Yamaha F70 - Looking at props

Ralphy · 13 July 2013, 09:40

I have a Zodiac Medline 500 with a Yamaha F70 4 Stroke, it has the standard white Yamaha prop on it. At WOT around 6100 RPM I tend to get around 29 Knts give or take a few depending on the load on board.
Had the boat for over a year now and I am now wondering how much more speed It could do with a different prop, I have no idea how the different types of props affect the speed and performance so if anyone could help it would be greatly appreciated.
I have found the Performance Bulletin for my boat and it shows a top speed of 39 MPH, Is the prop used there the standard or a different one?
Thanks for any help
Ralphy

matt h · 13 July 2013, 13:20

we need to know what prop pitch is on there, almost def you could go up a pitch or two, i would expect to see 35 knots approx at 6100 rpm

ShinyShoe · 13 July 2013, 13:44

Only you know whats fitted to your engine. Propellers | Yamaha Outboards
The test was with a 13-1/4 x 17

Ralphy · 13 July 2013, 17:47

I'll go down to the boat tomorrow and find out which prop it is exactly

Ralphy · 14 July 2013, 17:03

I had a look today, It said 13 1/2 - 15 - K.