RCU Review: AquaCraft RIO 51

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    Contributed by: Matt Gunn | Published: February 2008 | Views: 118564 | email icon Email this Article | PDFpdf icon
    Rio 51

    Review by: Matt Gunn (webdr)
    Driver: Will Nichols (Believe It)

    Rio 51
    Distributed exclusively by:
    Great Planes Model Distributors
    P.O. Box 902
    Champaign, IL 61826-9021

    Website: www.aquacraftmodels.com

    See the Rio 51 in action!

    Dialup 13.3mb

    Broadband 18mb


    Large-scale gas performance

    FM radio

    Hull handles rough water with ease

    Grimracer anodized running gear

    Longer run times than electric or nitro

    Header prone to cracking *updated header currently under development*

    Gas tank cap leaks gas

    There's something to be said about large scale gas powered boats; the sound, the performance, the smell, the whole experience of operating one at speeds that rival their full-scale counterparts brings a smile to your face. And up until recently, you had to piece together a gasser, ordering parts from a number of different manufacturers and assembling the running gear, installing the motor and hardware, only to discover your in for over a grand, any you haven't even spilled any gas on your shoes! The whole process was something you learned from experience rather than a set of instructions.

    But in the past few years, ready-to-run gas boats have hit the water hard with the majority of them putting down some pretty impressive numbers out the box. Their appeal not only comes from decent performance but that they are truly ready-to-run; you don't have to buy anything except for fuel and oil to have hours of fun on the lake or in the river.

    Enter Aquacraft Models, a company with some well known nitro and fast-electric hulls that recognizes the desire for large, high-performance rtr gas boats. And their answer is the Rio 51. This large scale gas mono is an exceptional choice for the budding boater, the person looking to make the switch from nitro or electric, or anyone wanting the gas experience without paying the full price.

    The Rio 51 was tested by myself, as well as a seasoned racer, and a total newbie in an attempt to gauge the boat's good and bad characteristics from different standpoints. Now, let's mix up some fuel and test the Rio 51!

    Name: Rio 51
    Price: $699.99 retail price
    Length: 51" bow to stern
    Beam: 13.5"

    Motor: Fuji-Imvac BT-28
    Weight: 13.75 lb
    Receiver batteries used: NiMH hump pack (not included)
    Transmitter batteries used: 8 AA batteries
    Radio equipment: (Included) Tactic 2-channel FM transmitter, receiver, throttle and high-torque steering servo.

    • Flat head screw driver
    • Gasoline and 2-stroke oil mixed @ 32:1
    • Marine grease
    • 12 AA batteries

    Other Helpful Items

    • Gasoline-safe fuel container and pump
    • CorrosionX anti-corrosion spray
    • Hex-head wrenches for running gear adjustments

    Five air scoops
    Main scoop and engine head
    Hatch fasteners
    Running gear
    Trim tabs and adjustable surface drive
    Rudder and water pickup

    The Rio 51 arrived at my door in a massive box that seemed to take up half the living room. Even the dog was a little upset as this cardboard behemoth invaded his favorite sleeping spot on the carpet. I suggest opening it on the front lawn to keep your significant other happy and the neighbors jealous. After chucking the shipping box, your presented with yet another cardboard monstrosity, it's contents proudly displayed in ink all over; make no mistake, this boat is big. Pull the top off and you'll see the Rio nestled in enough styrofoam to build a floating dock. The radio is in it's own box tightly secured to prevent movement. I have a feeling that even the roughest shipping company would have problems damaging this hull! Before you throw all that packing away, cut a fist-sized square of styrofoam and save it; you can then glue it to the bottom of the hatch, effectively preventing the hatch from sinking if it comes off in the water. Nice, huh?

