36" tunnel would be more in the line of 7.5 nitro or Q class for electric. TT only made a 3.5, which I don't know if they are still in production. Don't know if the 1515 would be enough for a 36". I plan on putting a 1515 2200kv on my PX-300 (30") this year. Some races appear to be getting rid of the P-LTD and going straight P. Also want to see what my boat will do for the IMPBA 2 lap 1/3 mile record.