My first 500cc Runabout Ride

[nhooten]

https://youtu.be/Go5AlMW_eE4Enjoy 😊

[John800]

Do you have any pics of the boat? Specs on it? It looks fun but i am not familiar with that type of racing

[nhooten]

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[nhooten]

This particular class is a 13.5' hull constructed of marine grade plywood and composite materials. We run with the US Title Series (check out www.ustitleseries.net). The series runs many classes reaching speeds of 85-130 mph, most based on bore and stroke from 125cc engines all the way up to 1100cc's in either hydroplane or runabout configuration. I chose to run the 500cc class because I can compete in 500cc, 700cc and 1100cc with the same boat and motor. As you can see in the above photos 1100cc requires that there be a driver and a rider. We run Koenig or the copy which they call a Konny as the Koenig is no longer in production. Check out http://www.konny.cz/ for more details on the engines. One of the most unique aspects of this type of racing is we have a variable length exhaust. As you are going around the course you are full throttle and can pull a lever to shorten the exhaust and create more back pressure. It's akin to hitting a nitrous button. If you pull the pipe too soon or too quickly you risk damaging the motor as pictured above. I hope I answered your questions and if not please don't hesitate to ask away. If you are looking for more information about grass roots outboard racing I highly recommend hydroracer.net. Come out and watch a race! You will find that the racers and crew are very friendly and eager to help you obtain a rig if you wish to race.

Thanks,
Nick

[John800]

What is the pipe configuration? 2 2 into 1s or seperate pipes? Thats pretty cool. What changes on the pipe? Shorten a center section somehow?

[nhooten]

The pipe setup on this motor is 2 into 1. The Rossi and Vrp motors have a dedicated pipe for each cylinder. As for the pipes the whole pipe slides on the header. About 6 inches overall.

[John800]

The pipe setup on this motor is 2 into 1. The Rossi and Vrp motors have a dedicated pipe for each cylinder. As for the pipes the whole pipe slides on the header. About 6 inches overall.
The 2 strokes i have been around and modded have been snowmobile motors. I have known some guys that had all kinds of mod motors both race and trail and have never heard of a pipe like that, variable exhaust ports are on almost all sled motors, but never seen a varible pipe. If you have any good pics of the pipe setup handy i would be interested to see it, saw a few from a distance in the pics section of the sactioning body website you posted, that is interesting to me to say the least.

[nhooten]

The reason we use the sliding pipes is due to the fact that we have a fixed gear ratio. I'm a Florida boy and I don't think I have ever laid eyes on a sled but I'm assuming you have some sort of belt drive like a CVT. It allows you stay in the powerband whereas we have to start out with low back pressure (relatively) and raise it by pulling the pipe once the motor is spinning at the appropriate RPM. I will do some digging and see what I have photo/video wise.

[nhooten]

Here is an example of a 125cc Runabout pipe setup. This is a Rossi engine I believe


https://youtu.be/HrjNOQyw030