Okay--I had some time today to take my pontoon out and do some speed tests. Don't get too excited... we're talking 16-17mph here :-)
My pontoon is a 2002 24-foot Bentley 824 with a 50-hp Mercury motor. It's perfect for what my wife and I wanted, and the kids (5 & 4) think they're zipping across the water at 100 mph on their towables (hopefully we've got another 2-3 years before they say, "Dad, this is BORING!"). However, I'm a tinkerer, and I want to do a few little things to see if I can get 20-21 mph out of this baby.
Here's the problem. During testing with my GPS..., and I could consistently get 16-17 mph at 4500 rpm. Into the wind, against the wind, smooth water, calm water--whatever (I did hit 18 mph a couple of times. They need to put some hills on these lakes!). The speed increases every 1000 rpm were pretty proportional, so I assume I have no "prop slip" for the most part. Is this correct? However, here's the doozy....
From 4500 rpm to WOT (5500 rpm), there's zero increase in speed. Zilch, zero, nada. It always seemed to me that from 4500-5500 made little to no difference, and I confirmed that today with the GPS (other than a louder engine!). Sooooo... what could be the problem?
I'm sorry for the lack of info, but I'll check my prop tomorrow in the sunlight and get the size and pitch--I assume they're stamped somewhere on the prop? I also try to get the engine details, but I assume a 50-hp Mercury is pretty standard? Also, I'll try to take some pics to post on here, as well. The prop is aluminum, and the paint is wearing off. I just bought the boat and the prop was supposedly new as of the beginning of this year. It doesn't look damaged from a distant inspection, but I'll look closer tomorrow.
Questions:
1) Is this normal to see a zero speed increase at higher RPM's? If I'm hitting 16-17 mph at 4500, should I be getting 20-21 mph at 5500?
2) I know it's a 'toon, but will props (sized to top out at the rec'd 5500 rpm) that are higher-performance like cupped props (Hustler, etc.), etc., make a difference? I saw in a post somewhere on here that cupped props give you another inch of pitch... true? Not true?
3) I assume SS props on 'toons are a waste of money. Am I correct that SS props are best for higher HP applications and quick launches since they flex very little when power is applied? Or do they also help at top speed?
4) Does it seem feasible to hit 20-21 mph in a boat like this? I have *no* idea what the weight of the boat is. Other than picking it up and standing on the bathroom scales <grin>, how can I find out? Are boats required to have the weight stamped on them? I can say that the trailer that came with this boat is single axle, non-braking, and it rides it very well. I ask this because I noticed another similar post where the guy had a pretty heavy pontoon which made a big difference.
5) Do things like larger hydrofoils on the engine really help to avoid cavitation, prop blow out (what is that?) and such? Could this be my problem? Here's the link to one I saw for my engine: http://www.westmarine.com/1/1/8438-s...e-technol.html
Anyway, I'm going to do a few different things and see what it does to my top-end. I just don't want to go stabbing in the dark... I need some good, expert educated guesses!
Ahh, the fun of pontoons. 17mph is pretty dang good for a 50hp engine on a 24' pontoon. The issue of not picking up speed beyond 4500rpm on you engine is a combination of issues. First the pontoon is attempting to sort of plain out thus lifting up the prop into more turbulent water. Second, as the speed increases so does the turbulence of water under the pontoon due the wake from each pontoon hitting each other AND the underside of the pontoon creating even more "bad" water for your engine to try and get a bite. You don't state which 50hp Merc you have. If its a bigfoot then you already have quite a bit of prop area for the given hp. You could try "underskinning" or lowering the motor if its not down all the way But if you due get a good bite I think your RPMS will come down at WOT and you won't gain any more speed.
I'm about to go out and scour the engine to see exactly what kind it is. Are the bigfoots not all 4-stroke? Mine is a 2-stroke if that helps. I'll post again in a few with more info.
Okay--here we go. The prop doesn't have much written on it, but it says "SOLAS" on one side (manufacturer?) and 11.6x11 on the other. As for the engine and what-not, here are some pics...
Hopefully this will give all of the necessary info. Where can I find the info on my motor such as gear ratio (is it 1.83?) and such? I assume it isn't a bigfoot? Thanks!
Wow--those pics came out huge. Sorry for that--I should have resized them.
Anyway, Let me know if that gives all of the useful information needed (and feel free to decipher it for me!!!). I Googled the model number, and all it brings up are parts lists. Nothing on rec'd RPM, gear ratio, etc.
Would it be worth changing the prop to see what happens??? I'm bound and determined to see if I can crank 20 mph out of this baby. Gonna scrub the pontoons later today--lots of rough, "cakey" stuff on there.
