which prop - or neither?

[wmbreck]

http://johnsonlarson.homestead.com/index.html

I've been messing with our new/old Larson boat all summer. I've written several posts and received great info. It is obvioulsy underpowered but some of what I have done has increased the spead - new prop, trim, hydro foil, and especially messing with the spark advance to get more rpms. Still not sure if that is right for the moment. But at least the boat gets on plan after a few minutes and will do 17-18 with 2 aboard and 22mph with one.

But I was wondering which of the 2 props seen here would be better. If you scroll down to the bottom you'll see the two. The black one came on the boat. I was told that the owner put it on for fishing.trolling? The blades on it were more narrow and the overall diameter just a bit smaller. The white one that I took off my 25 Johnson was a little larger and the blades fatter/rounder. Hard to tell the difference in the pitches. But I was wondering which would be best 'overall' ? I'd like more top end of course, but not if the black one won't get me out of the water. Maybe both are insufficient? Any ideas?
Thanks!

 

[usskydvr]

Re: which prop - or neither?

The black one clearly looks to have more pitch than the white one, which should give you more speed, assuming your engine can turn it at the proper RPM. You really need to get p/n's or other way to find out what the dia and pitch of each of these are and compare them to what you currently have.

 

[steelespike]

Re: which prop - or neither?

Without the rpm there is no way to be sure where your at.
A tinytach is about $47 and easy to install.By your description you need less pitch,
assuming the motor is healthy.Are there no numbers on the barrel near the base of the blades.A prop shop can measure them for you.I think the 28 on a more normal size(weight) boat should do over 30 I think 25 to 28 with one and over 20 with 2. If it won't plane without the fin something is wrong.The fin should help you plane but if it doesn't clear the water on plane it will hold the speed down.