wanting more power out of 4.3 vortec v6

[uwish]

hi
i have a 90hr from new 4.3 vortec v6 with thunderbolt ignition and it has a merc 2 barrel carb. the year is 1999 of the motor.
the motor goes great and is in a hamilton jet boat driving a hamilton 212 jet unit. i would like sum more power,the boat
currently does 80kms and @ w.o.t and is pulling 4200rpm. im about to put a higher kw blade in unit to stop some of the slippage as i use the boat in river. with the new blade if i just put it in the motor will pull about 3500rpm. so i would like to bring the motor power up a wee bit.im thinking of buying a edelbrock manifold part number 2111 and a new holley 390cfm carb
which i have been told i should get about 30hp increase which i would be happy with. i may do a cam, but late next year im probably goin to sell boat and built a new boat with an ls motor so not to worried about a cam at this stage.

my question to you guys is do you see any problems with this size carb and is there anything i need to watch out for?

thanks for your help

 

[Bondo]

Re: wanting more power out of 4.3 vortec v6

Ayuh,... I'd go with the Edlebrock 600cfm carb, myself...

 

[uwish]

Re: wanting more power out of 4.3 vortec v6

yeah according to holley website and other boat shops(they use a 465cfm purely on price as the 390 is
more expensive) a 600cfm will be way to big as it will prob only rev to 3800-3900 with a four barrel. also
with the 390cfm it should keep a crisp throttle response which id like.
we had a 308cu gm australia v8 (a holden 308), same sort of thing as a 305 chev say, and it had a 600cfm carb on it and it used heaps of gas, we ended up putting a 450cfm and goin smaller in jet size and it went better lost the throttle lag and used about 2/3 the gas the over the 600cfm. im not a fan for putting an
over size carb on and pouring in to much fuel for the sake of it. i could understand maybe a 600cfm in a
car where the revs could be up around 6000rpm but as i said the motor prob wont see 4000rpm with bigger kw blade going in

any other people done what im thinking of?

thanks ben

 

[wca_tim]

Re: wanting more power out of 4.3 vortec v6

You've already been given the best answer to your question: Edelbrock model 1409 600cfm on a performer rpm intake... will make a marked difference in your performance. It's about the best you can get from a 4.3 without it being more cost effective to step up to a v8. set up to get your wot rpms at 4800 rpms. Do a search, a number of us have "been there, done that". Once it was jetted correctly, mine did very well on fuel... after that I wanted more and a v8 was the best option by far... Just my experience

 

[45Auto]

Re: wanting more power out of 4.3 vortec v6

it had a 600cfm carb on it and it used heaps of gas

Correctly jetting the carb will make a huge difference. Only thing controlling the amount of gas that a carb can put into the engine is the pressure differential across the venturis. With the right size jets, the amount of air flow will determine the amount of fuel going into the engine. Properly jetted, equal air flows will deliver equal mixture ratios regardless of carb size.

Why are you only planning to rev it to 3900 RPM? Max power will be about 1000 RPM above that.

 

[fossill]

Re: wanting more power out of 4.3 vortec v6

If you want more power you need a bigger engine. You're wasting time and money otherwise.

 

[uwish]

Re: wanting more power out of 4.3 vortec v6

wca_tim if you read post correct im guessing from other boats with similar set up it will only rev to to
3800-3900rpm max not 4800rpm a 180hp goodwhench(spelling) 4.3 engine using same pump with the blade im
going to put in does 3200rpm @ w.o.t so this is why a 600cfm carb is overkill.

[QUOTEWhy are you only planning to rev it to 3900 RPM? Max power will be about 1000 RPM above that.][/QUOTE]

im not planing on this but that is all the motor will do with a jet unit with the least kw blade they make a 1.8kw which is what i have currently, the motor only does 4200 @ w.o.t with this set up. the new blade going in is a 2.4kw turbo blade which will take rpm away but improve thrust and low end pick up as whats needed in a jet
boat. you guys rev alot higher in prop boats than this motor will ever do in a jet boat we use the torque of a
motor to "higher gear" a prop to suit (to a point).the jet units become inefficient past about 5500rpm anyway, to give you and idea, same hull, same unit with a 500hp l98 engine with a 3.4kw blade will pull 5500rpm max

if people want to see unit and pump curves have a look at www.hamiltonjet.co.nz

 

[45Auto]

Re: wanting more power out of 4.3 vortec v6

Scroll down to the bottom page, here's the power curve for a 4.3 marine engine.

http://www.gmpowertrain.com/Libraries/Marine_Engines/Vortec_4_3L_V-6_Marine.sflb.ashx

See how it makes max power (226HP) at about 4900 RPM? The slower you turn it the less power you get.

