prop slipping at high rpm
Having baseline data always helps with propping. The Bravo was slower at about 63 and also about 6300 RPM. Is it important to know your prop’s slip? 6 sec count, Bravo I FS 20 – time to plane approx. Then will see.. My goal is to have best fuel economy at cruising speed (23-28 mph), and top speed 39+ mph . Enertia ECO 17P or The GPS speed was measured using my Hummingbird unit and a phone app for GPS speed, and they both matched. For most bass, bay boats, and runabouts the spread between cruising slip percentage and top end slip percentage should not be big. You’ll likely want to take it to a marine mechanic or prop shop if you’re not handy. Once a hub is spun, there generally remains enough friction to operate at low RPM – sort of a “get home” mode. Sometimes, the hub only spins when the engine revs above a certain RPM, causing many boaters to wonder if they have spun a hub, are experiencing ventilation or cavitation, or have some kind of gear or power issue with their outboard. I have something very interesting going on that from past experience is not adding up. That ECO is hooked up so well I wouldn’t change a thing. thank you for answer, Engine RPM Chart for Proper Boat Propeller Sizing. Later when I will see actual data it will be easier to upgrade – if needed. TM on bow. The length of the arrows reflect speed in MPH for both the measured speed and the theoretical (no slip) forward speed. Hi, Save my name, email, and website in this browser for the next time I comment. BTW I was checking REV 4 XP 16 RH + flow torq ss adaptor for 5/4″, but did not find anybody offering it. If you have the proper tools, you can do this process yourself. I’ve been experimenting with my setup under different conditions and have some concerns. If you take the rpm’s, gear ratio (1.75), and the max speed according to the prop slip calculator I am only at 2%. Back in the day when the Everything You Need to Know About Propellers book was published, the Internet didn’t exist and you had to actually use these cumbersome formulas or rely on the Quicksilver Propeller Slip Calculator. You are at 14% slip which is awesome for a Bravo I XS setup. Is there any benefit to adding RPM by tweaking things such as going to lower pitch prop or raising engine further? For the moment i have enertia 22” and Looking for a economical cruising speed. 5940 max rpm @ 53 mph – couldn’t over trim as Verado limit hits 8.1 and stops Still in break-in with 4hrs. Is it true that Cleavers have negatively progressive pitch? thanx a lot.It is much more clear now. It is a tell tale sign that an engine is too high when the slip number starts to increase (higher RPM without increasing speed). Our propeller engineers study props at the 7/10 radius (70% of the distance from the center of the prop hub to the blade tip). It should free up the motor for much better hole shot and acceleration as well. Today, you can get all of your prop information with our Prop Slip Calculator App. As we know, it turns like a 2 inch stiffer prop – and thus the slip #s range from 8 to 16% depending if you use the 19 or 21 in the slip calc tool. Response to my Prop School series has been gratifying. Tempest 21 – full of fuel, driver only, musky gear, empty livewells Nice cruising boat with a 17P Vengeance prop. Propeller – Don’t Fix What Isn’t Broken, California Transparency in Supply Chains Act. Blades operating with an angle of attack create a negative (lower or pulling) pressure on one side and a positive (higher or pushing) pressure on the opposite side. Your email address will not be published. The Nitros have been performing very well with the Bravo, both top end and handling. The 19.5 pitch ECO XP from Racing could give you 1-2 mph increase. I care most about fuel economy do I stay with a tempest and go to 17p or would a enertia eco be better. It is the most misunderstood of all propeller terms. We ran a 27 Bravo XS on the 2015 Ranger while others Tried to run the 25-26 Fury. To answer your other question, we take the Revolution 4 and fine tune it at Mercury Racing, in doing so we are able to offer different pitches than standard so that we can dial in motors to their peak RPM range. Engine is Mercury 115 CT PRO xs 2017, ratio 2,38. It sounds like you have your rig dialed in perfectly, low slip on a tritoon is a great thing, I wouldn’t change a thing! Hole shot is outstanding. Scott called in and he ended up going with the 20 pitch Rev 4 XPs. With a positive angle of attack, even higher pressure below the wing creates still more lift. Currently