2bbl to 4bbl

[JLAfarms]

Hi, I have a 1991 monterey 20.5 ft boat with a 305 mercruiser 2bbl carb and I am thinking of upgrading to a 4bbl carb and manifold. What will the performance difrence be? where would be a good place to shop for a combo deal if there are any.<br />Thanks,<br />Jerry

 

[Boomyal]

Re: 2bbl to 4bbl

Most common carburetor size would be a 600 cfm. A most common brand would be a 4160 Holley Marine. You can find them used on ebay. Other brands would be Barry Grant marine or Edelbrock marine. You'd be hard pressed to find them used.<br /><br />I don't know if they made oem 4 bbl mani's for the 305 but I'm sure that Edlebrock makes one. However, aftermarket aluminum mani's might not be the best for use in saltwater. I think some here do it and say they've had no probs. If you're going to buy new, I'd probably go for the Edelbrock pair.<br /><br />Now that I've said what is most common in the carb dept. I would be inclined to go with a 500 cfm carb. There are actually formulas available that identify the correct cfm for a given motor setup and I think you would find that 500 would be the ideal. The only mfg that make one is Holley and you'd have to buy new.<br /><br />A properly sized 4 bbl would be give you more poop and possibly better cruise economy. When you nail the throttle you get all four barrels. When you're cruising, you run on the primaries which are smaller than the two barrels on a 2bbl carb.<br /><br />Let us know what you choose and how it works out.

 

[Laddies]

Re: 2bbl to 4bbl

The 4 barrel 305 were rated 228/230 hp from merc. I think I would use a Edelbrock marine carb. I don't like Holleys on anything, but thats just a personal preferance---Bob

 

[bluewater19]

Re: 2bbl to 4bbl

Same manifold as a 5.7 350Ci. You can find used on ebay or new edelbrock performer anywhere that sells car parts. I Have an edelbrock 4bbl on one boat and a holley on the other. they both work well but the edelbrock was easier to tune.

 

[LubeDude]

Re: 2bbl to 4bbl

JLAfarms:<br /><br />Edit:<br /><br />Guess not!

 

[JasonB]

Re: 2bbl to 4bbl

Hey Boomyall, be careful on the statement about the primaries being smaller ona 4bbl than the 2bbl's. I thought the same, but I have a 600 Holley that Holley told me was pretty much 300cfm on the primaries. The 2bbl Rochester it's replacing is 300-325 and the stock holley 2bbl on most years of this engine were 300cfm, or my 4bbl without the secondaries. I have high expectations of my refurbed 4bbl....

 

[JLAfarms]

Re: 2bbl to 4bbl

I have orderd a edlbrock 600 marine carb and a performer intake now i just have to find the proper flame arrester any suggestions? I hope this upgrade will make a differance<br />Thanks,<br />Jerry

 

[Bondo]

Re: 2bbl to 4bbl

now i just have to find the proper flame arrester any suggestions? I hope this upgrade will make a differance

Search ebay...... 4bbl. Flame Arresters are Pretty Common........5 1/8th"s throat openning is what you need......It might take a couple searches,.. But They're on there......<br /><br />Ayuh,....... Once you get that Carb. Dialed In,... You'll Feel the Difference..........

 

[achris]

Re: 2bbl to 4bbl

Also be aware that 4bbl carb come in 2 flavours, spread-bore and square-bore. You need the right carb to match the manifold, or an adaptor.<br /><br />Square-bore has the primaries and secondaries about the same size. Spread-bore has very small primaries and ginormass secondaries.<br /><br />Rochies are spread-bore and Carter/Webers/Edlls are square-bore. Not sure about Holleys (shouldn't be put on a boat anyway!)<br /><br />Chris........

 

[Bondo]

Re: 2bbl to 4bbl

Chris,<br />The Eldebrocks are Another Carter AFB copy, Just like the Merc./Webers........<br />In the Smaller CFMs they are in fact a Spreadbore, in a Squarebore body.....<br />Bolts to a squarebore manifold,+ All..... No Adapters.......<br />The differences in the 625cfm carb,+ the 750cfm carb is the size of the Primaries.......<br /><br />Pretty Cool Carbs..... No casting joints or anything else below the fuel level.... Almost Can't Leak.......<br />And,.. With the Carter Strip Kit, Part # 10-201,.. It's Got to be the Easiest Carb in the World to Tune...................

