Where would you prop this motor at?
 

What RPM do you think I need to shoot for with these motors for top speed ? Last year I could run it up to 6000.

I should be running in a few weeks with the new drives , So I need to get a base line on what I have now.

Thanks
Rob:drink:

what kind of boat, drives, weight, gear ratio ?

Looks like they stopped the Dyno at 6000, with the HP still climbing....

Julie

388 Hustler 1.30 gear 30 pt bravo one props turn about 58-5900 last year.B Bax drives ,This year I have there new creasent lowers ,Hoping this might help over a stock bravo foot? I am guessing the boat is 10K running?


Julie it flattens out around 6 rev limiter at 6200.its only gaining 5-8 hp per 100rpm

Just wondering if I went one size larger if it would pull it?



Rob:drink:

How do figure that? If I am at almost max rpm with the 1.30 and 30pt props ,then I went to 1.50 I would run out of rpm with the 30's. A 1.50 gear would prob put me in the mid 6000rpm range.I would need to prop up,guessing 3-4+ pitch sizes .I belive I am with in 1 -2 prop pitch sizes to being right on.


I remember someone telling me once to prop it 1000rpm above peek TQ ,but if the motor is still gaing HP then what?

My TQ was 859 at 3600 and kinda flat thru to 4500 at 858 ,Peek was 868 at 3800

With this motor only gainging 5-8 hp per 100 rpm at the top of the rpm band will it gain speed?

Looks to me like you are right on where you're at or at least very close to perfect. I've heard the 800-1200 rpms past peak torque as well. I think it will depend on how fast the torque is falling off.

Hey Rob,

Looks like HP is flat at 5500 then climbs a little to 6000. If it flattens again to 6 or 7 hp per 100 rpm is time to stop. I think the 5800 - 6000 range is good. Although Slingshots can be very efficiant meaning rpm can create speed.

Your right on with the g.r. change. However a smaller jump down in g.r. and a couple inches of pitch may offer other kinds of rewards.

You can't make generalizations with the "past torque" number. Depends on the motor configurization.

Try what you have to start. More gear case drag could slow you down. Did the X rise. I forgot what you may have told me.

BMax doesent offer a 1.50

I had a stock lower bravo blunt nose, X is the same ,The new B Max gear case looks about the same thickness, the skeg is .400 thick at the torpedo and .250 at the tip. The leading edge is flat:eek:

Heres the Dyno sheet showing the HP

Thanks
Rob:drink:

I may be a bit of a simpleton here, but peak hp is where I thought any boat should be propped for peak speed. Therefore, I think you should shoot for 6k. If your hp is relatively flat to a couple hundred rpm above that, then you could try propping to around 6200 for improved midrange accelleration and holeshot, but you may lose a little top end for spinning the prop so fast. A 1.5 drive could help in that dept, but it sounds like that's out for now.

Rene

Rob,see how easy it hits 6000 with the 30's,if it hits it real easy get a pair of 32's and work on them till it its perfect,if you have to trim it and hold it quite a while to hit 6000 with your 30's you'll be disappointed with steeper props. My boat pulls my 30 labbed real nice to just shy of 6000 when loaded hard,hits 6000 when loaded light which is the only time it can pull my 32 labbed and even then its a struggle to see 5800 with the 32. Your in the same territory,you just have to try it,Smitty