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[Brigadair]

Hi all


Just wondered what people thought of the best prop and pipe length for a surface drive cat or mono  with a pmc competition pipe (or one of the good Chinese ones).


Reason I ask is that I ran a boat recently with a 29.5-30cm length (from manifold flange to max dia of pipe cone).


This I was advised (and agree) was too short.




Ran  both octura 2 bladed props x470 and x670.
Thanks


Garry

[MPM]

I run 34cm on my 30cc.... Seems to give good HP and plenty of RPM to go along with it.
We tried a short Pipe on the Dyno plenty of RPMs but not as much Hp and torque...
Go longer than 34cm and it produced lots of Hp but the curve was along longer so the RPM build up was alot slower

Its all Trial and Error.

I still think your two short for a 31...

[F1 madness]

Hi garry
does sound to short
My K30 29.5cc likes pipe length around 12 3/4" or just over 32cm and im using the chinese pipe which it seems to run well on
Also make sure you not got too much excess manifold pipe in the pipe itself hehe

[black magic racing]

i run my own tuned 29.5 conquest cat with a very short bonzi pipe and short header,i use a 6717 3 blade prop and to be fair it runs pretty good on this combination.try a different prop,as most of us who have been running cats for years have found out that a good smaller 3 blade works alot better than a larger 2 blade,cats love a bit of lift which is what a 3 blade will give it,,,,just my opinion   

[black magic racing]

another thing to consider is a cat is not pushing a deep v through the water.RPMs is what you want,loading the engine up with a big prop is no good,you want a prop that will let the engine rev out.once the cat is going and set up right it should fly 

[Brigadair]

Many thanks Kurt, Daz and Jack, very much appreciated,




I ran Saturn testing las pt sat with the longer pipe length.


It ran very well.


Whilst I like to test boats a good bit, I won't this time so I'll gamble on on running Saturn at Leicester this Sunday,


Cheers for now guys.


Garry

[Brigadair]

Thanks all for pipe length advice! It cured my teething probs with Saturn and created a few more!!! Lol!!




Time for more testing!!


Briggy.

[craig dickson]

Hi Garry


That longer pipe length paid dividends, I reckon you should be in for a shout next race .....

[tmbc]

Hi Garry


That longer pipe length paid dividends, I reckon you should be in for a shout next race .....

FIGHTING TALK THERE I WILL HAVE TO KEEP MY BEADY OOD EYE'S ON YOU PAIR 

[Brigadair]

Hi all.


Checked three setups with same engines, same pipes (but diff hulls).


Concluded with your good advice, my Saturn pipe length was definitely too short,


Have lengthened it from - approx 29.5 cm to 33cm. My quickest boat is a massive 39cm on a tuned 31cc zen.


Food for thought......




Thank you all for your advice. Much appreciated.

[Brigadair]

Kurt


Are you racing on Sunday?

[black magic racing]

we are hoping to be there this sunday just trying to sort out boats ,looking forward to it

[Brigadair]

Ffffaaaaannnntttttaaaassssttttiiiiicccc!

[craig dickson]

we are hoping to be there this sunday just trying to sort out boats ,looking forward to it

It will be great to see you with us mate


Craig

[F1 madness]

Be good to see ya bud
I know some1 who be glad aswell to see his unc kurt lol

[MPM]

The longer pipe will create more HP.... But having a shorter pipe might create a less hp but will have much more usable rpm with hp.