Water Cooling CMB 21 Greenhead

[TonyKilbarger]

I have this engine in a Jag 2 21 sized rigger. When I run it, I can grab the head right after a run and it is not really past warm. I have seen several people who block off the water outlet and then drill the jacket on top for water out. My question is how big should the output hole be? I seem to remember seeing .040 or .050. I am running a standard tidewater rudder and currently stock water fittings. Last season I had the waterline pop off during a run and the boat seemed to go faster as it got warmer. Runing a CMB TT pipe and best with an H5 ABC prop. Any input would be appreciated.

Tony K.

 

[Wally Marsh]

Hey Tony

I've played with a .21 Jag II/CMB greenhead .21 combo for the past 5 years. It's now in "retirement' now since I am building the Blackbird .21 hydro with Chris and Steve wood. You will want to block off the water outlet of the jacket with a set screw, then drill out a new .052" (#55 bit) hole through the top. All nitro motors need the proper heat to run their best, even more critical with the .21 motors. I restrict the water even more in the spring and fall with an adjustable collar on the water line. Make sure the pick up scoop on the rudder extends all the way to the leading edge, correct with a round file if not.

I've made some modifications to the hull and set-up improvements with my Jag, if interested I can PM you with the details, or give me a call 515-964-0475.

the Wallster