question on carb bore size

[mark james]

hello alll,

I have been running a speedmaster carb w/ .370 bore on my novarossi .021 L/S.

Will using a smaller bore carb help with top rpm??

Any input will help in my quest for more speed.

thanks

mark

 

[izitbrokeyet?]

Hey Mark,

If you’re using this .37” carb on your L/S outboard, you’ll get better overall performance from a carb that’s between .29” and .34”. That speedmaster carb is an Excellent carb, but I’m thinking it’s better suited for a hydro type application.

just my 2 cents

 

[mark james]

hello izit...

I didnt mention that is in a .21 hydro..

Just wondering if someone has tested the smaller bore carb and what happened .

I have been thinking about getting one of grims adptors and tring a k&b red carb on it (red carb is about .340 bore)

what do you guys thing of that???

mark

 

[shoboat]

Mark,

I good idea on the smaller bore carb.I have tried

many, but I can't tell you the magic number.It will

also depend on your final setup of your engine.

I think if you are in a quest for speed try Rod or

Franko to fix your stock motor.That is as fast as a

stock motor will run in your boat with your setup.

You may also consider a few new props for that

21 hydro.PROPS-4-U has a few in stock that will

make that boat ROCK.

Thanks,

Mark Sholund

 

[TimD]

Altitude also effects what bore size to run.

 

[Mike Nowicki]

Mark

A smaller bore will not give you more top end, but it will allow you to launch more prop and be driveable.

Mike

 

[mark james]

thanks for the feedback guys!!!!!!

mike and mark s you both have mail!!

mark j

 

[Zimmerman]

The smaller bore carb will give better midrange and also make the engine easier to needle, all else being equal.

 

[Propjockey]

Yeah...but who ever won a race with mid-range? ;D

 

[Ian Inverarity]

PJ,

You need an engine to get up to the top end power too! After all, what good would a boat be if it just ploughed along and couldn't get up on pipe!

Nitrocrazed racing: Talk about torque...

 

[Propjockey]

HEY.........LOW BLOW, LOW BLOW!!! LMAO!

 

[Ian Inverarity]

Sorry, couldn't resist.... ;D

Nitrocrazed racing: taking cheap shots....

 

[Zimmerman]

Being able to slow a boat down once in a while without it crapping out has its advantages. In my limited 34 years or R/C boat racing I have consistantly noticed that the fastest boats usually return to the pits via the retrieve boat! >

 

[Slideblues]

Yeah I just did this with my Ackerman mod CMB, Grim's adaptor and a K&B purple carb (bore .340) Real crisp responce and no problemos, Seems like Ed Raz did it too with a gold carb on his Rossi and liked it. Rod G. says that if the throat is too large it will overcome the spray bars ability to keep up and ya start havin problems.

Gene ;D