Just a little more..........

[Chris Craft 21]

I have a solid and very fine running 4 bbl 4.3 rated at 205 hp that cruises my rig at 22/23 knots current/wind depending @ 3400 RPM. Now that is plenty fine performance in a heavy deep v hull but on the ice cream days I would really love to be able to cruise around 25/26. My feeble brain thinks perhaps another 30 HP or so would let me swing enough prop to get me there. Not being even a little interested in a repower is there a magic combination of cam/intake/carb or other relatively simple upgrades that nab me a knot or 3 of cruise speed?

 

[Bondo]

Re: Just a little more..........

I have a solid and very fine running 4 bbl 4.3 rated at 205 hp that cruises my rig at 22/23 knots current/wind depending @ 3400 RPM. Now that is plenty fine performance in a heavy deep v hull but on the ice cream days I would really love to be able to cruise around 25/26. My feeble brain thinks perhaps another 30 HP or so would let me swing enough prop to get me there. Not being even a little interested in a repower is there a magic combination of cam/intake/carb or other relatively simple upgrades that nab me a knot or 3 of cruise speed?

Ayuh,.... Swappin' the heads, 'n intake manifold to a Vortec set up is 'bout the only Up-grade available to that package, 'n it'll come up short of yer expectations....
To get the Full potential from the Vortecs calls for different pistons, 'n machine work to the block...

Droppin' in a 350/ 4bbl, or mpi might do it though....

 

[Don S]

Re: Just a little more..........

I must be missing something, but If you want to go faster, give it some more throttle. Adding HP is not going to increase your speed at that rpm.

If 3400 is your max rpm, then you have a problem that needs fixed, and not by just adding HP. You could have the wrong prop, wrong gear ratio in the drive or engine problem.

 

[62 ROYAL SCOTT]

Re: Just a little more..........

HELL-O I think DON S is right , or Maybe you need to readjust the linkage or cable for your throttle

 

[Tail_Gunner]

Re: Just a little more..........

That would run about 1800 for the cam, springs, rockers, retainers, intake, gaskets little labor on the heads. On a heavy boat not to much difference and as Don has said at 3000 not much at all that is where it starts waking up with a larger cam. The 4.3 is a great motor but induction has alway's been a issue..Ever notice how GM went from 200 to 270 using a supercharger..same motor lesser cam but you have to pressureize to get strong results.

So bolt on a supercharger and Viola you will get more tourqe actually more than your looking for..But it wont be marine certified and probably run 3000 buttoned up.

 

[Chris Craft 21]

Re: Just a little more..........

I must be missing something, but If you want to go faster, give it some more throttle. Adding HP is not going to increase your speed at that rpm.

If 3400 is your max rpm, then you have a problem that needs fixed, and not by just adding HP. You could have the wrong prop, wrong gear ratio in the drive or engine problem.

Oh no she hits wide WOT, 4400 on the button with 80 gals fuel, wife, 2 little boys and xx pounds of tackle, ice and so on. 3400 Just happens to be the max cruise RPM I feel like subjecting it too for any period of time. My thinking was that a little more horsepower/torque would let me swing a prop with more pitch at the same 3400 revs and gain some cruise speed. But it sounds like I need to be content or spend too much money. Thanks guys.

 

[bnicov]

Re: Just a little more..........

The amount of money you'd need to spend to swing different prop would be better used to purchase fuel or upgrade your current boat.

 

[Tail_Gunner]

Re: Just a little more..........

Oh no she hits wide WOT, 4400 on the button with 80 gals fuel, wife, 2 little boys and xx pounds of tackle, ice and so on. 3400 Just happens to be the max cruise RPM I feel like subjecting it too for any period of time. My thinking was that a little more horsepower/torque would let me swing a prop with more pitch at the same 3400 revs and gain some cruise speed. But it sounds like I need to be content or spend too much money. Thanks guys.

4400 is a tad low..On a 205hp 4.3 they run out of air or power around 4800 rpm that again is where they quit breathing. This can be a highly subjective topic but a 4.3 pushing that much weight running might acutally do better geared a bit lower..not in speed but longjevity and economy...They run overly rich as it is..