This is all excellent advice....use the Bob until you are more proficient at righting your boat. However, I would also highly recommend sealing your mast. It concerns me that your boat is turtling so fast and you are unable to un-turtle it without the assist of a power boat. If feasible, take your mast down to a body of water and submerse it to see where there may be leaks. 3M makes a sealant specifically for marine use and is very easy to use. If the body of water isn't close, seal around all fixtures on the mast including all rivets. If your mast is filling with water, it truly will require a power boat to right.
At 200 lbs, I can solo right my 18 and my wife and I can right our very quickly......under two minutes. Actually, under 30 seconds once she gets off the top hull
. While she is clambering down to the bottom hull, I get on the daggerboard to help prevent turtling.
While the Bob is an excellent choice, I would also seal the mast....that way you're set both ways!