have a seadoo XP, 1996 800cc model.

It came with a non-branded battery (12v 19mAh) - after starting the Ski a few times, All it does is beep... if i leave the ski for a while, it will turn it over again.
with the ski in water, it really struggles to start!!! I've found a 30mAh battery that will just about fit in the tray. Will a 30mAh battery damage any systems?

Idle when out of water seems fine.... around the same sort of speed as a motorbike, in water however the ski will NOT tick over. also seems to choke up easy if left on idle (out of water) for 30 seconds or more.

Any help with the above would be appreciated!