Regarding getting through the grass with an under-powered motor there are a couple options. One is the "salad shooter" method where you partially lift the motor out of the water except for the motor body and the blades, hold it with your hand, and then chop through just the top layer of grass. This avoids grass tangling around the motor shaft. It is however, very noisy. A second option is not to use the TM. Pull the engine out of the water and use a push pole--very quiet, but you can't fish and push at the same time--and you have to move constantly from the bow to the back. It is a good method for punching mats (which is a grass fishing technique that works well starting now, and lasts through the summer).
Your last option is to buy a TM with more power--that's what I plan to do when my current 55lb finally dies.