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I am in the process of selling a nice 25XS and the purchaser would like to have a prop for this engine. He will be using the engine on a Jupiter hydro which weighs about 140 pounds and with him ready to go weighing about 230 plus the engine. My question what would be a good place to start with for a propeller. I assume a three bladed prop but what diameter and pitch.
Thanks
David
David that is going to be a very light total rig for a 25XS at 230 plus engine:eek:. The driver is 90 lbs based on your numbers. I guess 340 - 350 with engine, fuel jacket, helmut etc. .still light.
I suspect this rig to run at about 70 if the old Jupiter design can deal with that speed and the 25XS engine. If this is the 9'-10" Jupiter it was Kelly's B hydro design that ran well with the toilet bowl 20H. On the Wetback 9'-10" I raced with the 25SS engine with 16:21 gears I ran a 7 x 12" pitch at 7000 rpm in the 63mph range. I do not have the 25XS but knowing that it has more HP than the SS and assuming 16:21 gears I would start with a 13.5" pitch x 7" diameter. Testing will determine if that gives the desired rpm at the proper height and angle. From there its either more or less pitch or maybe some trim some of the diameter to loosen it up
Some of you 25XS drivers need to chime in here to give actual props you are using.
Pete