Swapped motors - 5hp & 7.5 hp, help

We have 2 GEMs. We bought one with the 5hp and one with the 7.5hp.

We swapped motors to put the 7.5hp into our GEM with doors.

Now the 7.5hp one starts off really slowww … it eventually gets up to speed, but goes like a snail at first.

Is there programming or something that we missed?

Tried to attached pics of the motors, but didn’t work. Please let me know if you have a solution.


I would assume the controllers were programmed differently for the motors and simply swapping them would not be sufficient. If you also swapped the controllers (assuming they are the same model), that would probably work.

Both GEMs are 2005 E4s. When we swapped the motor, we also swapped the converter and controller.

Just noticed the temp light comes on … the wires coming off the 7.5hp motor do not look identical to the 5hp.

Could it be the temp sensor needs to be bypassed?

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We had a completely stock 2002 with the 5 hp motor We would drag race it against our Modified 2002 with R4F 7.5 motor. The stock car could beat the modified car off the line and all the way up to around 23 mph and then the modified car would keep going faster while the stock car would remain the same.

It’s like the program on the modified car had it set up to not allow full power at first so as not to put extra drain on the battery’s

IMO to get the 7.5 motor to Take off as fast as the 5 hp motor I think it uses a bit more power and would draw down your run time. I think by them dialing back the the start off power in the controller they can say “adding the bigger motor dosent effect Milage” I’m sure if range was not a issue you could crank the thing up and it would be quite faster.