Did you ever read the Hamilton article from the you referenced

http://www.hamiltonjet.co.nz/includes/files_cms/file/JetTorque 03.pdf

on matching the pump to your engine (page 2), where it says "The jet MUST be matched to the engine's maximum power/RPM"?

Good luck with your boat, hopefully you know what you're doing. But if Hamilton and the rest of the world is right, going to a bigger pump is just going to bog your boat down even further .....

 

[uwish]

Re: wanting more power out of 4.3 vortec v6

http://www.hamiltonjet.co.nz/includes/files_cms/file/212 Sales Brochure 2009.pdf

thats what you need to read not an article from 1994 on a jet unit for ships
i assumed you would search site for " hj212" info sorry

what my original question is/was the motor is going to have this blade and it will prob only rev to say 3800-3900 rpm @w.o.t max so with these revs taken into account a 390-465cfm carb would be correct size?

also id say my motor is only 190hp (being a 2 barrel merc carb) and i was hopping for 220hp with better flowing manifold and four barrel?
the only way im going to get motor to turn faster is more power at this stage hence going to buy carb ect?
ideally the motor is not matched to unit 100% but im stuck with what i have for the moment
also going by chart in above brochure im doin the blade that hamiltons suggest so you should get your info right before say you and rest of world know better!
the marine shop that sells boats with these motors and units only do a 465cfm on these motors because they are cheaper than 390 but if the customer wants the best and not worried about $$$ they put a 390cfm on.
edelbrock(after a few emails) say that there carbs are not suitable(i.e to big) plus getting them in my country is a no go, holley recomend the 390cfm as best for the job so you and you 600cfm are way of the mark!

all i was after on this forum was some "real world experience" from someone who had done this size,
not a mate of a mates dog's owner said this?

 

[wca_tim]

Re: wanting more power out of 4.3 vortec v6

the 220 horsepower will be around 4800-4900 rpms... that's why I said to target that. for max speed you want rpm at wide open throttle right at the rpm for peak horsepower.

You can go with a 390 cfm carb and , but experience tells me the boat will be a lot faster with a 600 and a blade that will let you hit the engine's powerband...

to your direct question: the carb may be right for that displacement and those rpms, but the rest of your engine design is not. With those revs, valve sizes are wrong, heads, ports, intake manifold, exhaust configuration, CAM etc... are all wrong, bottom line is that your engine is designed to run at 4800-5000 rpms... running it that far below it's designed operation range and under a heavy load will not only make it a dog, but will shorten it's life considerably...

to put in perspective, theoretically a 600 or 650 cfm carb should be adequate for my 383, but after running 3 or 4 different carbs on it, jetting each carefully and going through the exercise or propping correctly, I assure you it runs better throughout the rpm range and runs a good bit faster on the top end with the a 750+ holley double pumper on it... (worked proform body, quick fuel base, etc...). It also appears to get the best fuel economy with this set-up - better by a good bit then even with the other engine in it...

Sorry if that's not the answer you wanted to hear, but it is the truth as best I know it... and I have had a 4.3 that I upgraded the carb on in my boat... it was running 60 mph with a 4.3 in it - keeping up with a lot of the boats here that have 5.7s in them. I'm not arguiing, just telling you my experience... as are some of the others above, like bondo, 45a, etc... both of whom know what they're talking about... Hope this is helpful. Cheers! Tim

 

[uwish]

Re: wanting more power out of 4.3 vortec v6

they dont make a turbo(which i need) blade combo in less than 2.4kw blade so changing is not an option it is fixed! hence my question IF MOTOR CAN ONLY DO THESE RPM'S AT W.O.T THEN A 390CFM CARB WOULD BE RIGHT?
they may no prop boats but this is obviously not the forum for this question as jets work in a complete differant way. they are not loaded the same as a prop boat for a start and they last just fine in jetboats.
its not a case of if thats the answer i wanted its a case of read ALL the question and then answer if you can
WITH everything i have outlined that is fixed? its no help telling me thats were max power is as with most
jet/engine combos you will never get this anyway.

what im after is the best package with the constraints i have ?

 

[MCL]

Re: wanting more power out of 4.3 vortec v6

If your engine truly is a 99 and vortec,then you need the 2114 manifold.And as recommended the 1409 600cfm carb.Changing the impeller willl only further lower your wot where the engine makes even less power and your boat will go even slower.Going with the suggested combo and using the current impeller might get your engine to its powerband and rev up to 5000 increasing its speed significantly.