fbeard

i have a g26 with a mild to meduim mod on engine, a walbro 813a carb,custom prop from dasbota i think it is a 6717 3 blade,and a racing exhaustfrom bonzi sports.i can only get about 40mph out of it what else can i do to make it faster?

Dan S

what is the length of your pipe, measured from the exhaust port, around the header and to the center of the band?

Dan.

mymammushouse

using stock exhaust off the fuji engine or did u upgrade?

fbeard

16 1/2 inches the exhaust is from bonzi sports.the header pipe is custom from bopnzi and is shaped like the factory

Dan S

16 1/2 inches !!!!

your not giving me the length of the tune pipe are you?

if that is the length from center of exhaust port, following the header up to the center of the 1" band, its too long.

did you cut the header or are you using it the full length it came as?

not sure if a mono is the same as a Cat or Hydro when it come's to the pipe, but I would think that a good start would be 13 inches.
hopefully someone else will chime in.

Dan.

fbeard

i really dont know how to measure it i know center of the band but the header make 2 bends in it.

WakeBoardnBash

Using a string to follow the bends in the header and then transferring the string onto a measuring tape never crossed your mind?




LMAO!
Wow....

Dan S

a wrap to center header is not the best thing for performance.

Dan.

Dreamin Hemi

mymammushouse

is this the exaust system??
http://bonzisports.com/catalogue/pro...roducts_id=284
or
http://bonzisports.com/catalogue/pro...roducts_id=288

Bbbutch

As the guys above have indicated "you need to get your exhaust tuned correctly" and that is one of the very first things you do to get the motor to run at it's maximum efficiency.
Most everybody starts by measuring it out. I believe it’s 12 ½� to the largest part of the first cone on the pipe. I’m sure I’ll be corrected if that is wrong. Then I make ¼� marks on the header and move the pipe in and out until I find the “sweet spot� for a combination of maximum speed and best launch out of the corners (I use an onboard GPS unit for the speed).
After you get that right come back and we’ll give more things to try. A lot more!
With what I perceive as your present set up I would think your boat could hit high 40’s MPH with the proper tuning of the motor and hull.

wildman51

Im new at this but I think that prop has to much pitch 113.9 thats alot for these little motors try a 72mmx105 dia maybe your motor cant unwind these motors turn 14000 rpms dont hold it back let it unload hope this helps .wild

Dan S

a 6717/3 for a mid mod may be too much prop.

a 7016/2 could be much better.

Scott,
I believe most people measure to the center of the band, but there is more than one way to skin a cat.

Dan.

fbeard

well the prop came from dasboata it is reduced and all the good stuff.that is what he recommended.as for exhaust i have the racing exhaust from bonzi with the same style header as factory.

fbeard

ok my ehaust measures 16 1/2 inches full length to cooling ring.i can only cut 1 3/4 inches off thge header would that make a big differance

fbeard

i also have a 65 /100 stock prop and a 67/105 3 blade grim racer sapeed prop are thes close

Bbbutch

The Grim Racer 67/105-3 prop is a good prop for a mid range modded Zen motor.
I've always gotten more speed out of a three blade prop "on my Rio" than a two blade by about 8 MPH. But I do know that two blade props work very well on many other boats.
If your motor can turn it try an ABS 2814-3.
ALSO! I've had three Grim Racer 67/105-3 props and not one was close to being balanced out of the box.

Dan S

fbeard,
I know who Dasboata is and I know he make's great props, but you can have the best prop guru make a prop for you and if the pipe is not correct it will not perform like it should.

you need to play with your pipe length, if I remember correctly making the pipe shorter gives you RPM and making the pipe longer, more torque.

before you cut your header start playing with the pipe.
Look at the pic, go in as far as the line or go out but not pass the O rings.

take the boat for a test drive and see what you get for performance, if you need to go shorter because it gets faster that way, than yes you will have to cut the header.
another good thing would be to get a spare header and even maybe get a 90 degree header instead (you will have to re think the setup).

Dan.

kb guy

rio/ full mod zen owner. if you want to get full benefit from your engine, ditch the deep v header. you`ll never get it short enough. i`m using hanson # 14 header and zero band pipe. see my reply to your post on other gas forum.

CARTER

fbeard

ok i cut off 2 inches and remounted the exhaust.ill run tomarrow and tell you all how it runs.

fbeard

ok ran baot last night did not get any gaines off the props i had a friend let me us a perather prop and wow i gained big time.it was a 2 bladed prop i forgot the numbers i think it was a 670 or 674 .so now im ordering new props.thanks for all the help

wildman51

just try different props as each prop will need different tuning its not the pipe thats fine tuning after you get her runnin hard the pipes and headers are minute tuning like leaning dont over look the obvieous ...bad spelling sorry put the pipe and header on run it make the engine happy then fine tune the ole girl the reward will be worth it