running an Optimax 200 on a Recon 985 with a 22P Bravo 1 XS. Every hull has a different balance and water flow, we adjust our propeller designs accordinly. The most RPM’s I am able to turn is 5350 according to the gauge. I guess I don’t understand the issue some have with losing RPM if you’re gaining 10 to 15% top end. Slight chop on the water You will likely feel the prop slipping at high RPM. Similarly, marine propeller blades operating at a zero angle of attack produce nearly equal positive and negative pressures, resulting in zero thrust. My max speed (GPS) is 68mph. My gear ratio is 2.15 and at around 5000 rpm I have 33,8 Kts speed, measured with my lowrance gps. I am having trouble identifying the best prop for overall use with this boat and motor. The fourth blade and 15.25 inch diameter will help you make the most of your hydraulic jack plate. If an airplane wing were symmetrical (air moves across the top and bottom of the wing equally), the pressure from above and below the wing would be equal, resulting in zero lift. Your thoughts greatly appreciated. Realistically, you are running a prop that is closer to 25 or 25.5 pitch, plug that number in and you are closer to 7%. The GPS speed was measured using my Hummingbird unit and a phone app for GPS speed, and they both matched. I hope you have found my Prop School blog series both educational and useful. Four and five blade props have taken the place of many three blade props because they offer more grip at higher engine heights, better boat control, and more lift. Thank you for all. The number of blades on a prop has become very important over the last few years because everything has gotten bigger- engines, boats, and gear cases. But, when RPM is increased, the engine revs with little or no boat acceleration because the prop begins to spin. The longer, flared barrel will help with hole shot and carrying heavier loads. Crunching the numbers I was pretty confident that there would be a Bravo fit. 4.5L 200 to haul the kids around with. With the mark in place over the inner and outer hub, it’s a simple matter to pull the prop and see if the mark has broken in two. I’m hearing keep the pitch same and try the high five. I have a 2005 Checkmate Pulsare 2100 w a 2005 promax 300x with a sportmaster 1.62 lower.currently running 27p Trophy Plus that will turn 5900 at 80mph…it seems like this combo should run faster to me.. what prop would you recommend?? Scott says hi as well. Slip is the most misunderstood of all propeller terms, probably because it sounds like something undesirable. A 26 pitch Pro Max may come close but it won’t be any faster. The Fury could still be faster on top end with a light load but the Bravo will carry loads, as you have found out. Nick, If you are mostly concerned with top end, the Fury is hard to beat. Slight chop on the water Copyright © 2020 Boating Magazine. Likewise with a prop, the lower the pitch, the easier it is to turn high rpms. The curvature of a wing reduces static pressure above the wing — the Bernoulli effect — so that the pressure below the wing is greater. Any suggestion for dealer ? I wouldn’t change a thing. We tried a 24p and it was much the same. I have a 27 Tempest, but the boat has a nasty chine walk with this prop…. Is this ok, or do the prop blades need to be more submerged? Top end gains will be small, maybe 1 mph over your 25 Fury. Here’s our prop slip calculator: You helped me prop my 2015 Ranger with the Bravo XS and I have loved it from the beginning and have turned several other guys on to the Bravo and have cured set up nightmares. Should I jump up to a Bravo 29? A spun hub feels like a loss of power with excessive RPM. Prop Slip Calculator. Will post results when boat arrive. I guess I don’t understand how you can come up with a theoretical boat speed that does not depend on the pitch of the prop? Only if you care about insignificant, little items like thrust. My thinking is raising the engine one hole (+ 3/4″) would put it too high at 3″, and dropping to 21P would add 200 RPM but maybe not more top speed due to lower pitch. My question is am I too efficient? boat is a12 250 pro xs 12 Nitro Z8 10 inch hydralic jp i like the 16 inch diameter would this prop work looking for more speed and what pitch would be recommened thank. You can try raising the engine up one hole, I’m weary that the prop will start to slip. Rather, slip is the difference between actual and theoretical travel resulting from a necessary propeller blade angle of attack.


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