Will nitrous oxide work on a two-cycle motor??? <grin>
i have almost the same motor on my suntracker,mine sez tracker mercury pro,my toon is 18',i get about 20mph @ 5200rpms,i cked it friday nite with 4 men & coolers fishing gear ect & was running 17mph @ 4800 or so,i dont know if you can get that much out of a 50 with 24' of boat but good luck,mike243
Yup--20 mph might be unreachable, but it'll be fun to try :-)
As for the engine I have, can anyone tell me if it's a bigfoot, etc.? Gear ratio for this motor and so-on? Just trying to get some details for all of the online calcs you see (slip, etc.).
Also, what about the prop? what exactly is 11.6 x 11? Would a higher quality and/or cupped prop be better? Or is Solas a top-end cupped prop? I noticed that in 11" props (I assume this is what I have) they have 10 7/8 and 11 3/5 props for my motor (if, in fact, mine is not a bigfoot). Would the slightly larger diameter give me better bite? Thanks!
I don't believe a big foot would have a 11" diameter prop.It uses a gearcase from a larger motor.I resist lowering motors(more drag) but you might try lowering the motor a hole it might help the push above 4,500.I think A turning point prop will help the top end a little
its obvious your having a lot of slip or perhaps some venting. above 4,500.The turning point Hustler in the same pitch will resist venting.You could also try a 4 blade pontoon prop drop an inch in pitch.You also could try very careful weight placement and elimination. and motor trim.Once you have the Hustler or 4 blade you might try raising the motor one hole.
Will you see 20?? not likely a 2 mph increase with a planing boat would be doing pretty good.When making changes do one at a time.
Okay--I have the pontoons cleaned, and man--they look brand new. It might not go 20 mph, but it *looks* like it'd go 40! LOL! I'll post a pic here tomorrow. As bad as they were (all kinds of rough, scaly, crusty stuff), it's hard not to think that it will glide a *little* better through the water. At 20 mph, friction might not be a huge detriment, but every little bit helps.
Also, I bought a turning point prop today, and purchased a hydrofoil to go on the motor the day before that. Supposedly, the hydrofoil helps keep the water more stable, and also helps the boat plane out better. It might be useless, but it was pretty inexpensive at $50.
As for the prop, I bought an aluminum 3-blade 10.75 x 12. I found out that my motor is not a bigfoot, and my gear ratio is 1.83:1 (I called Mercury--who knew?!?!). This prop was recommended to me by the "prop wizard", and is 1" steeper than my current prop (11.6 x 11). The guy at Mercury seemed to be fairly knowledgeable, and told me that going with another inch (I'm currently turning 5600 at WOT) should put me in the recommended range of 5000-5500.
I'm going to install the hydrofoil Thursday, and head up to the lake and do some testing. I'll see if the clean 'toons and foil make a difference. I 'll then install the new prop (I had it 2nd Day Aired to get here Thurs), and see if it makes a difference. My GPS unit is ready and raring to go, and I'll snap some pics of the screen for results. (I actually dropped it in the water getting out of the boat last week, but snatched it right back up--still running!).
With all of the nifty little online calcs, my theoretical speed at 5200 rpm should be 29.1 mph with no slip. I'm keeping my fingers crossed for a slip of less than 38%!!! :-)
Nice pictures but most of them have nothing to do with performance of the boat. However, before we get into that, take a look at the tires on the trailer and get back to us with what the load rating and size are. If they are load range "E" tires, I think that trailer is grossly overloaded as they would be rated for just a tad over 3000# per pair. Don't forget that the weight of the trailer is also carried by the tires so GVW is trailer, boat, fuel, batteries, motor, gear, minus tonque weight. Ok - on to the performance. The prop you have is a pontoon specific prop as it is of the "elephant ear" variety as evidenced by the blade shape. The pitch is also correct for the application but the engine is not. This is a standard leg engine and pontoons should have a Big Foot engine. A Big Foot lower unit carries a 2.31:1 gear ratio while the standard engine carries a 1.83:1. The Big Foot lower unit also runs a bit lower in the water so it less subject to turbulence. That means the Big Foot engine can twist a much larger diameter prop which is essential on a non-planing hull. Props for a Big Foot (actually the entire lower unit) are from the 75 - 90 HP engines and are in the 14 inch diameter range. You have what you have -- don't spend money trying to get blood out of a turnip.
WOW finally found a forum on the subject I was interested in. I have a 16ft Playbouy with a 40 HP Force. I was able to hit 13.2 MPH...LOL from my GPS with the wind at my back.
I now amgetting under 10 MPH, I added some weight to the boat, by adding some wood under the seats to keep stuff off the wet carpet and a third 6 gallon gas tank.
