prop selection

[k&b guy]

have 32" racing tunnel w/ stock 7.5 k&b. (8701). bought used app. 15 yrs. ago. came w/ p235. looking for better prop choices. i`m sure prop design has come a long way since then. tnx. CARTER

 

[shoboat]

Carter,

A lot of choices for that kind of set up. 1450 B/C,H-7 B/C,X-447,X-448,230,225,all can work well depending on your set up.

A 235 seems a little big to me for good RPM.

Have Fun,

Mark Sholund

 

[Dan Hydro]

I agree with Mark,

when I had my 7.5 I used 2 props, a P225C and P230S.

Dan

 

[k&b guy]

thanks guys. CARTER

 

[Dan Hydro]

Carter,

the 7.5cc (8701) is the same as my old one, if you want to gain in performance, upgrade your carb to a more recent version like the 8702/8703.

The bore on the carbs are bigger and it made a good difference on my old 8701.

The next thing would be to upgrade all 15mm ( rod, crank, case etc) to the 17mm, thats what most of the newer 8702/8703 version came with, that aswell makes a huge difference.

Dan.

 

[k&b guy]

thanks for the tips, dan. right now it`s stock, except for somebody hogging out the 4 exhaust holes. louder than hell!!!!. CARTER

 

[VansRacing]

thanks for the tips, dan. right now it`s stock, except for somebody hogging out the 4 exhaust holes. louder than hell!!!!. CARTER

A note of caution:

The holes in the lower unit creates back pressure and provides fuel tank pressure to help with fuel delivery. This pressure is already borderline. If the holes are drilled too large, it can cause you to have a narrow available needle situation. If this is the case, you may be replacing some parts real soon.

My advise would be, be on the safe side and get a new lowerunit.

-Carl,

 

[k&b guy]

thanks for the tips, dan. right now it`s stock, except for somebody hogging out the 4 exhaust holes. louder than hell!!!!. CARTER

A note of caution:

The holes in the lower unit creates back pressure and provides fuel tank pressure to help with fuel delivery. This pressure is already borderline. If the holes are drilled too large, it can cause you to have a narrow available needle situation. If this is the case, you may be replacing some parts real soon.

My advise would be, be on the safe side and get a new lowerunit.

-Carl,

swapped out 235 for 225. 230 no longer available. stages easily. no cavitation.want to try something close to a 230. looking at the x646 & x648. are the prathers progressive, like the x series, or am i comparing apples to oranges? the diam. & pitch are close. need some help here. CARTER

 

[Duck899]

One of the guys here is running your exact set-up with an X-450/2. Get the engine at the right height and it will give you good performance.

An X- 646/2, 648/2,448/2, 450/2, P-225 are all very similar in performance but have different cornering properties....you just have to experiment with balance point and your driving style, etc.....

I run a CMD 1445/2 cupped to 3.6" on my Leecraft with the stock K&B pro and it goes ok.....

A 1445/2 cupped at 3.1"- 3.3" also works good on your set-up.

Going out with others who have lots of props you can try is the best way unless you want to invest hundreds of $$$$$ in props.....

Cheers

 

[k&b guy]

One of the guys here is running your exact set-up with an X-450/2. Get the engine at the right height and it will give you good performance.An X- 646/2, 648/2,448/2, 450/2, P-225 are all very similar in performance but have different cornering properties....you just have to experiment with balance point and your driving style, etc.....

I run a CMD 1445/2 cupped to 3.6" on my Leecraft with the stock K&B pro and it goes ok.....

A 1445/2 cupped at 3.1"- 3.3" also works good on your set-up.

Going out with others who have lots of props you can try is the best way unless you want to invest hundreds of $$$$$ in props.....

Cheers

thanks rob. CARTER

 

[ozbryan]

Hey dood im still running in my engine but im useing the x447 and this thing looks like its going to scream!