 

[Boomyal]

Re: 2bbl to 4bbl

Originally posted by JasonB:<br /> Hey Boomyall, be careful on the statement about the primaries being smaller ona 4bbl than the 2bbl's.

So noted Jason. One of those ASSumption things.

 

[achris]

Re: 2bbl to 4bbl

Bondo,<br /><br />I (unfortunatley) have a Weber (which is a Carter AFB knock-off) on my 4.3LX. You're right about there being no gaskets below the fuel level. BUT, that doesn't mean they don't leak! That @#*&#$ carb is the reason why I'm here. <br /><br />Back in May last year I posted the problem I've had with it for the 10 years I've had the engine. When you shut the engine down, the carb continues to dribble fuel into the engine, by capillary action. All the experts I have talked to locally and a few I actually managed to get e-mail replies from, say that it can't happen. When I tell them I took the carb off and watched it do it, I never hear from then again!<br /><br />Yes, I've done all, and then some, of the checks suggested by all these experts and the guys here. This is the second Weber carb on this engine, the first was 9600 and the current one is a 9666S, both do the same thing. I have a couple of friends with the same engine/carb and they are constantly complaining of the same problem, and a few people on this forum have the same engine/carb and guess what? they have the same problem too. I even have a friend who runs an automotive repair shop here in Perth and he says the same thing is a known problem with Carter AFBs. Surprise, surprise! Mercruiser won't even acknowledge the problem and I can't get any answers from Weber USA.<br /><br />Things I've checked :<br />1. Fuel pump pressure, 5psi<br />2. float level. currently running at 2 mm BELOW spec.<br />3. I have put a heat insulating gasket under the carb.<br />4. idle speed is 650rpm in forward gear.<br />5. choke shutters are fully open at all times except dead cold.<br />6. even does it with the boat on the trailer (no rocking)<br />7. put spring loaded needle and seats in (only made the fuel consumption increase by about 20%! With the price of fuel the solid went back in!)<br />8. begged it to stop.<br />9. shouted at it to stop.<br />10. Went on iBoats for answers.<br /><br />If you have any suggests I'm all ears. In fact if you have, can we start a new thread....<br /><br />Chris........

 

[Bondo]

Re: 2bbl to 4bbl

Ayuh,......... You were editing Your post,.. While I was pecking mine out,... Cause, When I clicked Add,.. Yours was Different...... I Almost edited mine to say "But,.. You Already Knew That"..........<br /><br />Then I got to remembering that when I 1st noticed you, It was about the Weber Leak.......<br />It was after Your thread that got Me to Thinking about Mine.........<br /><br />Anyway,...... I'm at #11...... Live with It......<br /><br />The only time I notice it is on Saturday Mornings..... 1st time I light it, after sitting all week.....<br /><br />I'm Extremely Pleased with My Weber,.... I Think the next step Richer on the Springs is going to Finish the Tuning,(for a little while anyway)...... I've still got a slight stumbling at mid-range,..

 

[achris]

Re: 2bbl to 4bbl

Bondo,<br /><br />I'm pleased with the running performance of the Weber, it's just this starting thing that giving me the right royal sh...s. After I shut the engine down, it's a complete pain to restart. cranks for about 30 seconds before it catches, then a cloud of black smoke. Can't be doing the starter any good, and that's money in that smoke! I have put an outboard primer in the fuel line to prime it in the mornings, because if I don't I have the devil's own job of getting it to run. Couple of pumps on the bulb and she starts sweet as, when cold.<br /><br />Sorry, I don't accept #11.<br /><br />Chris.........

