Mods for Merc 4.3L MPFI?

[kyle f]

Re: Mods for Merc 4.3L MPFI?

Wow, thanks for all the info guys.

I guess, short and to the point... you can't do anything, just doesn't float with me. There are things that can be done, the question is how much will it help. I will agree that 5hp won't do much in the water, but sometimes its just nice to have some personal touches (mods) on your boat.

I think since most of my time on the boat is spent pulling people and taking short trips from Marina to Marina on Norris Lake I am goign to try to build to suit.

I am going to try the Whaletail as its only $30, easy to install and just as easy to take off if it proves to not be a good combination on my hull. I can re-coup the cost pretty easy at my marina as a lot of guys swear by them.

I am also certain that I will be adding the trim tabs over the winter for next season. I can't find anyoen that has anythign bad to say about them.

As for the prop, I think I need to find a prop shop locally that will let me try a few out. I think I need to put a 4blade on with a slightly higher pitch and see if I can gain anything up top form the higher pitch and keep the nice low end with the trim tabs and the additional blade instead of just making a trade off. I would like to get the slight increas in fuel economy from a higher pitch without sacraficing the pull out of the hole, and I think the trim tabs will help with that by getting me on plane quicker.

 

[QC]

Re: Mods for Merc 4.3L MPFI?

One last plea . . . forget the tale if you are looking for top speed. If you want to spend some money and "personalize" it go with adjustable tabs like Bennett's or some of these:

You could try thru transom exhaust. Get any weight you can out of that thing and what you have to have keep aft. The Tabs will help if she porpoises from the weight shift and you will be able to get the bow further up. The Hydro whale fart thing will only be mo stuff in da water and there is not one piece of independent test data that show they will help with top speed on a boat like yours. You are looking for 2 or 3 MPH and the tale will cost you that easy. Remember you can get the tabs out of the water, you can keep from adding one blade in the water, you can get the bow further out of the water, but the tale can't get out of the water and when you take it off you have holes in your AV plate . . .

When I see a nice Mustang with good stuff and nice wheels, I say to myself "awesome". When I see a boat with a tale I say "M-I-C-K-E-Y M-O-U-S-E". You can definitely squeeze a couple of MPH out of her with setup stuff, perfect prop match etc. Blowers work too, but you'll be hard pressed to find stuff for the 4.3 that is marinised. The big HP guys are looking for 800, not 250 as they can get that from a stock, carbed, small block.

 

[Tail_Gunner]

Re: Mods for Merc 4.3L MPFI?

Him and his damm alway's have to have a finger on the button ideal...


Now here's the real thing my fellow boater Nauti-John's fully active trim tab's such a simple and elegant solution they are....

As Qc say's Whale tail's are a thing of the past and actually hinder performance, go to the prop forum's and find out what pitch of prop would work best for you boat and state you goal is overall speed. Im quite sure you will end up with a Merc Enteria, but that's another adventure...

 

[QC]

Re: Mods for Merc 4.3L MPFI?

Him and his damm alway's have to have a finger on the button ideal...

Yup. Me and Dubya, two peas in a pod . . .

 

[180shabah]

Re: Mods for Merc 4.3L MPFI?

...And just to show that we'll challenge anything even from guys that have been around . . . even guys from the home of the best brothers in NASCAR.

That's simply not true. 100% the opposite in a marine application. That's why Marine manufacturers rarely even note torque numbers. Increased peak torque will help hole shot, and more torque at higher revs will raise horsepower, but you need 'em mo ponies to make 'em go fasta . . . I think the rule of thumb between 50 and 60 is $1K per 1 MPH. It gets worse from there . . .

Sorry I guess I oversimlpified a bit. I just hate when people get hung up on HP, it is a derived number (torque x RPM.......) Most things that we do to increase HP like increase revs(bad for an outdrive BTW) or swap cams to shift the powerband up a little higher, we do at the expense of low end torque. How BAD *****, is he gonna look goin' 52 when during the 20-30 seconds it took to get on plane some joker in a ponton boat with 125 on back has already made it halfway across the lake? I absolutely agree that it takes HP(high RPM torque) to run high speeds, but it seems as though kyle is willing to do anything to get a few more of those top end ponies(it works on a car, so it must work in a boat witha car engine). I was just trying to overemphasize(sp?) the importance of keeping the whole package in check.


KYLE - if you switch from a 3 blade 19" prop to 4 blade 20-21" prop you will LOSE 600-900 RPM at WOT as well as losing several MPH. You do not have the power to spin it. You will lug the engine, and eventually you will tulip a valve or two or three...

 

[QC]

Re: Mods for Merc 4.3L MPFI?

No prah, 180shabah, as I have the opposite pet peeve which is that the automotive guys have emphasised torque so much that people are starting to think horsepower doesn't matter. I often use the example of a guy torquing big main cap bolts on a truck engine to 300 lb/ft. A human can do that, but he can't move a car very fast . . .

 

[Tail_Gunner]

Re: Mods for Merc 4.3L MPFI?

Sorry I guess I oversimlpified a bit. I just hate when people get hung up on HP, it is a derived number (torque x RPM.......) Most things that we do to increase HP like increase revs(bad for an outdrive BTW) or swap cams to shift the powerband up a little higher, we do at the expense of low end torque. How BAD *****, is he gonna look goin' 52 when during the 20-30 seconds it took to get on plane some joker in a ponton boat with 125 on back has already made it halfway across the lake? I absolutely agree that it takes HP(high RPM torque) to run high speeds, but it seems as though kyle is willing to do anything to get a few more of those top end ponies(it works on a car, so it must work in a boat witha car engine). I was just trying to overemphasize(sp?) the importance of keeping the whole package in check.


