I want to go FASTER !

[oops!]

this is a loaded question so ill try to keep it about the motor/drive.

im running a 68 sea ray 19 foot closed bow (src 190). approx 2500 lbs dry. 3500 loaded.
4.3 merc 2bbl. (normally asperated obviously)/ an alpha 1 w/19inch 3 blade alum.
dont know what kind of prop or the width. 4600 WOT= 44 mph.

id like to do a respectable 55-60 WOT. however still want to pull a skier and get good gas milage to boot. relyability is key.

I know, I want my cake and eat it too.

I am toatally refitting the boat. motor comes out on the weekend.

is there anything i can do easly and relyably to increase the speed?
at WOT/plaining speed can i just add a roller cam to get the extra rpm?
(at plaining speed you shouldnt need too many more ponies.)
obviously a 4 bbl will go on.
i also intend to use a cold air intake to the carb for max fire in the holes.
stock iginition. (thunderbolt)
i think the the alpha 1 can take 300 hp (dont know the drive gear ratio) so i should be ok with it.

the hull is being refit and im not afarid of mods to it to get a little more top end. any suggestions on hull design would also be appreaceated.


P.S sorry for so many indivuidual subjects. i didnt want to cross post and you need to see the full picture before accurate answers can be givin. this was the only forum that i could think that would fit.

cheers and thanks

oops

 

[Bondo]

Re: I want to go FASTER !

Ayuh,......... All that should get you into the High-40s.......

Drop in a 350,+ you'll probably see the low to Mid-50s..........

You'd probably need 3 Times your present power to even get a Glimpse of 60mph........

 

[ron7000]

Re: I want to go FASTER !

you want to go 55-60mph on a 1968 boat with a v-6 4.3L engine, are you mental? uh yeah you need some more ponies, look at any boat 1990 or later that's 19' that does 50+mph, they sure as hell don't run a v-6.
As for hull mods, mod the thing into the 21st century by buying a new boat with a 5.7L engine.

 

[tommays]

Re: I want to go FASTER !

I think you will find while it is a FINE boat(really sturdy) there have been a lot of design changes that allow new Hull designs to get more speed out of the same HP



Tommays

 

[MikDee]

Re: I want to go FASTER !

A healthy small block 350 might get you to 55, but to get 60, you'd need either a 383 worked, or a big block Chevy. Usually the limit on a 4.3 is about 50, or low 50's

 

[blouderback]

Re: I want to go FASTER !

Yeah, it's not the power you need to worry about, it's the hull design.

 

[wire2]

Re: I want to go FASTER !

Boat speed is a bit like drag race times; 10% more power will get you from 16 seconds to 15, but you need 50% more power to get from 10 to 9 seconds.

 

[oops!]

Re: I want to go FASTER !

yup thats what i thought.
need at least a 350.

the reason im keeping the hull is I LOVE THAT BOAT!
sturdy const, beauteful lines, in my humble opinion, a classic!

any good hull threads, or forums?

hey mods! this a fantastic site!
you guys are really up on your stuff.
any chance of adding a hull design forum?

thanks
any other ideas or suggestions, please keep them coming!

oops

BTW, oops stands for the fact that i fell in love with my old used boat!

 

[jimmbo]

Re: I want to go FASTER !

Perhaps lowering the compression a couple of points and adding a supercharger could boost your power enough. Not an easy mod for first timers though.

I have a 18 1/2 footer (glastron 195 sx) with a 5.7 VP. When running light with the 4bbl carb it will hit 65 - 66 mph, with the factory 2bbl, 59 - 61 mph.

 

[whywhyzed]

Re: I want to go FASTER !

My 67 Grew/Slickcraft did 53.5 mph on a cool night this summer....and it's a 1960's hull design. It has a 3.8L V6 with a quadrajet.
Mind you, it's a 17.5 foot boat...not 19 foot.

The truly unattainable goal here is fuel economy.

My spring project is a larger fuel tank.

 

[HT32BSX115]

Re: I want to go FASTER !

If you want to go faster, get a different boat. You'll spend a lot of money trying to do it with slightly larger engines.

You could probably do it with a 454 or 502....but you might break that Alpha if you "straight-arm" throttle or run it at WOT a lot.

My 21' Four Winns does about 58mph with the 330hp 454/Bravo III. (1.81:1 ratio, 26p props, 4600 rpm) It did about the same with a 340hp OMC 460 King Kobra (1.41:1, 20p prop, 5000 rpm).

To find ball-park figures go here: --->http://www.go-fast.com/Prop_Slip_Calculator.htm[/url]

for a single prop 11-15% slip is normal....for a duo prop 6-8%


Good luck!



Rick

 

[oops!]

Re: I want to go FASTER !

Perhaps lowering the compression a couple of points and adding a supercharger could boost your power enough. Not an easy mod for first timers though.

