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bjh517
10-26-2003, 02:42 PM
I am getting financially nervous about repowering my 16 with a Vortec 5.7. The 4.3 is working fine, just too slow. Is there anything I can do to squeeze any more power out of my stock Mercruiser carbureted 4.3 and what sort of increases can I expect from them??

Would a new manifold, carb and thru-hull exhaust make a significant difference??

As usual, any advice would be helpful. Thanks in advance.

HyperDonzi
10-26-2003, 02:54 PM
A 4.3 is a 5.7 350 with cylinders 7 and 8 cut off. 350 pistons, rods, etc will fit. Buy Vortec Heads, Manifold, carb and you will be around 220 hp. Thru-Hull alone wont do much besides sound. If you have the cam for an open exhaust, then it will be beneficial.

Tommy

BUIZILLA
10-26-2003, 03:22 PM
Actually, it's not 7 & 8 that left the party, but it was two in the middle of the party. wink Read back on some other topics concerning this, and i'm sure you'll jump right in and fix up that V-6. CrackerJack herein ha a VERY impressive performing V6. I see your from SE F-L-A somewhere'. I'm in Miami as is the rabid dog, so either of us can send you in the right direction for hop-up goodies.
Go for it and juice up that 6 banger. :p

J :cool:

bjh517
10-26-2003, 03:33 PM
BUIZILLA,
Actually I am in Pompano Beach. I would love some local contacts to discuss my situation. How much do you think I would spend to put new heads, carb and manifold? New Cam???

smokediver
10-26-2003, 06:44 PM
what year is your boat ? the vortec heads are hard to beat as is the roller camshaft.. edelbrock is now making a alum. 4bbl manifold for the vortec V6 . Imco also has an aftermarket exhaust.. i dont think the exhaust will give you too much , however , there is a big weight difference..
I am putting on the manifold and 4 bbl.. will let you know how it works ..

bjh517
10-26-2003, 07:54 PM
smokediver,

It's a 1995. Could you give me specific part numbers of the manifold? Or just point me to the web page.

Thanks

MOP
10-27-2003, 08:41 AM
http://edelbrock.com/automotive/

BUIZILLA
10-27-2003, 08:52 AM
BJH, is your boat a 2 bbl carb now or a 4 bbl??

J

smokediver
10-27-2003, 09:17 AM
I think you have pre-vortec heads... look at the bolts on the intake manifold.. the vortec have 4 bolts each side in a row.. edelbrock has been making a pre vortec intake for some time now..summit and jegs both offer it.. it is part #2111 .. that is the edelbrock #. you might wanna give marcdups a shout.. he warmed up his V6.

mikev
10-27-2003, 10:32 AM
i put an edelbrock 4brl and intake on mine and gained 400 rpm this winter doing a gm cam and ported and polished heads. if you have a balance shaft motor I am not sure if there is any performance cams for it.

Woodsy
10-27-2003, 02:35 PM
BJH...

How many hours does your motor have now? You need to a compression test and a leakdown test before you can make any sort of an informed decision about hopping up your existing motor.
Although you are concerned about the cost of swapping for a 350, messing around with your v-6 especially if its tired, will provide minimal gains at best and at worst cost you more money in the long run. Boat motors are constantly under loaded conditions, and this accelerates wear & tear.

By the time you get done swapping heads, cam, intake and adding exhaust you will be well on your way to the cost of a 350 and nowhere near the HP & torque. IF and thats a big if you can get 220HP-250HP out of your V-6, you are still asking alot of a tired motor.

My suggestion is do the tests on your motor and go from there. If your motor has good numbers you can go one of two ways... Sell it and use the cash to offset the costs of purchasing a 350 setup, stock motors are worth alot more $$, or you can decide to hop it up. If the numbers show your motor is tired or borderline, you can leave it alone until you have the money to rebuild or purchase a new motor...


Woodsy

Rootsy
10-27-2003, 06:51 PM
me thinks you could push the 300+ envelope and keep it reasonably tame... of course i'm not talking bout forced induction or extra O2 wink

BUIZILLA
10-27-2003, 07:41 PM
Did we ever find out the 2bbl or 4bbl ??? yet? If the shortblock has 600 hours or less, it's still pretty tight. I don't think 310-325 would be out of the realm. 280-290 is easy.. I don't see any reason that 62-65 mph couldn't be obtained.
First off...buy Stix Magill's SS drive or an equal. wink

J

Rootsy
10-27-2003, 07:44 PM
i think someone's been bitten by the SS bug wink

did i tell ya i know how to make em fit on a GEN II transom assy :D

MOP
10-27-2003, 07:49 PM
Ditto Stix Magills drive cheapest speed gain around and great on a 16, I did a bunch of asking about the SS it is perfect for your boat. Take look at parts for sale section. Jim you do come up with the good ones!

bjh517
10-27-2003, 08:57 PM
Guys, Thanks for the input. It currently has a 2bbl carb. The last owner says it has less than 200 hrs on the engine and my mechanic said the compression was fantastic. I can put my fingers on the numbers tomorrow. Hate to sound ignorant, what is the reference to SS?

Rootsy
10-27-2003, 09:08 PM
SS = alpha SS. the alpha SS is 3 inches shorter than the regular alpha. was only manufactured for 3 or 4 years, 1986 - 1988/89.

this is a unique sterndrive that uses pretty much all alpha innards cept for a few odds and ends.. has a unique driveshaft housing and utilizes a CLE (crescent leading edge) hi-perf gearcase. the SS gearcase is a bit beefier than the outboard gearcases but has the same shape essentially

she really helps settle the 16 hull down and is good for about 6 - 10 mph on the 16 or 18 if setup properly and dialed in... it makes the 16 a whole different beast...

jsut about the best bang for the buck...

this is an SS on my 16...

http://www.donzi.net/photos/jaroot110.jpg

ITTLFLI
10-28-2003, 10:04 AM
I have an SS for sale. It has low hours and is in great shape. I also have the original Merc manual and brochure to go with it!

email me for more info...

Byron
bscholle@intercall.com

Barry Phillips
10-30-2003, 06:44 PM
I agree with Woodsy, in the long run it might be less exspensive converting to a fresh 350 than rodding your V6, which frankly is not worth rodding considering the power gain. You can get the same power out of a stock 350 than a stressed V6, which well be more reliable. If the V6 is tired, better yet. Keep the power below 300 and your Alfa should be fine.

SO-SLO

Rootsy
10-30-2003, 07:43 PM
BJH,

How much do you want to spend on upgrades or repowering? that is where you have to start... that and have a performance goal in mind...

this information will get you on your way to formulating the most cost efficient and benificial plan.

I am all about doing it right AND doing it economically...

MOP
10-30-2003, 09:40 PM
Rootsy how do you get anything done! You must spend a lot of time being eloquent with your thoughts! I think for now our V6 Buddy should follow the SS path and maybe do the 350 when bucks are a tad looser!

My 2-1/2 cents!

MOP