Hello all, my 70 hp johnson outboard it working great when I'm not pulling anything. However, when I was pulling a tube the other day it bogged right down. I took the tube off and was able to go top speed. I was pulling a 80 pound child so not a big load but it still bogged down. What would cause this to happen? I have a 17 foot bowrider so wondering why this would happen. Any insight would be appreciated. Thanks