KYLE - if you switch from a 3 blade 19" prop to 4 blade 20-21" prop you will LOSE 600-900 RPM at WOT as well as losing several MPH. You do not have the power to spin it. You will lug the engine, and eventually you will tulip a valve or two or three...

Naw not that much, the boat is only 2800 lbs and has a 19 degree v with a merc leg, gear's are probably 1.84, truly a guess here but a good stilleto 20pitch 4 blade would net him out @ probably 4800-4900 turning 52 and maybe a Merc Enteria would come in 21 maybe 22 and get him 53-54........two inches of pitch wont shut him down 600 rpm or more...

 

[moser42]

Re: Mods for Merc 4.3L MPFI?

How much hp would a 4.3 carb 2brl(190hp) gain with a 4brl?
and how much would a 4brl cost roughly? can you just take off the 2 brl and bolt on the 4 brl and go?

Thankss!

 

[kyle f]

Re: Mods for Merc 4.3L MPFI?

Possibly, not much going to the 4BBL. IT all depends on how much CFM the engine needs. A carb likes good vacuum to give a good air/fuel mixture (atomization) for a good complete burn.

You first need to see how man CFM your stock carb is rated at and see what is available in the 4BBL that will fit. Most SB Ford and Chevy's in street cars, mildly built for driveability and performance (300-350hp range) only need a 600-650CFM carb. Your 4.3 won't need that much at all. Probably only around 500CFM to run well.

 

[moser42]

Re: Mods for Merc 4.3L MPFI?

Sorry I know this might sound dumb but whats CFM? how do I know how much the engine needs and how much my stock carb is rated at???
It is a '06 4.3L carb if that helps any.
So maybe a 5-10hp gain with 4brl? If its only 5 or 10 hp its not worth it.
how much $$ for a 4 brl??

 

[180shabah]

Re: Mods for Merc 4.3L MPFI?

Like mentioned above CFM(Cubic Feet per Minute) is CFM. just switching carbs will net little if any. The difference is in the intake manifold. realisticly, you can expect 215-220 out of a Vortec 4.3 with a good intake and no internal mods. I would guess that an adapter plate and your existing 2bbl carb would be about the same, but I don't know anybody who has done it, so I can't say for sure. An Edelbrock performer (I believe it is the 1409) is a 600CFM 4bbl and can be tuned for the 4.3, they sell a kit just for this engine. I have a Weber clone(and so does Bond-o), I doubt that you will ever hear either one of us recomend a different carb. They are just to simple and reliable.

240hp(ish) is possible with a cam upgrade but this is about the limit in marine use. Also, before you through money out on a cam, discuss it with the manufacturer and make sure it is good for marine use. All power should be made under 5k and LSA(Lobe Seperation Angle) should be 109-112deg to avoid inversion.

 

[180shabah]

Re: Mods for Merc 4.3L MPFI?

Sorry I know this might sound dumb but whats CFM? how do I know how much the engine needs and how much my stock carb is rated at???

At 100% Volumetric Efficiency your 4.3L would only move 379 CFM(Cubic Feet per Minute)

The Merc 2bbl is rated at 500CFM(I think, but don't know)

Looking in the Summit catalog I got the following prices.

1409 Marine 600CFM carb $320
2114 Satin finish Intake Manifold $240

Shop ebay though and youe can find the carb or one of the Webers for $100 or so. Add $50 for a rebuild kit and you got one for half price. Bottom line, you are looking at $500-700 for 25-30hp. You gotta decide if it is worth it.

 

[Bondo]

Re: Mods for Merc 4.3L MPFI?

You gotta decide if it is worth it.

Ayuh,.........

I Do....... It's Noticable.......

And,.....
When you've got the 4bbl,......
The MPI is what you Wish for........

 

[180shabah]

Re: Mods for Merc 4.3L MPFI?

Or those of us with the "old" engines, there is the constant lust for VORTEC.

But even with 175hp I can run 52 (at 5000)when it is just me and a 1/4 tank of gas. This is with a 21" hustler AND a slight hook in the hull. Six years sitting on jack stands without moving has left it's mark. I can't wait to see how she runs next spring with a clean running surface. And maybe a set of vortecs

 

[smokediver]

Re: Mods for Merc 4.3L MPFI?

i would keep the mpi and enjoy the ride ! i had a donzi 16 classic and it came with a vortec v-6 2bbl.190 horse motor ... solid 55 mph boat ... i then switched to a performer intake and a 4bbl gained 3 mph .. 4 on a good day ... i pulled the motor , moved the front mounts and went to a 5.7 merc motor .. big mistake .. not the engine swap .. the brand ... it tanked a month out of warranty ... pulling it apart , it was not even built to a decent car engine spec's . even had steel freeze plugs ! so i then bought a 383 stroker , 430 horse and took the accy's off the mercjunk and then ... i had a mover !! the ratio in the drive was switched , from the 1.84 to the hd 1.47 ... 73mph boat at that point ... but i had a lot more fun with the turn key 4.3 .... lot less headaches !!! the 4.3 can be made to bring 300 reliable horses .. with a little head work , port matched manifold , cam ... having been there and done that don't waste your money ... buy the boat you want that has the power already in place .. as far as marine versus car ...there is no magic in a marine motor !!! the ring gap is a little different and the cam has tighter lobes and closer duration ... that is it !!!! hope this helps

 

[micel]

Re: Mods for Merc 4.3L MPFI?

Basically any marine engine performance adders are quite costly,plus the rig is going to take a big hit in dependability!Unless you got alot of extra money to blow and do not mind boat being broken all the time just leave the boat stock and enjoy it and spend the extra money on next hobby.