    Starting at the stern, Aquacraft has given the Rio 51 black anodized Grimracer running gear, thanks in part to designer Michael Zaborowski. On either side of the transom are cnc-machined turn fins that can pivot back if they hit something. They are fairly sharp and their fit and finish is excellent. Slightly inboard of the fins are the trim tabs. They are made of stainless steel and are adjusted by bending them up or down. It takes some force to bend them so you don't have to worry about them moving without you applying the force. Exiting out the back of the boat, and slightly offset to the right, is the black anodized aluminum surface drive. It's drive angle is adjusted up and down by loosening the two hex-head screws. This system is stout and makes for easy flexshaft maintenance because only two screws need to be loosened to remove it. As with the fins, the finish is perfect with no blemishes found anywhere. Coming stock with the boat, and located at the end of the drive, is a two-blade cast prop made of copper-beryllium-titanium. It's a great-performing prop to get you in the water and an optional three-blade prop (pictured below) is available for even greater performance. The rudder, like the rest of the gear, is anodized and quite sharp. It is held in place by a hex head screw above a smaller phillips head screw. The smaller screw is designed to shear if you strike something, thus saving the hull from severe damage. It's also adjustable so you can tuck it in to keep the hull planted when turning. Forward of the rudder is the coolant pickup. This is where all the water is picked up for cooling the engine and exhaust and it does a good job of doing so. Make sure it is lower than the trim tab of optimal water pickup.

    It should be noted that Aquacraft has chosen to secure the running gear to the transom with metal plates vs blind nuts. It looks as if these plates are very strong and should be that added bit of strength to prevent anything from cracking the glasswork.

    Examining the hull itself, you'll see the Aquacraft team has gone to great lengths to create a high performance, as well as visually appealing final product. The lines are great, the graphics look good, and it handles a variety of water conditions extremely well. Starting with the colors; your given a pallet of red, blue, or yellow which sets the boats apart if you are running more than one. The graphics consist of yellow, white, and black checkered flags towards the rear and a few yellow "Rio 51" labels on either side and on the deck. A decal sheet is included with a side-specific number plate and numbers, Aquacraft logos, and a few Grimracer logos as well. All of them look good on the hull but are a little thin and the underlying hull color can be seen through them; this made the white color on my checkered flag look almost pink. Was this a problem? Not really, just worth noting. Aquacraft has made sure the engine stays relatively cool by adding a total of five air scoops on top of the hatch. These scoops coupled with the engine and exhaust coolers do a good job of keeping everything from overheating. The hatch is attached with a dowel up front and two fasteners at the rear. It's secured by positioning them parallel to the hull and pressing down, and released by turning them 90 degrees. The fiberglass work on the hull is quite thick and there were a few guys at the lake that were interested in testing it's strength; they pulled it and pushed it with just enough force to satisfy their curiosity.

    Turn fin
    Optional 3-blade prop
    Coolant exit
    Component layout
    Gas tank
    Flexshaft oiling system
    Engine and header
    Walbro 257 carb
    Pull start

    Aquacraft chose to outfit the Rio 51 with a Fuji-Imvac BT28 marine engine. It's a water cooled 28cc 2-stroke with enough power to swing the large props available for the Rio and push it into the low 40s. The motor is secured to the hull by four rubber isolators that reduce vibration and the twisting caused by torque. Starting the Fuji is accomplished with a pull starter similar to any trimmer or blower and the system worked as expected throughout testing. The carb is a standard Walbro 257 with a manual choke and features a high speed and low speed needle. Information pertaining to tuning the carburetor is included with the Rio and is explained in plain english for all you first-time gas boaters. The Fuji is cooled by a water jacket on the head, exhaust flange, and at the base of the tuned pipe. Water is picked up at the rear and pushed forward to the head, then to the base of the header, then to the pipe, and is expelled out the left side of the hull. Keep in mind there is no water pump because the forward motion of the boat pushes water through the system starting at the pickup tube.

