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TOPIC: Upgrading from 2 barrel to 4 barrel carburetor

Upgrading from 2 barrel to 4 barrel carburetor 04 May 2016 15:12 #1

  • TheBaalmans
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I have 5.7 Mercruiser mated to Bravo III in my 2459 Rendezvous. I assume that replacing it with a 4 barrel would be feasible. I have replaced my stock 3x3 24" props with XR 4x3 23" stainless props and added trim tabs. Looking for a bit more power without having to make really major modifications. According to inspection the engine had less than 300 hours on it, but unverifiable since the hour meter was non functional when I purchased it. Since then I've put 76 hours on it. I'm aware fuel consumption will rise and I might have to swap intakes. Haven't put boat in water yet this year to try out trim tabs as trailer modifications and repainting are taking a bit longer than planned

Anyone done it? Is it worthwhile? I've done it before with vehicles I've owned prior so engine work isn't new to me. This is still my first boat so I thought I'd ask people with more knowledge about it before I really start getting serious about it.

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1999 Bayliner Rendezvous 2459
5.7L Bravo III
"I'm Fine"
Lost Wages, NV

Upgrading from 2 barrel to 4 barrel carburetor 04 May 2016 15:55 #2

  • Ruffryder
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Well worth it! 2 barrel Mercarb/tiny intake Genuine POS IMO.
Edelbrock 1409/intake would be nice.

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Joon, Kathy, Jaden & Tristan
93 3058
92 2855
91 Fourwinns 205
Longbranch WA
Life is Good

Upgrading from 2 barrel to 4 barrel carburetor 04 May 2016 16:10 #3

  • SprinterX
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Pretty sure your 1999 5.7 is a Vortec engine. This topic has been discussed several times so a quick search should keep you reading for a little while.

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Sea Venture
2000 3055, 5.7/B2, 18x23" props
Cruising the PNW and beyond.
DIYC, Riverhouse Marina
MMSI 316029971

Kirk :)
Drinks well with others. ;)

Upgrading from 2 barrel to 4 barrel carburetor 04 May 2016 19:15 #4

  • kkeever
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I upgraded a friend boat from 2 to 4 barrel a while back, his wife was against it due to fuel use concerns. Turned out that not only did the boat perform better it got better fuel economy as well. It also got on plane better/faster, it cruised at a better rpm too. He still has the boat and tells me he should have made the change sooner.

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Kelly Keever
Lavon, Texas
1998 Bayliner 2855 Ciera
7.4L MPI
Bravo 3

Upgrading from 2 barrel to 4 barrel carburetor 09 May 2016 19:04 #5

  • TheBaalmans
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Thanks all! I can take it from here. Will get Edelbrock carb/intake and swap out either this season or over the winter.

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1999 Bayliner Rendezvous 2459
5.7L Bravo III
"I'm Fine"
Lost Wages, NV

Upgrading from 2 barrel to 4 barrel carburetor 09 May 2016 20:41 #6

  • Alaskanmutt
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You also need a different throttle linkage mount

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Boatless at this time

A veteran is someone who, at one point in their life, wrote a blank check made payable to "The United States of America," for an amount of "up to and including their life."

Upgrading from 2 barrel to 4 barrel carburetor 09 May 2016 22:07 #7

  • TheBaalmans
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Alaskanmutt wrote: You also need a different throttle linkage mount


Been checking on michiganmotorz.com and noticed that, thanks!

If the boat will never see salt water, will it still need the lined intakes?

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1999 Bayliner Rendezvous 2459
5.7L Bravo III
"I'm Fine"
Lost Wages, NV

Upgrading from 2 barrel to 4 barrel carburetor 11 May 2016 19:07 #8

  • fishaman
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I have replaced mine about 5 years ago. I have a full fresh water cooling system, so I do not care about inlays. The list of parts I used included:
- Edelbrock 1409 carb,
- Edelbrock aluminum intake manifold (Performer, dual plane)
- new throttle bracket (bought on ebay, originally from 1992 5.7 Magnum with Wever 4 barrel carb)
- new bracket to hold Mercathode, main breaker, and slave solenoid (easy to manufacture from a piece of 1/4" aluminum, attached to rear carb studs, works great with original engine harness)
- new fuel line from pump to carb (can use a 3/8 CG approved A1-15 hose)

Works great, smooth, lots of power, and no problems so far.

