Dharr, maybe I'm misunderstanding, but you maybe confusing the pitch as taller or shorter. It has nothing to do with height. Instead, the pitch, be it 17", 19, 21 etc, is the theoretical distance a prop travels in one revolution. Here's an article that explains further... https://www.boatingmag.com/how-to/un...opeller-pitch/
No one can be wrong that often so it has to be deliberate.
Here is the Mercury Prop Selector page. https://www.mercurymarine.com/en/us/...=18#!/step-one
Just put in your information, type of boat, performance desires, type of engine and gear case ratio and so on. (Choose 2.07 Gear Ratio for the Standard gear case. 2.38 for the Command Thrust gear case) The Selector program will then give you a selection of several types of Mercury Propellers.
And like I said previously, If you go with a 4-Blade, Mercury recommends that you choose the 4-blade with the same pitch as your stock 3-Blade prop.
No one can be wrong that often so it has to be deliberate.
Oh and how far below pad is your prop?
No one can be wrong that often so it has to be deliberate.
Well back to square one dealer confirmed its 2.07 gears....guess maybe my rpm meter on the dash is way off...gonna have to pick up a merc monitor or something to double check that I guess. Before I drop big money on a spitfire. I have a vendor deal on solas props. Up to the titan ( not including the scorpion) are they worth a darn or should I just jump on the spitfire? I definitely will double check the rpms before I do anything though.
My prop to pad is 5.25....if your running a 21p spitfire at around 5800 rpms at 51mph and you go to the 19p to up wot rpms would you lose speed because your going down in pitch or gain speed because your upping your wot Rpms
Last edited by Dharr; 11-11-2019 at 08:48 PM.
5.25" might be a bit too low. That will definitely rob you of some speed. You may want to check around and see what would be the best setting for your model boat.Originally Posted by Dharr
With the 2.07 gear ratio, you've definitely got a Standard gear case, and for the Tach, there might be an adjustment/setting on the back you can change. For my new 115 Pro XS, I couldn't and had to get a new tach. (An easy upgrade) I also got the Mercury VesselView. Easy to install your self and it connects via Bluetooth to your phone. Neat little add-on that gives you all the info you need.
As for the speed on mine... I believe it would be about the same speed wise. I do need to get the rpm's up to 6300, (From 5820) which is the max for that engine and what Mercury recommended to me. They said it is where to engine likes to be and where it will perform the best! And the prop? Hopefully the 19" prop will put me where I need to be and I won't lose any speed with the change! If I do, I'll stick with the 21".
I'm also getting a 4" Jack Plate installed this week to get the engine back into cleaner water. That should help as well. Where it is now, on the transom, I'm having some prop blow out issues at WOT and that is hurting my performance. While a 4" isn't that much, it should help some, plus it'll still fit in my garage!
Last edited by OBT; 11-12-2019 at 06:14 AM.
No one can be wrong that often so it has to be deliberate.
DHarr, I will have to get out an measure my prop to pad dimension, haven't ever measured that, 5.25 does sound a bit deep though. You said you are mounted second hole from the top right? Going up a hole to the middle of the five may help. Really need to get an accurate tach measurement though, I highly recommend the vessel view mobile setup. You click it into the data port on the motor, zip tie it to just about anything that doesn't move under the cowl, and you have all the data you could want on your phone. I generally run tach, hours, and fuel consumption on my main screen when I run across the lake, but it can do so much more. Great tool to have and then you don't need one of the smartcraft gauges.
Each hole is 3/4 of an inch. So one one will get you to 4.75 inches.
its all part of the dialing in process. A pain and time consuming but worth it in the long run. That dialing in process is why I’m adding the 4” manual jack plate.
No one can be wrong that often so it has to be deliberate.
So right now in the second hole from the top. I'm able to use all the trim but the last bump on the trim as I'm coming up I can tell I'm losing speed and blowing out. If I raise the motor one hole I will lose a little trim right? Also will raise rpms even more causing even worse prop slip numbers? I really need less boat in the water will raising help bow lift too? My water pressure is up to 35 at wot and goes up the higher I trim. My plate is around 2" above pad.
Sorry I took so long to get back to you. Been a busy couple of days.
From everything I'm seeing, you say it is a 115 hp Pro XS 4 stroke w/Standard 2.07 Gear case, than I'd get a a 19" Spitfire X7 (stainless steel) 4 Blade prop and I wouldn't look back. https://www.mertenmarine.com/12.7-x-...ller-8M0055550 You'll get good hole shot, good bow lift, better turning (Grip) and good top speed and the rpm's should get up around 6300 which is that engines max and according to Mercury, is were that engine will perform the best.
You'll also probably need a new tach that will work with that engine. (Unless the dealer can make dip switch changes to the back of the current tach) I had to get a new tach on mine and my dealer new just what I needed. Your water pressure sounds fine but try to find out what the "To low/Minimum" is so if you raise your engine to high you'll know if you have a problem.
All hulls/Brands are different, all top speeds between the same sized boats will be different. Learning to use and "not" over use your trim will be a factor. Sometimes when you raise the trim and the engine/prop starts to blow out, you'll have to back off on the trim some, including going into and out of turns and lake conditions. You have to "drive" the boat and work with what you've got.
Maybe raising the motor one more hole and/or adding a 6" jack plate will add some top speed. But with your boat and that engine there are limits. You might get it up to around 48, 49 maybe 50 mph, but that's probably the max. Higher speeds could be down the road with your next boat and a bigger engine.
Last edited by OBT; 11-16-2019 at 10:55 AM.
No one can be wrong that often so it has to be deliberate.
Prop slip and handling are all I'm really looking for if I can hit 47 is be really happy but handling and a little more lift is my main goal ill look for a spitfire and see what happens.
I think you'll like the Spitfire X7. Stainless Steel props are always better performers than aluminum. I think you'll see the difference.
Cost wise, they are more expensive. Merten Marine (Same as Boat Propeller Warehouse) probably has the best price. Good Luck.
No one can be wrong that often so it has to be deliberate.
I was just looking at the Mercury motor page for the 115 Pro xs and they don't offer the CT on the 115 now just the 2.07 lower. The CT and the regular lower are available on the 115 regular four stroke.
Update..finally made it to the water everything just thawed out. My local prop shop maybe is using me as a guineapig? sold me a ballistic xhs 19p. Said it's supposed to have stern lift of a x7 and speed of a fast 3 blade. Average speed 46mph did hit 47 with the right conditions a few times...still high on rpms the limiter alarm went of once, but the water and temp is really cold right now so im going to get him to add cup to it today. Prop grips good. No blowout in corners. Porpoises a little in the mid rpms but I can power through it. So far im happy hoping the added cup brings my rpms down and speed up slightly.
Prop with cup added- dropped rpms a little water is still cold....before cup was added one person with a light load was 46mph. After cup was added.with two people and full tournament load holds a consistent 47 Seems to have more mid range acceleration. Took most of the porpoising out at mid speeds. I was also able to hold plane at 20mph before 24mph was about the slowest I could go before it dropped off plane.
What’s the part# for the ballistic xhs 19p
Always Ready!
Im not sure it's a michigan wheel prop ..only seems to be popular with speed boats
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