I just bought a skeeter bass boat with a 2000 150hp yamaha vmax hpdi on the back of it and I'm doing all the precautionary maintenance stuff like plugs, water pump etc... I also want to do a shock treatment and then start using ringfree on a regular basis. I'm pretty sure that the previous owner has never used ringfree or any other similar products on this motor. What are the dangers of doing the shock treatment and breaking loose all those carbon deposits? Also, I've read that you should change the plugs after the shock treatment because they may become fouled. If I'm changing the plugs before the shock treatment should I change them again after? Any help would be appreciated. Thanks.