    Exhaust is expelled from the engine through a "wrap-forward" style header common on deep vee hulls. The tuned pipe slides over the header and is held snugly with two o-rings that prevent it from moving around and keeps the cooling water from entering the pipe. The pipe exits the hull at the transom which is fitted with a flanged rubber tube to reduce vibrations and prevent any damage to the hull. The header is made of stainless steel and has proven to be the one weak link in the Rio 51's outstanding setup. Mine cracked at the base after a few tanks of running. This problem has manifested itself on a few other boats and Aquacraft has taken the steps to redesign the header. A new and improved header is being manufactured as I type and should be available very soon, so I've been told. The tuned pipe as dubbed a "quiet pipe" and effectively keeps the decibels down around 80db which shouldn't cause too much static with the neighbors ...notice I said "shouldn't."

    The gas tank on the Rio is a hard plastic tank with a screw on cap. The cap has a small hole in the top for ventilation.  I found after long runs the breather hole on top of the cap is allowing gasoline to exit the tank.   It's not much, but after a long run you'll see a thin coating of fuel on top.  I installed a standard fuel nipple and fuel tubing to the top of the cap which I hoped would allow ventilation and stop the fuel from escaping.  Unfortunately, the problem is with the cap itself as it does not have a gasket to seal it completely tight.  I will be looking for gasket that fits the cap and is resistant to fuel to solve this concern.

    Below and in front of the gas tank is the oil injection tank for the flexshaft. This is a great little feature that allows for a constant flow of motor-oil to the flexshaft for lubrication. There's a hose clamp on the line for cutting the flow of oil when your Rio is in dry-dock. Take note; the auto-oiler is in no way a substitution for lubing the flexshaft with marine grease.


    No blind nuts
    Radio box, receiver and servos
    FM radio

    The electronics included with the Rio 51 are decent; you get an FM pistol-grip radio, a standard throttle servo and a high-torque steering servo, and an FM receiver. The switch is mounted in the radio box lid and is waterproof. Also included is a battery clip that accommodated 4 AA batteries to power the servos but I chose to use a rechargeable NiMH hump pack for longer run times. The transmitter features servo reversing, trim, and steering dual-rate. and there's also a red LED on/off light that will blink when battery level gets low. My only issue is the lack of a charging jack, which limits the transmitter to non-rechargeable AA batteries.

    The radio box made of hard plastic and does a great job of protecting the radio gear. The lid, though, is nearly impossible to remove without a screwdriver or something similar to pry off the clip. Not really a problem but it snapped my finger once trying to remove it by hand and left a nice mark ...I wont do that again! Radio box seals are used where the pushrods enter the box. I experienced no problems from the entire FM system and expect it to last for a long time, even with the constant vibrations handed out by the engine.

    The engine must be broken in like any nitro engine. The BT-28 is set very rich from the factory and some needle adjustment might be needed to get it fired up, depending on your location and outside temperature. Per the instructions in the manual, run the Rio through a full tank of gas at a somewhat rich setting before tuning for performance. But before you crank her up, prepare the boat by adding 4 AA batteries to power the receiver and servos and 8 AA batteries to the transmitter. Don't forget to fill the auto-oiler with motor oil and grease the flexshaft. There's a green clip on the oiler tube that should be clamped closed before you put any oil in it.

    Fellow AMB and RCU member Will Nichols (Believe It) met me at the Atlanta Model Boater's lake to test the Rio 51. Right from the start, things went smoothly; the green clip on the flexshaft oiler was opened to allow flow to the shaft and after a few priming pulls with the spark plug cap off, the engine sputtered to life and required a little throttle trim to stay running. With the needle settings remaining untouched from the factory, it was evident that the motor was running too rich as we tossed the hull into the water for break-in. A little leaning of the high-speed needle got the Rio almost on the pipe and we proceeded to finish break-in.