I have a 18 1/2 footer (glastron 195 sx) with a 5.7 VP. When running light with the 4bbl carb it will hit 65 - 66 mph, with the factory 2bbl, 59 - 61 mph.

hey jimbo! hows my home town? hows my hockey team doin? all i get here is the canucks!

love the blower idea i actually thought about nos. (till i took my head outta my a**)

60 mabe a dream, (like the guys here that know have so eloquantly put it, "are you outta your mind!!! "tee hee)
i think i can get 55 with the right prop and gears tied to a fi 5.7. i just dont want to burn gph! im too cheap at 4.50 a gallon
this 4.3 sipps fuel at 20 mph plaining.

cheers.
oops

 

[oops!]

Re: I want to go FASTER !

good info.
thanks rick
i allways wonderd how to calcluate prop slip

 

[John_S]

Re: I want to go FASTER !

Hull mods: forget it, or go look at some boat builder forums to realize how involved the design, modification, and testing of such work will be. Look at adding some smart tabs, which will probably add some better handling characteristics to your hull, and maybe a 1-2mph wot speed.

What maybe holding your speed down is extra weight. That old of boat, has a good chance of having water logged foam in it. And if that is true, you will probably have enough inside hull work to fret over, you will forget all about changing the outside of it.

4.3L vortec 4brl or 5.7L vortec 4brl. Pick one. Its a gas milage vs top speed question that only you can answer. Both will probably need drive gear change, but you might get by with just prop on 4.3. Make sure you consider that the sb will add about 100lbs to stern and change the attitude of the boat. Review Merc installation manuals: http://www-alt.mercurymarine.com/mnetdata/sisdata/instlcov.pdf and pay attenion to exhaust manifold height. I think '90's links work.

 

[Mischief Managed]

Re: I want to go FASTER !

Assuming your 4.3 is a 190 HP engine, you would need 297 HP to go 55 MPH and 353 HP to hit 60, for the same prop efficiency.

There's a lot of speed to be gained with a better prop and a bit more RPM. I bet you could squeeze at least another 3 MPH out of your current setup with a 17 or 18" SS prop and 4800 RPM. If true, you would then only need 260 HP to hit 55 or 309 HP to hit 60.

If the 4.3 is rated at less than 190 HP, or you are not reaching 190 HP at your current WOT RPM, you would need less power than I specified.

 

[45Auto]

Re: I want to go FASTER !

Here's Stingray's comparisons (6 pages) of 19' with 4.3's.

'http://www.stingrayboats.com/products/performance/CompareManufacturers2.php?temporary=;;;&hp=130-190&enginemake=SD&length=19&initial=1&date=&lengthtype=on&displ=4.3L&fuel=&sort=speed&showstingray=&onetokeep=&dispclicked=1&tocompare=[/url]

Mid 50's with your 4.3 doesn't look unreasonable at all with a modern cam, manifold and 4 bbl.

 

[180shabah]

Re: I want to go FASTER !

Mid 50's with your 4.3 doesn't look unreasonable at all with a modern cam, manifold and 4 bbl.

I gotta agree - I have a 4.3LX(175hp) in my 18'er (weight is about the same as oops's boat - 2600dry) and this memorial day I was running solo with about 1/4 tank of gas and I hit 50. This was with a pretty good hook in the hull, I can't wait till next season to see what a clean running surface, and possibly an upgrade to vortecs(picking them up tomorrow) and edelbrock intake manifold.

 

[TilliamWe]

Re: I want to go FASTER !

GPS confirmed?

 

[180shabah]

Re: I want to go FASTER !

SOG 49.8, I was heading upstream(5050 RPM), no I don't know the current, but I don't feel at all guilty about rounding up, it is probably more than .2mph.
At normal load, 47.5-48 is common, and WOT stays in spec at 4800.

 

[oops!]

Re: I want to go FASTER !

to all posters, thank you for your input!!!!
please keep them coming

What maybe holding your speed down is extra weight. That old of boat, has a good chance of having water logged foam in it.

im sure the boat is water logged. I rescued it out of a farmers feild 8 years ago. im re -fitting the boat compleatly. (including foam & stringers) thats why im not afarid of hull mods. i was even thinking of doing a stepped hull on it.
i know i should buy a newer hull/boat. but i love this old boat.

i have a marine surveyor and a glass shop on retainer for the re-fit. im going to do it myself.

Thats also why im thinking of cold air to the carb. (a lot of work, not sure if its worth the extra weight. 30 lbs)

the motor is used (but well maintained) the drive was purchased from the same boat.

when i purchased the motor/drive the marine shop promised it would push 50. on my boat.
however when i read what you guys have to say about therotical top speed, and actual. (simple mathamatical formula) i realize i would be lucky to hit 50 in optimum conditions.

im now thinking a 5.7 efi. if i sell the 4.3 i could replace it with little cost. 3-4 grand (after the income from the 4.3).

that might, with the proper gears and prop get me to 55 (i hope)

thanks all, im still learning from you

cheers
oops