I am new to the gas hobby, although I have been flying nitro for years. I am building a Ryobi 31 cc, and a Homelite 25 cc, both to be used to drive a 40\" crackerbox of my own design. I need to know where to begin with the prop and drive. An engineer friend of mine is helping me design water cooled heads for kicks, and if all goes well my first project crackerbox should be running in August.

Regards, Dogg

First off, Welcome to MGB Ray.

Using the engines you are, in an unknown hull, your not giving us much to relate too.

Most likely your prop requirements will follow fairly close what we use with Zenoah or CY power. Staying with easy too access props that are not that costly, would say Octura X467 or X470 .... Prather 270 or 275 would be a good starting point.

Scott, thanks for the tip. When I began building my first boat from scratch, I soon realised that I was somewhat clueless and way out of my league... I have since obtained plans and built up a light and pretty 50\" crackerbox. I have also modified several engines- 3) Homelite 25cc's with water jacket and mild porting as described on the mod webpage, 1) 41 cc mac with water cooling only, and a few Ryobi's with water cooling set up to run gas/glow with machined brass flywheels for electric starting (the joys of autocad). A friend and I also built up a really cool 1 piece mount out of 7075-T6 for the Ryobi just to see if we could do it, and we are working on a new set of mounts for the Mac. So back to the boat: If I am running the modified Homlite with a big bore carb and pipe, can I still get away with using the X467 or the x470 prop?

How about some pics of your home made mounts. 7075 is a strong aluminum, but will it stand the vibration of these engines without fracturing? Perhaps a better choice would have been 7050 or 2024.

I tend to use whatever scrap is available...I will get some pictures together.


Dogg