Another Prop Question

[pair of jacks]

Currently running a 14 1/2 inch x 15 pitch prop on 175 Etec- get about 5400 rmp's top end. The prop is a no-name aftermarket stainless steel and the blades have little to no sweep to them. Thinking about going to a Evinrude Rebel prop 15 3/4 inch by 15 pitch with pronounced swept blades. Have heard varied guesses on what performance will be gained or lost. Before I spring for $400 would like to hear some opinions- thanks!

[ct9amr]

Post up on propgods.
Ken will probably have a good answer for you.

http://www.propgods.com/

He was right on the money for my Contender.

[Bushwacker]

Originally Posted by pair of jacks

Currently running a 14 1/2 inch x 15 pitch prop on 175 Etec- get about 5400 rmp's top end. The prop is a no-name aftermarket stainless steel and the blades have little to no sweep to them. Thinking about going to a Evinrude Rebel prop 15 3/4 inch by 15 pitch with pronounced swept blades. Have heard varied guesses on what performance will be gained or lost. Before I spring for $400 would like to hear some opinions- thanks!

The OPTIMUM rpm range on the small-block V-6 E-TEC is 5300-5500 for the 2007 models like mine, but it's 5500-5600 for all later models per this web site: http://www.etecownersgroup.com/post/...u-2011-5396435 Your WOT rpm may be a couple hundred rpm too low depending on what year your motor is. Before you change props, make sure motor is mounted high enough that you can clearly see the AV plate out of the water when you're up on plane. And of course make sure the tach is accurate (not a problem if using I-Command!)

I've heard good things about cruise and min planing speed performance of the Rebel prop and asked my dealer about it. He said his experience was that it was better suited to the big block 3.3/3.4L motors, especially on a heavy boat. He didn't think the 2.6L motors had the torque to spin it fast enough unless they were on a boat much lighter than mine, and I think your boat is a fair bit heavier. I'm running a 4B 15 x15 PowerTech prop that uses the old SST blade profile and spins 5450 pretty much regardless of load at about 39-40 mph. I'm giving up several mph in top end, but it has an awesome hole shot, stays on plane down to 12 mph, and has averaged over 4 mpg on trips of 250-700 miles. I'd like to try a Rebel sometime, but I'm not sure I can improve on that performance very much! If you're able try one, let me know how it works out! Denny

[DonV]

Denny.....please take it easy! You keep bringing up the 4 mpg, which you darn sure should be quite proud of, so just to let you know us 2 mpg guys are really jealous!! Seeya Friday!!

[Commander Coo1]

I am not a Sea Craft owner, just an admirer and reader. My 20' Whaler Outrage does well with a 15p Enertia on a 175 E-TEC. I found the Rebel 15p held my rpm down too much. What kind of speed do you get at cruise and WOT? Ken from propgods.com really helped me out!

[pair of jacks]

Yes, I have been talking to Ken- very helpful for sure. Wide open is 30/31 kts. and cruise is 24

[Commander Coo1]

looks like you have about 15% slip at WOT which seems pretty high. The Enertia got me about 2% slip and the Rebel was "0%". you may end up needing to come down in pitch unless you pick up a decent amount of speed. My setup weighs about 4000lbs loaded and tops out at about 43mph/37kts.

[Fr. Frank]

Originally Posted by Commander Coo1

looks like you have about 15% slip at WOT which seems pretty high. The Enertia got me about 2% slip and the Rebel was "0%". you may end up needing to come down in pitch unless you pick up a decent amount of speed. My setup weighs about 4000lbs loaded and tops out at about 43mph/37kts.

No prop swings without slip, period.

An extremely well matched prop-motor-hull setup will have around 10% slip. Average minimum slip used to be 15-18% for most dealer setups. Occasionally, you may see a setup down around 8%, but that's pretty rare. If I recall right, ESD gets about 51-52 mph at best trim WOT with that 19" Stilletto on his XRi 200, which with the most common gear ratio on that motor being 1.81:1, puts him near that magical 8% ratio. (Correct me if I'm wrong on that speed) OTH, if he has the available/optional 1.65:1 gear ratio, then his slip is a more normal 14%.

Here are three examples:
The most efficient setup I have ever seen on a regular (non-race) hull was on a '69 16' Whaler with an '85 90 hp Yamaha turning a Yamaha 21P SWS semi-cleaver SS prop which got an astounding 6.7% slip at 5800 rpms/46 mph.

I once rigged an 21' Allison XTB mod-V race hull with a Yamaha Excel 220 with a blueprinted hull, nose cone, hydraulic jackplate, and a custom one-of-a-kind Second Effort Marine 31"P through-hub prop which got all the way down to 4.5% slip at 6470 rpms/108 mph.

Back in the early days of PowerTech, I had them design and build me a custom prop for my '72 Seafari running a blueprinted Mercury XR4 150 (190 hp) with a 1.65 gear ratio. It was a 15"Dx16.5"P 3-blade, and at 6050 rpms and 53 mph, I was achieving only 7.5% slip.

If you see a slip ratio being reported of 8% or under , I would suspect the accuracy of the propeller specs, such as prop labeled as 17"P actually being 16"P or so. It is not uncommon for aftermarket props to be as much as a full 1" different from their labeled pitch.

The amount of slip will also vary on the same hull-motor-prop setup depending on the efficiency of the trim and rpm setting being used. While I achieved as low as 7.5% slip at 6050 rpms on my Seafari, when I was cruising at 3800 rpms, my slip ratio was up to 14%, achieving 30 mph.

[eggsuckindog]

I can't imagine a 175 Etec on what looks like a 20 not being able to swing a 15 anything? Frankly I'm not sure it can be a 15, a 150 OMC on a 20 swings a 17 and I run a 19 with only 25HP, just seems odd unless its a 23.

[DonV]

Jeeeez Dog...a 15 pitch, of any brand, on a 20'er with 150 plus HP ought to spin the engine to it's max...and then some!!!!