Approval on performance upgrade for 4.3 mercruiser

[Heybuddy]

Hey fellas I was browsing some old post and saw some talk about upgrading a 4.3L Mercruiser from 2 bbl carb and intake to 4 bbl .. I found these parts hoping there just bolt on and minor air/fuel ratio adjustments? Any advice would be great?? I have engine number B403048

 

[aimlow]

Even tho it's just a Chevy, intake manifold bolt pattern must be matched to the heads on your engine. The height of the flame arrestor must fit in your engine box. If your exhaust goes thru the outdrive, expect back pressure to affect high end performance.

 

[Heybuddy]

Even tho it's just a Chevy, intake manifold bolt pattern must be matched to the heads on your engine. The height of the flame arrestor must fit in your engine box. If your exhaust goes thru the outdrive, expect back pressure to affect high end performance.

Is the back pressure going to be an issue? Can I tune around it? Can I replace exhaust manifolds then also?

 

[Scott Danforth]

based on your other posts, your motor is a 1986

the intake you have posted is for vortec heads and WILL NOT work on your motor unless you change to vortec heads

no issue with back pressure with exhaust/alpha until you get up to a big block (then you run a tube vs a bellows). so with a V6, you cant possibly get enough RPMs to worry about back pressure.

if you have a 1986 motor and go thru the trouble of removing the 2 bbl intake and carb and going to a 4bbl, you at best will pick up 15hp.

your best bang for the buck is a set of vortec heads, a different cam, etc. however that would most likely mean that your 33 year old motor will need a rebuild to justify spending the money.

or enjoy your boat, sell it in a few years and buy the boat you want.

 

[Heybuddy]

based on your other posts, your motor is a 1986

the intake you have posted is for vortec heads and WILL NOT work on your motor unless you change to vortec heads

no issue with back pressure with exhaust/alpha until you get up to a big block (then you run a tube vs a bellows). so with a V6, you cant possibly get enough RPMs to worry about back pressure.

if you have a 1986 motor and go thru the trouble of removing the 2 bbl intake and carb and going to a 4bbl, you at best will pick up 15hp.

your best bang for the buck is a set of vortec heads, a different cam, etc. however that would most likely mean that your 33 year old motor will need a rebuild to justify spending the money.

or enjoy your boat, sell it in a few years and buy the boat you want.

Well Scott it seems you may have been my deciding factor! I’m perfectly fine keeping her stock! I just got the girl running finally with little hurt to my wallet so figured I’d upgrade something for a winter project I guess this isn’t it

 

[thumpar]

I don't know that you would notice the power increase but would probably notice the fuel use.

 

[tpenfield]

Sounds like your request for approval of an intake manifold upgrade has been denied. . . at least for now, until other upgrade options are considered.

 

[Heybuddy]

Sounds like your request for approval of an intake manifold upgrade has been denied. . . at least for now, until other upgrade options are considered.

I’ll be happy with what I got it’s my first boat so next boat I’ll buy something bigger

 

[Scott Danforth]

Im a few years into a re-power turned full restoration.....no mater what you do, get the wife's blessing.

 

[Mad Props]

I'd be happy with what you have... As suggested, if you want more power, you want to invest in vortec heads, intake, 4bbl, cam, etc.. but then again, for that, you might be able to do a repower with a donor boat and put in a V8...
Trust me, I've been there and I have the torn down bare vortec heads in my basement from my last boat that I never got around to putting together (big paper weights now)... All that to say, odds are, there are better ways to spend money to enjoy your boat, and spend money you will...
:mad-new:

 

[Heybuddy]

I'd be happy with what you have... As suggested, if you want more power, you want to invest in vortec heads, intake, 4bbl, cam, etc.. but then again, for that, you might be able to do a repower with a donor boat and put in a V8...
Trust me, I've been there and I have the torn down bare vortec heads in my basement from my last boat that I never got around to putting together (big paper weights now)... All that to say, odds are, there are better ways to spend money to enjoy your boat, and spend money you will...
:mad-new:

Mad props I wish I had seen your 2 bbl carb rebuild video before I did mine 2 weeks ago ... went smooth figured it out still