 

[Bondo]

Re: 2bbl to 4bbl

Ayuh,....... My boating Usually consists of launching at Daylight,+ Running out to the fishing grounds,+ Trolling til Dark............<br /><br />It was only after reading of Your issues that 1 day dragging the kids around on Toys, that I noticed the Rich restarts......<br /><br />I Also tried the outboard Primer Bulb trick,......It worked a few months,... Then 1 day, at the Most Inopportune Time,.. It Failed,...Sucked Inside Out...After Much Messing with, I plumbed it out of the line,+ All was Well..............<br />Since then,.. I Bypassed the Oil Pressure Switch.......Ayuh,..... I Know,.... Big Safety Issue,.... I'll take that chance.......<br /><br />Maybe Mine isn't leaking as Bad as Yours,... It Doesn't crank more than 15/20 seconds,+ ReStarts......<br />Cold Starts are Almost Instantaneous......

 

[achris]

Re: 2bbl to 4bbl

Bondo,<br /><br />Don't tell anybody else, but I've bypassed the pressure switch too. Things a bloody nuisance!<br /><br />Chris..............

 

[Stan's Customs]

Re: 2bbl to 4bbl

Greetings Gentlemen...<br /><br />Just noticing the carb post, thought I'd add my 2cents. <br /><br />I see many post acclaiming the Edlebrock type (AFB) aftermarket carbs....Totally amazing to me that other users have a single good thing to say about them. I've had two...thought the first one was just a lemon....bought another a couple of years later for another application...same thing.... junk in my opinion. I gave the first one away to a teenage neighbor boy when it had 2 hours on it. The second one ticked me off so bad I dismanteled it with a 2 lb shop hammer.<br /><br />I've since kept to Quadrajets....everyone of which has provided the proper starts, great idling and super performance that I expect in a quality fuel delivery system. These carbs are referred to by some as Quadrajunks....however you will never hear that from a competent carb rebuilder ...they all regard them highly.<br /><br /> The idle circuit and small front venturi's yield fuel efficency that is second to no other 4 bbl carb....and when power is needed few other carbs will give the punch a quadrajet does when nailed to full throttle. Lastly they will hold their tune...unlike Holleys and others ...Of course if they are easy to tune that is helpful, I guess. I personally think they are all easy to tune....I just hate to have to do it more often than I do a tuneup.<br /><br />Anyway...my 2cents...Best Regards

 

[LubeDude]

Re: 2bbl to 4bbl

Stan:<br /><br />Instead of just saying you had problems, how about letting us in on what kind of problems you had. I feel it was simply a tuning issue.

 

[joshljoshl]

Re: 2bbl to 4bbl

I have a '98 Regal 242 with a Volvo SX 220HP. It's a Chevy 305 with a 2bbl carb and I'm very interested in increasing the cruising MPG, as well as improving my holeshot getting on plane. It seems going to a 4bbl carb would help in both cases. I have never been inside of an automotive carb, but I have tuned many motorcycle, atv, and other small engine carbs. Is it just a matter of replacing the intake manifold and carb? How do you determine the proper jetting? What sort of special tools would I need for tuning things? <br /><br />Also, does anyone know how to subscribe to a thread for email notifcation without having to first reply/post to it?

 

[Stan's Customs]

Re: 2bbl to 4bbl

Sorry LD...<br /><br />Primarily, as per above.... hard restarts when hot as when water skiing....and in my humble opinion poor performance compared to a Quadrajet. The carburetor in general performed mediocre....some might have tolerated its performance...the engines that I had them on were fresh rebuilds and mediocre was not acceptable. <br /><br />I don't believe the problems were tuning issues either, just the nature of the beast. Once again some might not have considered the problems I had worrysome....some would though.....I just happen to be one of those and am surprised that more haven't vented their lack of satisfaction with them based solely on my personal experience. Also once a good rebuilt Quadrajet was installed, both engeines performed as they were expected to.<br /><br />Not to start some squabble...just my humble opinion, but nothing I own will ever see one of these carbs again. <br /><br />...once or twice but never thrice, my ole' Daddy used to say.<br /><br />Much respect to those who have other opinions too......I hope every one who has an Edelbrock carb is tickeled pink with it and wouldn't even consider something else. Nothing like spending money and regretting the expenditure.