40 Parabolic

[gooycheese]

Hi All,

I have got a CMB45HR in a 40 Hawk with a 1457 prop. I am interested in finding out a good place to start with pipe length. I know some have there pipe at 9" and others are like 9 3/4". The reason I ask is I don't wanna cut the pipe, I wanna cut the header but I don't wanna cut to much. I have been running the AB45XT standard muffling pipe, but measuring that was always a issue since everyone measured it a different spots.

Please Help,

Thank You

Paul

 

[Ron Jefferson]

Paul,

I have no experience with the CMB HR motor, but I run that pipe at 8 1/2" on a picco blackhead. I think I'd start at 9 1/2" and cut 1/4 inch at a time.

Good luck, Ron

 

[Stuart Barr]

Hi All,

I have got a CMB45HR in a 40 Hawk with a 1457 prop. I am interested in finding out a good place to start with pipe length. I know some have there pipe at 9" and others are like 9 3/4". The reason I ask is I don't wanna cut the pipe, I wanna cut the header but I don't wanna cut to much. I have been running the AB45XT standard muffling pipe, but measuring that was always a issue since everyone measured it a different spots.

Please Help,

Thank You

Paul

Paul,

I have been running that pipe at 8 3/4". Start at 9 1/4" and plan to shorten if your boat will carry it. Great pipe.

Stu

 

[LarryConrad]

I run mine at 9.5 on a MAC in a Eagle SG. It will pull a 1655, runs real well with a 1457. Should be a real screamer when I get my sleeve and new piston back from Brad Christy.

 

[aaron alberico]

Start at 9-1/4 and work your way down,

i run around 8-1/4

regards Aaron

 

[shoboat]

Paul,

8.5" should work real well with that pipe.

I would watch how much cup you put in that propeller though.

Another good pipe is a 67 OPS pipe at 8.5" also with a prather

muffler on the end. Most are running their pipes too long for

real good RPM, and they wonder why they are not going faster. You do not

need a lot of propeller to go fast, a good start would be 4.09" to

4.29" max on that set up. Richen up that needle with a shorter pipe length.

Remember: RPM = SPEED

Good Luck Testing,

Mark Sholund

 

[LarryConrad]

I run mine at 9.5 because 1.I'm running a tired MAC 2. It is the length that Andy Brown recomended.. 3. I have a old heavy boat...compared to the current Crapshooters. 4.It launches easy throttles well and pulls the props I have tried on it well, 1457@ 4.5" cup, and a 1655@ 4.5" cup With a fresh motor I may be able to go shorter on the pipe. Every boat is different and everybodys set up skills very widely. I could probably run the pipe much shorter with a CMB RS...If it will fit in my boat.

 

[shoboat]

Larry,

With that much cup I doubt you will be able to go much shorter.

You should back down the cup a little more to shorten the pipe

more.

Good Luck Testing,

Mark Sholund

 

[LarryConrad]

Larry,

With that much cup I doubt you will be able to go much shorter.

You should back down the cup a little more to shorten the pipe

more.

Good Luck Testing,

Mark Sholund

I'll give it a try, right now it's just sittin' on the shelf till I get my sleeve and new piston back.