Another request for prop info

[aaa1950]

I have read a great deal about selection of props and I find it is not a one size fits all situation. I have always believed that the old saying, ?keep it simple? is the best policy. Good luck with that from all the technical information and discussions I?ve read on the iboat forums. Having said all that it?s my situation. I own a 2012 Hurricane SDS with a 2012 Yamaha 115hp 4 stroke, stock 3 blade 13 1/4 x 17 prop. I can fish with my boat but it is primarily used for tubing, skiing, cruising around the lake. I have used it in the river and intercoastal waterway to fish but mainly stay in the lake. I realize that a modified hull like mine will not have the same characteristics as other types but I?m looking for feedback from the knowledgeable folks on this site, and respect each opinion offered. What I?m looking to do is improve my hole shot and getting to plane towing a tube or skier while also improving handling. Obviously towing a tube is more difficult and getting to plane takes a little longer. From what I?ve read changing to a four blade prop will accomplish what I want. Just like a lot of other people I would like to know if I should stay with a 3 blade and reduce pitch or switch to a 4 blade. And if I switch to a 4 blade do I stay with the same pitch. The Yamaha performance bulletin for my boat states at 4000 rpm I should be running 21.7 mph, and at 6000 37.4 mph. My WOT is right at 6000 rpm. Thus, the motor manufactures data and from my experience so far while trying to duplicate the testing conditions as best as I can, I see almost identical results. No additional gear added to the boat to improve handling or hole shot.

Sorry but I don?t have the tech info on the motor such as gear ratio, etc. right now. So I?m just throwing this out there for discussion. Thanks in advance for your feedback.

 

[SkiDad]

Re: Another request for prop info

i think id be looking at a 16p 4 blade.

 

[aaa1950]

Re: Another request for prop info

i think id be looking at a 16p 4 blade.

But according to what I've read would not decreasing the pitch increase the WOT? I'm already at 6000 rpm WOT now, would changing to a 4 blade compensate for that? Not arguing with you, I'm just not experienced enough yet to know.

 

[SkiDad]

Re: Another request for prop info

i haven't done a 4 blade yet - but I hear you loose 100-200 rpm going to 4 blade - so dropping 1 pitch should get you back to 6000 approximately. Of course a lot of this is trial and error b/c you will be switching prop brands. if you rpm was lower i would be recommending a 15p but you would have to watch your rpm. I think the yamaha props might me a semi cleaver type and that will get you high rpm by itself i think. A person that is very knowledgable is Ken at propgods - you might check with him b/c he is the master.

 

[MikDee]

Re: Another request for prop info

Just looking for a better hole shot? Put a Doel fin, or smart tabs on it. That should get you quickly thru the planning hump.

 

[Starcraft5834]

Re: Another request for prop info

17 4 blade......you might drop rpm a smidge.. your top end speed will go down a mile per hour or two.. you will appreciate your boat jumping on plan quicker and get there with less throttle too.. handling in general at slow speed will improve greatly... when I took 3 blade off my cuddy in favor of 4 blade, was like night ant day.. if you dont mind going a few mph slower at top end.. you will like the 4 blade... more overall benefits in my view... others will chime in at to recommended pitch,, would think a 17 would be in ballpark now..

 

[aaa1950]

Re: Another request for prop info

The diameter of the 17p 4 blade props I'm seeing online are 13" instead of 13 1/4" that I have now. I don't see that making a huge difference. If anyone sees a potential issue from changing the diameter of the prop other than clearance let me know. Please keep in the ideas flowing. All your ideas will help me make a informed decision.

 

[MikDee]

Re: Another request for prop info

Diameter usually automatically goes in proportion to certain classes of props. No need to worry much about it, unless you have a heavy inboard, or I/O, then you can get bigger diam. props. to prevent prop "blowout" in the turns, & at low speeds, especially in heavy seas., like I had on my old 24' SeaRay cuddy. A 1/4" difference would probably not even be noticed.

 

[aaa1950]

Re: Another request for prop info

Thanks, that eases my mind a great deal.

 

[jestor68]

Re: Another request for prop info

With your 2.15 gear ratio, you're showing about 18% slip now, which is a tad high, mostly due to the aluminum prop you're using.

Given your motor's rpm range of 5300-6300(115 hp @ 5800 rpm) a 15 pitch 4 blade should give you the acceleration improvement you're after, while gaining about 100-200 rpm at WOT.

In aluminum the Solas 4 blade would work well, but to realize the full potential I'd go for the Solas 4 blade SS Rubex or HR Titan.