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View Full Version : Props, torque, Chine walk, Does this make sense???



mphatc
07-07-2005, 06:56 PM
I emailed a few prop service shops around the country. One wrote this back to me. and I'm not sure I understand it,as a matter of fact I don't! :confused:

Here's what they wrote:

"that motor has so much torque that you are cruising at peak torque so it is throwing you over on its side. I would try to play with weight in the boat to control the chining and get the CG’s right and then prop for a higher RPM because this effects the cruise speed, hole shot and acceleration when in the wrong prop. Additionally when you run a boat/motor at the inappropriate RPM for instance peak torque you will definitely get “Ill” behaviors out of the boat. Such as what you have described and until you can get to a higher Rpm the behaviors may ensue."

What we're discussing in the above is my 302 Ford / Bravo 1 in a Corsican. 318-319 ft lbs of torque and ~ 310 HP at 5100 RPM. It makes 333 HP at 5800, but I don't want to run that high. Also this boat has no helm, steers w/o any effort, and only leans over 1-2" at a cruise. In big waves, rough water, It feels like it wants to land on the starboard side, and to get it to land
comfortably I find my self correcting to port a bit. All this with the Mirage + 14 x 23P LH .
I can't undrstand how engine torque can cause the boat to chine walk . . How does the hull and prop know?? Am I really missing something here???? :confused: :bonk:

Help, all I trying to do is learn a bit more about props before buyig the correct one.

Thanks,
Mario

gcarter
07-07-2005, 08:30 PM
Mario, I'm certainly no prop expert, buy I did try a 14 1/4 X 25 Mirage+ one day in March. Compared to a Turbo, it was absolutely squirelly! It was the only time the Minx has chine walked.
It was explained to me the prop generates a lot of bow lift and puts the boat in a real loose condition. Some people like them, and the way they perform. I, for one, don't. It's probably a senior thing. :D

:wavey:

Cuda
07-07-2005, 09:23 PM
George, how many rpm were you getting with the 25?

gcarter
07-07-2005, 10:00 PM
A little over 4000. However, I'm beginning to think my tach is reading low. I just bought a photo tach on ebay to check it.