New Suzuki 115hp outboard top end speed and rpm issue

[Hoosmatroos]

When the motor is on the correct height then yes, you should ga for a lower pitched prop. Question is 1 or 2 steps.

[Stingrayzuke]

The prop on the boat now is 23 pitch. The next size down, at least for Suzuki is 21. I am going to see about testing that prop, hopefully the dealer and Suzuki will let me swap it out since it does not seem to be propped correctly. I am wondering if they will make me pay for a new prop since technically the max rpm are in range (5000 to 6000) but hopefully they are reasonable enough to put me in the optimum range.

[Kartergreg]

The prop on the boat now is 23 pitch. The next size down, at least for Suzuki is 21. I am going to see about testing that prop, hopefully the dealer and Suzuki will let me swap it out since it does not seem to be propped correctly. I am wondering if they will make me pay for a new prop since technically the max rpm are in range (5000 to 6000) but hopefully they are reasonable enough to put me in the optimum range.

Mine came with a true Suzuki 22 pitch prop. I dropped to a 20 pitch which got me just to 6000 when I am alone with a light load. The new prop was a stainless Powertech that cost me $270 from dansdiscountprops.com. Very happy with it, and they make 17 thru 22 pitch for our motor. My dealer was not helpful when it came to getting the right prop. Guess he figured they got close enough.

You should be right up there to 6000 alone with a light load so that you will have decent performance when you have a heavier load. I keep reading that our motors like to rev.

[tnadeau]

Thank you for posting the photos. That helps a lot. Your outboard was way too low to begin with. Very concerning the Dealer wasn’t helpful. Perhaps a call or email to the Dealer’s parent company will get some changes made. When dealing with propellor selection outboard height on the transom must be correct FIRST. When height is correct and the anti-ventilation plate immediately above the propellor is skimming the surface at cruise and optimum trim angle THEN you start dialing in max RPM by changing prop pitch. Perhaps make another run and verify outboard height is correct. If it is THEN a pitch change of 2 inches less pitch will bring you up to 6000 RPM. Don’t worry about blow out in turns. That is what trim is for. When you enter a turn trim the outboard down and as you exit the turn trim the outboard back out to where it runs best.

[tnadeau]

"When I told the dealer I needed a prop with two inches less pitch, he suggested I go to a prop shop in town and have them shave off the two inches....at my expense LOL.” Did the Dealer really say that? Shave off 2 inches? Hahaha if they did. Changing the pitch doesn’t shave anything off the prop - the blade angle is less to have less bite (lower pitch). My Suzuki dealer swapped my prop in an even exchange for the one they originally supplied. Be aware the exchange won’t happen if the prop is damaged in any way.

[Stingrayzuke]

So I have somewhat of an update, or at least a partial update, and a question.
Recall that I had the motor, 2017 Suzuki DF115A, raised two positions. This helped raise my top speed and RPMs but still was only reaching 5500 RPMs.
I asked the dealer for a 21 pitch prop (currently 23). When they said they had one for me, I went to pick it up and it was a Solas Rubex 3. This prop has a diameter of 13.2 inches. I believe my current prop is 14 inches. Anyway, the Solas website says to use the Solas Rubex 3 Plus for the Suzuki motor, diameter of 13.875”. The dealer said they had the smaller diameter in stock and to try it since I was trying to raise RPMs and the smaller diameter might work. So I tried it and here is what I found: The hole shot was about the same in terms of time to plane I think, but I had more bow rise than before. The stern seemed to sink down into the water at first throttle much more than before and did the same when coming to a stop. As far as WOT, I did not do a good job of getting full data. I did take it to full throttle without trimming up and got to 5700 RPM, but speed was only 41 mph. I forgot to trim up to max it out. I think I forgot because I was already convinced I did not like the prop. The motor sounded like it whirred more than it should. It just seemed like it was spinning too fast at a given speed.
So my question is, does this make sense, that a smaller diameter would cause less stern lift? That is not something I want to compromise on, especially since that test was with nobody else on the boat.
My inclination is to just insist on getting the 21 pitch Suzuki prop with the same diameter I have now with the 23 pitch. The other option is to try the Sols Rubex Plus, but I wonder if the blade design is also at play here.

[Harper]

Lots of variables come into play, and since the dealer basically forced you to change at least three of those variables at once (diameter, pitch, and manufacturer), it's impossible to make a judgment. Same diameter prop (14"), same manufacturer (Suzuki), and drop the pitch to 21". That's the only way to effectively make adjustments to find the right prop.

You should always trim down for your hole shot. Doing so keeps the bow down and gets you on plane faster, then you trim for performance.

[Moonlighter]

A smaller diameter prop wont provide as much sttern lift. And will be more inclined to cavitate. It is simply a function of the amount of blade area being smaller.

Gee, your dealer is making hard work of this!!

I agree - tell them you are not satisfied and want a Suzuki 14 x 21 prop, nothing else! You paid for the correct SUZUKI prop, not a cheap Solas.

[Stingrayzuke]

Yes, I told them that today, that I want only the Suzuki 14 x 21 prop to try next. Hopefully it will not take too long to get in and it will perform well.

[tnadeau]

See what a difference proper motor height has on performance? You could go down in pitch at least 2 inches as long as diameter stays the same.

[D'oh999]

My Dealer Started at a 19" (Merc Dealer also) then a 21" then a 23" before He got to 6100 and not on the Limiter. He had to order a SS for me. Let me run the Aluminum 23" until it arrived. All Suzuki props.

The SS made a night and day difference, not in top end, but hole shot and turns.

[Stingrayzuke]

D’oh999, what motor? What rpm did you start at? Sounds like you went up in pitch so you must have been too high in rpm originally? Also, what led to the dealer being willing to give you a SS?

[Moonlighter]

I doubt very much if the dealer “gave” him a SS prop for free. Either it was included in his original deal, or it cost extra. 😂.

I think that you would find that the Suzuki 14 x 20 Stainless Steel would be a very good match now that the engine height is better.

As I mentioned earlier, that is what I run on my boat, and it is a very popular and effective choice for many boats running the DF115/140’s.

The SS props flex much less than the aluminium ones so the 20” should be close to perfect. It will grip the water better, accelerate better and hang on better in corners. It might even allow you to lift the engine 1 more hole, and give you even further gains.

I agree with D’oh it will be night and day to the alloy 14 x 21.

But of course it will cost you some more to buy one.

[D'oh999]

D’oh999, what motor? What rpm did you start at? Sounds like you went up in pitch so you must have been too high in rpm originally? Also, what led to the dealer being willing to give you a SS?

Mine is a 140A so Max RPM is above a 115A at 6200. Yes the SS was negotiated in the Deal, right from the start it was "with a Shiny Prop"

As I said in the first response to your thread, my boat is lighter with less deadrise and a 140, and I am at a 23" pitch, so you started with way too much prop.

[Stingrayzuke]

The Suzuki 14x21 aluminum prop has not come in yet but if it works out I will need a spare anyway. I would like to consider a SS so perhaps the 14x20 would be the way to go. What would I expect with RPMs going from 14x21 aluminum to 14x 20 SS, would it be expected to be a wash? Also, where is the best place to buy Suzuki props, is there a website that offers better prices than I would expect from my dealer?