AL 3 blade 13x15 -> SS? 4 blade?

[sandiegosteve]

Desire: Better hole shot and more power in the mid-low planing speeds.
Questions: Would a SS prop help? Would a 4-blade prop help? SS 4-blade (AL is a potential option)?

Last year I bought a new Defiance Yellowtail 195 that came with a Yamaha F115 4 stroke. The motor sits back on a bracket, so the overall boat is more like 21-22' with the bracket in terms of running attitude. It also has a pilot house on it, so top end speed is not a major concern. Add some wind, and I go slower.

The boat came with a factory Yamaha 17" aluminum that gave WOT was ~5,400. The dealer gave me the 15" to try, and it is better at around 6,000 RPM.

Now I wonder should I just be happy, or would a SS and maybe a 4 blade prop help. As I add weight or get into a nasty sea state coming home, I spend more time in the barely planing speeds.

Doing some research, Yamaha doesn't make a 13 x 15 in SS, nor do they make any 4 blades that come in the 14-15 pitch range. There are some OEMs that make aluminum 4 blades in the 14-15 range and some SS 4-blade in the 14-15 range. There are also some SS 3-blade options. I'm in San Diego where if I hit a rock, I am also on the beach. I'm not worried about damage from hitting submerged rocks. Floating things, yes, but that isn't a reason to stay AL on its own.

Current set up:
1) Performance issue you are trying to correct.

Hole shot and better low end. Drive/power in a short sea state (Acceleration helps there).​

2) Current prop manufacturer, model, aluminum or stainless as a minimum.

Yamaha, 6E5-45947-00-EL, Aluminum​

3) Current prop diameter and pitch (required).

13.5" x 15"​

4) Wide open throttle RPM and speed with an average load (very helpful)

Just me on the boat, 5,900 to 6,100
Add another person it drops to 5,800 - 5,900.
Yamaha says 5,500 - 6,000 is target, but these motors like to be at the top of that band.​

5) Engine/drive make, model, year, and HP

Yamaha F115 4 stroke, 2008 (? - new from factory)​

6) Boat make model, year, length and weight

Defiance Yellowtail 195.
Factory weight with engine is 2000 lbs. 40 gallons fuel, and I've added a 42 gallon bait tank. I think it goes more in the 2,800 lb range loaded.​

Flat water WOT speed with just me is about 30 knots. I cruise in the 22 range if the seas are small and 14-18 when bigger. That is where I would like more performance and with some luck better economy.

Corollary question: WOT at normal load... for me that is full fuel, full bait tank, cooler and 2 guys. Most people seem to measure for 3/4 tank and 1 person. Should I be doing moderate load or full load?

 

[steelespike]

Re: AL 3 blade 13x15 -> SS? 4 blade?

Generally a 4blade will inprove hole shot.It will stay on plane better at reduced throttle.
Also may handle better at speed and at the dock.It will reduce max rpm so it is usually suggested you lkower pitch about 1".There are 15" and 13" 4 blades here at iboats.
A 15 would almost surely lower your rpm.The 13 could raise it 200 to 300 rpm.
Not carved in stone as changing brands and boat design can alter the effects.
You may be able to find a dealer that will let you try a number of props with the understanding you will buy one.A deposit is usually required.
The Solas Amita has had good predictable results.
As far as saving fuel you probably couldn't measure it without a flow meter.