Little Prop Help Please

csvencer · #1 04-13-2012, 03:21 PM

I have a 14' McKee (it's not as nice as some others on here may have....but if floats) that I just put a 50 HP Johnson on. Right now it has an aluminum 11.75x17 prop and wide open she is hitting 6000RPMs. The boat is light right now (just dropped it in for a test ride) and the prop has a couple of dings. I was thinking I would need a 11.75x19 or even 21 to get me down to 5500 but I can only find 12x17 props. Think that will drop it down enough? I am sure the dings and the fact that it's aluminum and flexes, my 6000 may be bumped up a 100-200 artificially, but I just don't think adding a .25" to the diameter is going to get me down the other 3-400 RPMs.

Thoughts?

-Svence

tsubaki · #2 04-13-2012, 07:31 PM

List what you know about the engine.
The foot is the main animal, weather it's a small or large foot, thru hub, how many splines, year, model or even the existing part number of the prop you have or the one available that you know fits.
I think there were 3 foots for the 50 horse but 2 were normal in a given year range. Basically the big foot and small foot.

tsubaki · #3 04-13-2012, 07:37 PM

We had a similar problem on a boat I've got being over horsed. Tried twice having props repitched (cause we reached the normal available prop max) and finally just ran about 3/4 throttle to keep the rpm's within the engines suggested range.

spareparts · #4 04-13-2012, 09:57 PM

check your tach to begin with, then compare your prop to a new one, its probably worn out more than you realize, see if you can find a prop shop that will let you play around with different props. Their used to be Murphey's in Norfolk, I don't know if they are still around, but at one time, they were considered the best on the East coast. If you had posted this a few days earlier, I could have come by and took a test ride

csvencer · #5 04-14-2012, 05:38 AM

Thanks guys. The motor is a 1995 50HP non-commercial with the standard L/U (Don't know the ratio off the top of my head, can check the book when I get home). Current prop is a 3 blade, 11.75x17 aluminum. I am thinking that I don't really have too many options anyway as I can only find 12x17 and 11.75x17 props, everything else is too large a diameter. Spare, I'll see what I can find locally. I hope I can find a good shop because I may just pick up a 12x17 and see where that gets me and if needed add some pitch. The tach is brand new so I would think it's pretty accurate and based on the feel of the boat I would agree I need to add some bite. The prop slips when I mash the throttle and takes a second to bite, so I clearly have an issue.

I would have hooked you up for a ride if she was ready. Just finished rebuilding the carbs yesterday and splashed her ASAP to see how it ran. If you're in town again shoot me a pm!

-Svence