So, anyone with at 16ft Playbouy and a force 40 HP tell me how fast it should really go?
No cavitation, but similiar to earlier post it seems like the last inch or so of throttle does nothing for the speed.
Does choppy water slow it down a lot?
Thanks, steve
You apparently didn't read my post about the Big Foot lower unit but that's fine. Let us know what the foil and new prop accomplish. Don't make any bets on 29 MPH unless someone is towing you. (:-)
Well my force 40 died today just after my first post. Lots of loud noise and pulled the plugs, the lower one has been beaten up badly. I am looking at a new Mercury 40 HP, max rating for my boat. They do not have any big foots available. Will the standard one be OK if I am nit interested in top end speed, just want to get back out fishing. Also any ideas between an Evinrude, Mercurty or Honda?
Silvertip--Sorry... your post came in after I had already ordered the stuff. However, I figured that, in the least, another prop would be good to have on hand just in case. With the hydrofoil, they claim it helps pontoons steer better, and if it does just that I'll be tickled.
As for the pics, you likely just skim posts as I do, but (I think) they all apply to my posts. First, the engine pics are self-explanatory. As for pics of the boat as a whole, I asked above about weight of my boat. I have no idea what the thing weighs, but wanted to see if someone could give me an idea from looking at it. It never crossed my mind about the weight as far as the trailer is concerned, although I did ask my neighbor why they put pontoons on single-wheel axles (he has a 22-footer with a single axle... and no brakes--same as mine). That trailer is obviously made for a 24-foot 'toon, but since I have no idea about the weight I assumed everything was fine. As for the tires, they ARE load range "E"--just checked. Recommendations? I might drive the boat somewhere once or twice a year.
LOL! If I hit 29 mph I'll be ducking--that means a hurricane is blowing behind me! As stated above, my *hope* is to hit 20 mph (thus the reference to 38% slip. From what I've read, 'toons typically have a 20-30% slip--is this correct?). I'm consistently getting 17 mph and hitting 18 mph in calm water with my current setup, and I'm pretty tickled with that. I'm hoping that cleaning the caked-on 'toons and new prop will help me hit 20!!! I'll def post my results.... To be honest, from what everyone has posted here, I'm just hoping I don't *drop* in speed!
Here are some numbers to chew on regarding weight. I have an 18 foot Misty Harbor four-corner fish which is a very light boat as far as pontoons go. It is powered with a 40 HP Suzuki four stroke. The boat weighs 1100# empty. Add an engine (243#) and that makes 1343#. Add two batteries (one troller, one starting), the trolling motor, 18 gallons of fuel, all the fishing gear, and anchor and that adds another roughly 328# for a total of 1661. The trailer weighs 880# for a GVW of a little over 2541. Your boat is six feet longer, has a heavier furniture load and the trailer is longer as well so your rig will be pressing 3000# or possibly even more (larger fuel tank for example). My point is that the tires must be kept at maximum inflation pressure of 90 PSI to support that load. Yes -- you read that right -- 90 PSI (right on the sidewall of the tire). It is probably safe for your use but for high speed highway travel I would be a little nervous.
WOW finally found a forum on the subject I was interested in. I have a 16ft Playbouy with a 40 HP Force. I was able to hit 13.2 MPH...LOL from my GPS with the wind at my back.
I now amgetting under 10 MPH, I added some weight to the boat, by adding some wood under the seats to keep stuff off the wet carpet and a third 6 gallon gas tank.
So, anyone with at 16ft Playbouy and a force 40 HP tell me how fast it should really go?
No cavitation, but similiar to earlier post it seems like the last inch or so of throttle does nothing for the speed.
Does choppy water slow it down a lot?
Thanks, steve
I have a 16'er no name (8' wide) with an 1963 Viking 25hp and I get 15 mph (24 kmh) top speed on it.
Yup--saw the 90 PSI last night when I went to check the tire pressure and my gauge (that goes to 50 psi) went off the charts.
At this point I have little choice but drive the boat back tot he lake (about a 30 min trip on rural roads). Once I drop the boat in the water I'll be able to get something done. Do they have trailer tires with higher ratings? Heck--is a single axle trailer stout enough to carry this boat??
You need to do a very careful summation of the various weights like I showed you, or have the rig weighed at a truck scale. Remember, published pontoon weight does not include and engine since the manufacturer has no idea what engine will ultimately be installed. I'm not aware of a higher load rating for that size tire. Again, for very infrequent use, the setup you have may be adequate. But if you are making longer range trips more frequently, you might consider converting the trailer to a tandem axle in which case you could use tires with a lower load rating (and less expensive) or you might just consider buying a new tandem trailer.
Pontoon Speed Help
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