preferred carb, and I say this after doing extensive research for a hotted up 427 and having purchased a 750, only to sell it at a slight loss and purchase the smaller 600 carb. Going to the 750 is not advised. The signal you get from the smaller carb wil be superior and you'll get great lower speed running. The notion of a 750 just does not apply here, IMHO, because 5000 rpm won't require any more than 545 cfm with a volumetric efficiency of .83 even when pumping air at 5000 rpm (and how offen are you planning on doing that?).

With pulsation like you mentioned there can be numerous things affecting it, maybe more than one simultaneously including: clogged pick-up tube, clogged filter, clogged anti-siphon valve, failing fuel pump, carb floats improperly set, dirty carb, and a distributor that won't properly advance.

Good luck hunting it down. It has to be one or more of these issues.

best,

Paul
1956 17' CC Sportsman, 300-hp
1957 17' CC Sportsman, 95-hp
1966 20' CC fiberglass Sea Skiff, 210-hp+
1973 23' CC Lancer inboard project, 427/375-hp.
1966 38' CC Commander Express, 427/300-hp(2)

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