is this boat over propped

[180shabah]

Re: is this boat over propped

and see how many turns i get to one revolution of the engine

OR, how many revolution of the engine to one turn of the prop...

 

[hwsiii]

Re: is this boat over propped

Shabah, theoretically the prop will turn either 1.32 times or 1.5 times for each turn of the engine. LOL I don't make an error unless I breathe.


H

 

[180shabah]

Re: is this boat over propped

Actually it is the other way around. 1.3-2 engine revolutions for a single prop revolution.

 

[hwsiii]

Re: is this boat over propped

LMAOOOO Shabah I TOLD you I only messup when I am breathing. You are 100% RIGHT, thank you. MAJOR CRS


H

 

[180shabah]

Re: is this boat over propped

Ahhh, take a deep breath

 

[jaxnjil]

Re: is this boat over propped

hi guys thats for all the info
i will pull the spark plugs out at the weekend and see how many turns i get to one revolution of the engine , until then thanks to you all
ps the speed is gps but its exactly the same as the air intake speedo on the dash .

it might be easier to do 3 full engine revolutions and that should give you 2 perfect prop shaft rev. if is 1.5:1 which it should be

1.32:1 will go past 2 full revolution

the difference will be easier to see than trying to guess the how far the prop shaft turns for one rev of the motor

 

[recoil]

Re: is this boat over propped

hi guys , might have found the problem why we have no bottom end grunt , it turns out the brother picked the wrong manifold the one that's on is a torka 2 edelbrock but the rev range is 3000 to 8000 rpm , so we intend on swapping the manifold to a performer rpm edelbrock , were its rated at idle to 5000 rpm this might give use the bottom end grunt were after , also having the engine dyno tested to see exactly what hp its producing ,

 

[hwsiii]

Re: is this boat over propped

That makes excellent sense and please let us know the results.


H

 

[180shabah]

Re: is this boat over propped

Performer or Performer RPM????

 

[recoil]

Re: is this boat over propped

now this is were i get a little lost , i think its the performer rpm , there also the reformer air flow , and just the performer , i think the one we want is the performer rpm , if any of you guys suggest any thing else i would consider it , also will we have to do some work on the carb its a quadrajet , or is there a better marine carb on the market , cheers guys

 

[Apollo75]

Re: is this boat over propped

Hello;

From what I have read your boat is over propped. Your set-up is for high rpm horsepower and should turn a higher rpm under load.

Also, that manifold with the ported heads and cam? Marine --- what size? All of these will lower your low end torque, and torque is what launches a car or boat. Too bad you can't put a low stall torque converter in the boat

I would change the manifold to a lower rpm two plane design for low rpm torque and depending on the cam may have to advance the cam a couple of degrees. I think the increased compression from installing flat top pistons should make up for a lot in gearing, etc.

"Advancing the camshaft means that you are starting the opening and closing process sooner in the cycle. It generally improves low-speed torque and mid-range power while sacrificing top-end hp. "

www.carcraft.com/techarticles/116_0403_camshaft_basic/index.html

When you get the rpms correct and the low end torque you need --- consider playing with the carb. There are two sizes of Q_Jets 650 and 800 cfm. There is also many tricks to help those carbs perform great.

OFM