ezgo 92 marathon w/ curtis 1204 wont move what do i check first, order of eliminatin?

[buggysean]

update - i said curtis 1204 b/c thats what i saw i adiagram yesterday, but i saw this here http://www.vintagegolfcartparts.com/...=100013&Page=1 copy and paste that it says "solid state speed controller" any way i have exactly whats in this diagram...
. Plz help...i have been reading, you guys know your stuff...
i am a cart rookie and need knowledgable help bad...i bought an ez go 3 wheel model that works...and I bought a ez go marathon 92 that is a 4 wheeler. with hopes of gettin the marathon going and using the 3 wheeler as parts(mainly for the batterys...) I say marathon b/c the serial number plate was under the glove box not in it... (a site said that meant marathon) last 2 digits on plate is 92(site said last 2 were year of cart)...
so I took the batterys out of the 3 wheel model and put them in the 4 wheeler... it wont move...all the wired are exactly like the diagram in link above... so i am taking it the 4 wheeler has a bad part??? please tell me what to check first, how, where, then order of elimination after that...
if i can figure out whats broken, i can replace it....
i am mechanically inclined, have a tester, tools, just need some GUIDANCE... i have never been around carts but am a quick learner if someone has a minute to help me.

thanks ahead of time