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Alex
1997 2859, 7.4 MPI, Bravo II
1993 2452, 5.7 Bravo II - SOLD

Upgrading from 2 barrel to 4 barrel carburetor 13 May 2016 10:47 #9

  • 88fourwinns
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For the use a boat gets (high rpm, constant load) the 4bbl makes sense. When you run on the primaries it will probably get somewhat better fuel economy, and when you need wide open throttle, its nice to have that exta push in the back from the secondaries. My 4.3 came with the 4 bbl Quadrajet and I'm glad it did. They are a complex carb but when set up well they work very well.

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88 Four Winns 200 Horizon 4.3 OMC
98 Jeep Grand Cherokee 4.0/Selectrac
07 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Long Island Sound Region

Upgrading from 2 barrel to 4 barrel carburetor 21 Jul 2016 20:44 #10

  • TheBaalmans
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I'm moving forward with the project. I've picked up a Holley 1475 marine carb with fuel line (650cfm vacuum secondaries from an OMC 5.7L off craigslist for $100), an Edelbrock Performer 2116 aluminum intake manifold (Ebay - $69), throttle linkage adapter, throttle bracket, gaskets, sealant, studs, manifold bolts, and rebuild kit for the carb. Also snagged some new plugs NGK BPR6EFS. I replaced the distributor and wires when I purchased it in 2012.

The only things I still need to possibly get/manufacture is a spark arrestor and bracket for Mercathode/breaker/slave solenoid. Will look at them later to see if they will work or not. I'm aware the intake manifold isn't marine with lined passages, but since the boat will never see salt water didn't see a problem.

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1999 Bayliner Rendezvous 2459
5.7L Bravo III
"I'm Fine"
Lost Wages, NV
Last Edit: by TheBaalmans.

Upgrading from 2 barrel to 4 barrel carburetor 21 Jul 2016 21:16 #11

  • Castaway
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I have a 4 barrel Weber and seem to spend all my effort trying to keep the secondaries closed. ;) $$$

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Bryan
1997 2858 7.4 B2
1992 Hewescraft
Puyallup, WA

Upgrading from 2 barrel to 4 barrel carburetor 21 Jul 2016 21:49 #12

  • TheBaalmans
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I'd be buying a new spark arrestor. My fabricating skills are no where near that good! That's only if my current Mercruiser one doesn't fit.

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1999 Bayliner Rendezvous 2459
5.7L Bravo III
"I'm Fine"
Lost Wages, NV
Last Edit: by TheBaalmans.

Upgrading from 2 barrel to 4 barrel carburetor 22 Jul 2016 01:33 #13

  • desuch
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yep Edelbrock 1409 used the manifold that was on the engine just needed to purchase a adapter plate $20 ,had to get a differet spark arrester and do some modification

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1988 flybridge trophy bayliner 2556 ,mercury 5.7 lit. OMC cobra out drive 76 hrs. on new package,
located in ketchikan ak,name DOMINION
Last Edit: by desuch.

Upgrading from 2 barrel to 4 barrel carburetor 22 Jul 2016 01:41 #14

  • Amadaies
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desuch wrote: yep Edelbrock 1409 used the manifold that was on the engine just needed to purchase a adapter plate $20 ,had to get a differet spark arrester and do some modification

You are not getting the full benefit of the 1409 at all. You are still restricting your airflow through the 2bl manifold.

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Pat. Sandpoint Ida
1984 Bayliner Ciera 24.5 Volvo Penta 5.7/290DP

Upgrading from 2 barrel to 4 barrel carburetor 23 Jul 2016 01:13 #15

  • Dadrock33
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Can this be done on a 2003 5.0 L? It almost sounds too easy but I realize it isn't . . .

