More Speed

[Steph_RS]

hi,

I have a 1989 peterborough 18.5' open deck with a rebluit mercruiser 4.3L non-vortec, With a edelbrock performer intake manifold and edelbrock 4 barrel 600cfm Carb, with 1'' spacer, alpha one drive turning a Turning point propellers (express stainless 14-1/4 x 21 pitch) at wot the RPM is about 4700rpm and i'm running 50 mph on the gauge.

I need 2-3 more mph to follow or pass my friend boat. Can you help me to reach my goal ? Do you thing this prop is the best prop for my boat ? Do you have some suggestion ?

Thank you very much that was very apreciated.

 

[Bondo]

Re: More Speed

at wot the RPM is about 4700rpm and i'm running 50 mph on the gauge.

Ayuh,.... That's about All she's got Captain,...

She's done run outa Horsepower....

Are ya trimmin' it up, to the hairy edge of control,..??
How much boat ya got left in the water when runnin' Flat Out,..??

Goin' to Vortec heads, 'n abit of Fine tunin', Might get ya a couple mph.....

 

[etracer68]

Re: More Speed

I agree that you might be at the top of your motors range, theres always more things a person can do, but you may consider puting a scatter shield under the motor. Is the spacer, open or 4 hole? 4 Holes will make the carb draw harder, and pull more fuel. Marine MSD. As always, you can only go as fast as your wallet will let you go. Also sooner or later things brake when your going over stock.

 

[Steph_RS]

Re: More Speed

@Bond-o : yes to hit this speed the trim was up at the maximum and the boat is on the water about 3' and the rest are completly in the air.

@etracer68: I have 1'' edelbrock plastic spacer with 4 holes. This summer i think i will try a 2'' aluminium spacer just for fun. With my old Carb Rochester quadrajet 650 cfm i can hit 4900rpm with 1'' aluminium open spacer .

 

[QC]

Re: More Speed

With my old Carb Rochester quadrajet 650 cfm i can hit 4900rpm with 1'' aluminium open spacer .

That sounds like 3 MPH to me . . . ???

 

[etracer68]

Re: More Speed

I not sure what type lifters are in that motor, but if there not solid, they will start to float soon at high rpms. I drag race, and I know what it takes to keep a motor in one piece, at high rpms. What alot of people dont understand is that rotating assemibly in stock motors are not able to handle alot of high rpms. Sooner or later it will find the weak link, and something will brake in the motor or drive. Just so you understand that if a rod brakes, the block will not stop it from going through the bottom of the boat, and make a big hole, possible fire.

Its always fun to go fast, just be safe, and make sure its safe for the other people too. Im not trying to scare you, but the first time I lost a rod in a motor, it went through the block, broke the starter in half, pushed the header tubes closed, and snaped the idiler arm. Im not sure I would be doing to much hot roding with a boat motor unless i had forged steel crank, and rods, and arp bolts. Outboards (2 strokes) are built to run higher rpms. Chevy 4.3 v6s dont have the best cranks in them.

Good luck, and keep the wet side down

 

[Steph_RS]

Re: More Speed

I not sure what type lifters are in that motor, but if there not solid, they will start to float soon at high rpms. I drag race, and I know what it takes to keep a motor in one piece, at high rpms. What alot of people dont understand is that rotating assemibly in stock motors are not able to handle alot of high rpms. Sooner or later it will find the weak link, and something will brake in the motor or drive. Just so you understand that if a rod brakes, the block will not stop it from going through the bottom of the boat, and make a big hole, possible fire.

Its always fun to go fast, just be safe, and make sure its safe for the other people too. Im not trying to scare you, but the first time I lost a rod in a motor, it went through the block, broke the starter in half, pushed the header tubes closed, and snaped the idiler arm. Im not sure I would be doing to much hot roding with a boat motor unless i had forged steel crank, and rods, and arp bolts. Outboards (2 strokes) are built to run higher rpms. Chevy 4.3 v6s dont have the best cranks in them.

Good luck, and keep the wet side down

Yes i know, this engine is not make to go at high RPM but if i'm able to reach 5000rpm with this setup + little mod/part refresh, i would buy a 23 pitch to drop my wot RPM at 4800RPM (The maximum RPM for my engin.)

Thank you all for your help

 

[Silvertip]

Re: More Speed

Ahhhh -- the old need to stay up with or possibly pass my friends boat! That contest is NEVER won because someone will always show up that is just a tad faster than your friend and then you'll need to keep up with both of them until the point is reached where you either have to buy a new boat, or hurt yourself or your wallet. Tweak the engine all you want but it would be safer and cheaper to just tell your friend slow up a bit and save a bit of fuel in the process. But I do understand the "gotta go faster than him mentality."

 

[Steph_RS]

Re: More Speed

haha!!! i know i know but, the thing is , With a old engine with 800hours on it and a old quadrajet 4 barrels run faster then my rebuilt engine with all new (valve,piston,gasket,valve seat, spring,etc..) and a brand new MSD Fire (coil,wire) and new edelbrock 600cfm marine carb with calibration kit for my engine.

Seriously, i don't upgrage some part just for fun, it's beacause the old part was broke/used and i need to have beter quality part.

For the prop Turning Point Prop Express stainless steel. it is a good brand/design of prop. or it is a cheap one ? Can you think other brand off prop have a beter design more efficiency to reach more speed?

Thank you

p.s. Sorry for my bad english i'm a french canadien

 

[Tail_Gunner]

Re: More Speed

Your at the wall as everyone has said....THe need for speed is not to much...Nice cam new springs...vortech heads polished.... new pushrods....new lifters...1.6....opps and a new intake...about 50-75hp in gain