Posts: 3508
Location: Elk River, Minnesota | Hi Again,
Did a little number crunching on the numbers you gave me. Figuring the Ficht has a 1.86:1 gear ratio (for what I could find...please correct me if I am wrong) and a max RPM of 5500 (again, please correct me if I am wrong on this), your 22 pitch prop would get you 60 mph with 10% slip. Now...using your speed in this case, your slip is roughly 30%, which has me wondering a couple of things:
First, if the prop has been worked on, it may have had pitch changed, and if it has been shaved down in diameter, would lead to higher RPM values but lower speed. If the prop had a file taken to the blades at some point, it could be creating more slip duo to how things have been filed down. Do you have any pictures of the blades you can take and post?
Next thought is if the prop has seen better days, I'm wondering if you might have a bad hub, where the prop is slipping on the hub, thus giving you higher rpms, but not the speed.
From a very rudimentary standpoint, I think your pitch is about right, but if the prop is in great shape, I wouldn't hesitate to try a 24 pitch and see what happens. Sometimes the prop is just not matched to the rig very well and tons of slip come in to play.
Since it is an OMC product, if you can get a hold of an OMC raker in a 22 or 24 pitch, I'd say try them. If the 22 pitch gives you better numbers than yours, it very well could be your prop is not matched well, or has something else wrong with it. If you create same numbers on the 22, try the 24. That should lower your rpms by about 400 putting you right around the top end of your rpm range (again, if my numbers are correct abobve).
Where in the Metro are you? |