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1998 Avanti 3685 - "Dad's Dream" w 454 Mercs - just a rockin' an'a rollin'
Former - "Home Aweigh" 2003 - 2452 Bayliner Cierra Classic Hardtop Cruiser
WQQM835 MMSI: 338147209
James H. Stradling

Upgrading from 2 barrel to 4 barrel carburetor 23 Jul 2016 01:17 #16

  • Ruffryder
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Yes it can be

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Joon, Kathy, Jaden & Tristan
93 3058
92 2855
91 Fourwinns 205
Longbranch WA
Life is Good

Upgrading from 2 barrel to 4 barrel carburetor 23 Jul 2016 02:35 #17

  • desuch
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good point about airflow, might change latter but for now happy with performance

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1988 flybridge trophy bayliner 2556 ,mercury 5.7 lit. OMC cobra out drive 76 hrs. on new package,
located in ketchikan ak,name DOMINION
Last Edit: by desuch.

Upgrading from 2 barrel to 4 barrel carburetor 01 Aug 2016 15:09 #18

  • TheBaalmans
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Did the swap this Saturday, changed plugs, reset the timing, and put in the intake and carb. Had my brother tune the carb. Took the boat out on Sunday for a run down the river. Holy crap! What a difference it made! The throttle response is ridiculously quick and responsive. When I put the trim tabs on at the beginning of the season I though I was getting on plane quick. Now, I throttle up and and I can't get the trim tabs lifted fast enough because it's on plane NOW. Very happy with the upgrade, woke that engine right up. That poor engine has been starving for air/fuel for way too long. I knew it was running lean as the engine had dieseled (continuing to run after being shut off) a couple of times this season and the plugs showed it when I pulled them.

The downside is I am probably going to have to re-prop the boat. I'm running a set of Mercruiser XR 23 pitch 4x3 stainless props and my WOT RPM was around 4500. Now, it's between 4800 and 5000. The sticker on the flame arrestor cover states WOT RPM should be between 4400 and 4600.

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1999 Bayliner Rendezvous 2459
5.7L Bravo III
"I'm Fine"
Lost Wages, NV

Upgrading from 2 barrel to 4 barrel carburetor 01 Aug 2016 15:58 #19

  • Ruffryder
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Yup yup night & day

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Joon, Kathy, Jaden & Tristan
93 3058
92 2855
91 Fourwinns 205
Longbranch WA
Life is Good

Upgrading from 2 barrel to 4 barrel carburetor 01 Aug 2016 16:25 #20

  • bhawes
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I'd considered doing this to my 4.3 a few years ago, but read that the 4.3 that came with 4bbl also had an upgraded cam. The package added about 30 hp. The cam upgrade erased my desire to upgrade to the 4bbl. My boating use has changes somewhat and I know longer have any need for the extra hole shot that the 4 bbl would give.

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Bob Hawes.
Kelowna, B.C.
1998 Trophy 2052 WA
4.3 Vortec, A1 G2

Upgrading from 2 barrel to 4 barrel carburetor 01 Aug 2016 16:47 #21

  • 88fourwinns
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The 4bbl is a nice upgrade on the little 4.3. Mine has the original Q-Jet and properly set up it performs very well. The secondaries give a nice push in the back and muscle car sound at the top end. Only down side is a Q-Jet is much more complex to rebuild than a simpler 2bbl.

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88 Four Winns 200 Horizon 4.3 OMC
98 Jeep Grand Cherokee 4.0/Selectrac
07 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Long Island Sound Region

Upgrading from 2 barrel to 4 barrel carburetor 01 Aug 2016 16:55 #22

  • Ruffryder
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Will make the biggest difference on a Mercruiser Vortec 250HP 2 barrel carb/ Intake engine...

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Joon, Kathy, Jaden & Tristan
93 3058
92 2855
91 Fourwinns 205
Longbranch WA
Life is Good
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