    Once the Rio 51 is broken-in and tuned for performance, you'll soon realize that it's a great hull and exhibits no adverse handling characteristics. Will put the Rio through the ringer but was unable to capsize the hull, but don't think it's invincible; introduce some heavy chop and you could get it to grab in a turn and roll. Full speed left and right hand turns are possible, as evident in the video, and make for a nice show as it digs in and throws a few buckets of water. Even though left hand turns are easily accomplished, the Rio 51 does best when turning right due to the placement of the rudder and the counter-clockwise rotation of the propeller. Although we were in a small lake, we were able to make some decent wake by running in a circle, creating a washing machine effect in the middle. Hitting this wake almost always got the Rio 51 airborne and it repeatedly landed smoothly and kept on going. As far as attitude, the Rio 51 was close to perfect from the factory. I added a slight bit of positive angle to the surface drive and maybe 1 degree of positive to the trim tabs to pull the hull out the water up front. In my opinion, this seemed to wake the hull up a little and got it moving well.

    The Fuji-Imvac BT28 motor supplies the Rio with enough power for the new gas-boat enthusiast, or anyone just looking for high-performance boating. It provides speeds around 40 mph with the optional 3 blade prop which is just fast enough so you don't have to worry about it getting ahead of you. Throttle response is crisp with no lag and the torque is sufficient. The exhaust note is not as sharp as an aluminum tuned pipe, it's definitely more mellow and should allow you to run in public lakes but remember to always respect others when running your boat in public; what's music to you may not be so with others.

    The only problem I encountered with the Rio 51 was the stock header. The weld around the flange is weak and prone to cracking as did mine only after 2 tanks worth of running. I'm pretty sure the vibrations, weight of the pipe, and the weak welds all played their parts in killing the header. Note that Aquacraft is fully aware of the problem and is taking the steps to correct it. After contacting them about the casualty, I had a new header at my door in a few days.

    A couple of things to watch when running your Rio 51; Always make sure there is water exiting from the coolant port on the left side of the hull and get in a habit of looking for it every pass. Doing so will ensure adequate cooling and will keep the Fuji happy. Also keep in mind that even though the Rio is fitted with a flexshaft oiler, remove the flexshaft after one or two sessions and re grease the shaft. Last, charge or replace the receiver batteries after every session to ensure a happy experience next time out. This is where a receiver pack makes sense.

    See the Rio 51 in action!

    Dialup 13.3mb

    Broadband 18mb

    The Rio 51 is a great entry level gas boat that exhibits exceptional performance for it's class. The hardware and hull are top notch and the engine is a good mix of economy and power. Aquacraft also gets an A+ for an easy to read instruction manual that guides you through break-in and tuning as well as maintaining your Rio 51. Although the test boat suffered from a broken header, I feel that once Aquacraft gets the new design out, the Rio will be a flawless boat for the beginner or anyone looking for real gas power at a price that wont break the bank.

    Aquacraft Models/ Great Planes Model Distributors
    P.O. Box 902
    Champaign, IL 61826-9021

    Web Site: www.aquacraftmodels.com

    Atlanta Model Boaters
    1000 Naturally Fresh Blvd.
    Atlanta, GA
    Web Site: www.atlantamodelboaters.com

    Thanks to Will Nichols (Believe It) for helping me test the Rio 51.

    Comments on RCU Review: AquaCraft RIO 51

    Posted by: Dreamin Hemi on 02/24/2008
    Great video! I had the same exact experiences with my Rio 51. Great boat, expecially for the price...got mine for $610 through my local hobby shop!
    Posted by: Justaddwata on 02/28/2008
    Awesome effort!! Very well written review with good balance of information and opinion. Well detailed pictures also. I am too very impressed by all I have seen with my Rios so far (though no time in the water as yet). Details like the reinforced plates behind transom hardware is a feature that even the top of the line guys might consider. To see such a well thought out hardware package in a boat in this price range and the level of quality makes this boat a steal in my opinion.
    Posted by: GEEZERRC on 08/11/2008
    Posted by: webdr on 09/12/2010
    Thanks guys. Im still loving the Rio after two and a half years of playing with it. Done a few mods such as switching to a zen, but overall its been a blast. Ive been into helis alot lately. check out the pics at www.gunnphotoservices.com
    Page: 1
    The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.

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