Stainless Steel prop pitch & blade question

Late this summer I bought a 2014 Merc 115 HP 4 stroke outboard for my 2001 Crestliner fish hawk. I kept my prop off of my 90 HP 2 stroke. It is a 13 1/4″ x 17 pitch that will push the boat about 38 MPH at 6200 RPM, which is at or near the max recommended RPM. I have been searching on line for prop recommendations and it looks like I will need a 19 pitch sst. prop. I see there are 3 blade and 4 blade props. Several different brands too. Does anybody on here have a similar setup with a sst prop? I am trying to avoid buying X pitch and finding out it isn’t correct and having to but Y pitch to see if that works. Your thoughts on 3 blade vs 4 blade and brand of prop. would be great too.

Need to know the boat length
and if current prop is aluminum or sst

3blade Vs. 4 blade – Generally you give up 2 to 4 mph (sometimes more). Biggest advantage with 4 blade is boat control in rougher water / larger waves. As an example – on Lake MI with 4 to 6 foot waves it is easier to stick a wave like a surf board and have a better bite with a 4 blade to control “riding” a wave. Also pulling a tube or skiers, the 4 blade bites more water. 3 blade with give you best top end speed.

Every boat is a little different with set up and weight distribution. Working with a local dealer, most will let you test run a prop (given no damage to it) to see what is best. There are a lot of great informative posts on here regarding prop design and what each part of the prop does. I would stay away from props that have the “mickey mouse ear” design and look for a better cutting rake and good defined cupping.

Remember its less that the last 1/4″ that actually throws the water. The other 99% of the blade cuts water.

The other thing someone giving you good advice, besides length, would need to know is the gear ratio for your outboard. There are two different gear ratios for that particular outboard.

Here is Mercury’s test info for a 115 4 stroke on a 1750 Fish Hawk.

I know several marine stores that will let you “rent” a few test props just give them credit card info and they hold it in case you damage the prop and they will let you go out and test them on your boat I’ve used hallberg marine in Wyoming MN and formula props in osseo MN I’m sure one closer to you will let you do the same thing in the spring.

Sorry I left out a couple of details. It is the 1750 length and current prop is aluminum. I live in Hastings so if you know any dealers around there that have a test plan that would be great. Should I stick with a Merc brand or have you guys used other brands. I was looking at Solas brand, anybody using that? Lower unit gear ratio is 2.07. It is not the newer larger 2.38 command thrust lower unit.

I bet you’d be surprised by the performance you would get out of a 17 pitch Mercury Spitfire. It is a 4 blade aluminum, but that prop was the best all around prop I could find for my Lowe 175 walk through with a 125 opti.

I tried 5 different stainless props, and never got much more performance out of any of them, some were worse. The hole shot with the spitfire has been great, I run low 40’s loaded down with a couple heavy guys, kicker, gear etc… They now make it in stainless as well with a little more cupping.

One challenge in that 115 and 125hp range is that it seems like a lot of those rigs really do well with an 18 pitch, which nobody seems to make in a decent aluminum prop.

Check out http://brainerdprops.com/ and give Ricky there a call. They call him propman and he knows his stuff. He sells a lot of powertech stainless props, I tried one and it was good, but I went with the 19, and need an 18. Just need to decide if I want to order it or not. I just didn’t think the performance gain was enough for me to justify over my spitfire. The powertech was the best perfoming prop that I tried though.

He has a “Demo Prop” program, where you put $30 down and he’ll send you the prop. If you buy the prop, he’ll put that towards the cost. One of the issues I had was bow lift, I always felt that my bow was dragging. That powertech did a really good job of bringing that bow up a little, which caused less drag.

I think it is important to know what you are trying to achieve with the prop change, top end or hole shot improvement? 4 blade is better for hole shot and reducing cavitation in turns or rough conditions as mentioned above. You mentioned a 19″ pitch, which would imply that you are trying to get more top end. A SS 19″, 3 blade prop would get you a couple more mph. Adjusting your engine height to optimum would also get you a couple mph. Most dealers mount the engine too low, which creates extra drag. Optimum height for performance is when on plane, cavitation plate is right at the surface.

Propmann responded to this string.

http://www.in-depthoutdoors.com/community/forums/topic/1675-impact-prop-selection/

As the string suggests, I would talk to him for a recommendation, etc.
The string includes results from my tests

The prop is incredible as everything improved on my rig.
I did not lose anything anywhere which I found unfathomable.

Right now the boat runs 38 MPH WOT at 6000 RPM. I could easily over rev it because I still have throttle left. I would like to run it at about 5800 RPM and should be able to go somewhere in the mid 40’s for speed. Hole shot isn’t real important but I don’t want to plow a bunch of water before it starts to plane out. So general performance. Friend has the same boat with a 115 4 stroke Suzuki and he is at close to 48 MPH WOT. So I am comparing MPH to his. His prop. pitch is 23 so the Suzuki lower unit gear ratio must be quite a bit different than the Merc.

That sounds pretty fast for a 115, not saying it’s not true, but that sounds to me like a rig that’s set up perfectly and running a higher pitch specifically for speed. 42 to 43 would be my estimate on your setup when dialed in, maybe a little more if you find the exact right setup.

I would still give Ricky a call, he might know of the proper 19 or 20 pitch prop for your setup. The highest top end speeds also come with the cost of lesser hole shot. I know guys who sacrafice hole shot for that top end, finding the best combination of the two is a compromise. Your 115 4 stroke shouldn’t redline until about 6200 rpms, so you can give it more than 5800 rpms with your current setup.

That was the nice thing about the powertech prop I used from there, it was a 3 blade with good hole shot, good bow lift and great acceleration. I tried it in a 17, but over-reved and still had the same top end as my current prop. I’m sure I could’ve picked up a few more mph going to the 18 or even the 19.

Thanks for your replies. I will be calling Ricky in Brainerd.