I have a DF 175 which is the same motor on a 659 stabi running a 15x21 3 blade SS suzuki prop. Looking to change to a 14x20 4 blade to improve mid range and economy. I have heard of guys running 16x20 suzuki props with simular results but better economy mid range.

Thanks,

Based on the existing rig, my thoughts were to go 15 3/4 x 21 3 blade SS Solas L3, but the dealer who knows the boat recommended 23", which I reckon might be a bit too tall.

Thinking back, he probably didn't twig to me talking 15 3/4" diameters.

I want to focus on mid range, but still want WOT in the recommended 5000-6000 rpm range. (ideally 5700-5800).

Suppose with this in mind I should be thinking 4 blades, but have little experience with them and need to try and pick this right first time up.

The 16" diamater V6 props work well with these motors, I had a 16x20 on my old DF150 and now ive got the same prop hanging off the 175.

Cheers

Thanks Luke, Ended up choosing the 15 3/4 x 21. Did some prop calcs and a 23 would have been too tall - (and even if it could push it the top speed would have been ridiculously high) Going from a 14 x 19" my old Johnzuki DF115 with a 2.59 ratio to a DF150 with a 2.5 ratio is going to see some of improvement. And the extra torque of the big 2.9L donk should push the 21 just fine. I was closely considering a DF175, but thought the DF150 would do OK. (boat already does 35 knots with the 115 - albeit only 1-up with canopy down) The guys at Chivers recommended 150 for this hull too. I'd be really keen to see how you compare the 150 vs 175 ? What boat have you got it on ?

Well, new engine is finally fitted and I ran her in on the weekend - what an unbelievable difference the Big Cube torque & big diameter prop make.

The Solas Lexor Plus 15 3/4 x 21 seems just about perfect for effortless cruising @ 25-30knts / 3800-4300 rpm, but will need to check fuel rates over time to see what the economy is like and find the sweet spot.

Weather was pretty crap, but I was able to give it a couple of WOT squirts after 7+hrs of by-the-book breaking in.

Bow trimmed down into chop with 15knt cross-wind gave s GPS speed of 42.3knts @ 5950-6000rpm (1-up, canopy off) - vid link below. (cam was still hooked up after taking the kids for a ride).

http://www.youtube.com/watch?v=VTiljEp3mZk

(Excuse my choice of music - the camera mount was loose and making a sh!t rattling sound, so I added some music to drown it out)

A later squirt in less choppy conditions, engine trimmed out 60% gave GPS speed of 44.4knts @ 6050 rpm with more to go - so I could s'pose go up in pitch, but 44+ knts is plenty for me  - plus I reckon it'll be great as it is for offshore work, loaded with canopy up.