I have 2 Magnum 91s, and a 70 4 stroke The 90 have been fantastic. I have over 30 gallons of fuel through tthe one and all i have done to it is adjust the valves and the carb. last year the oldest one just started losing power and needs rebuilt but it does have over 30 gallons of fuel through it. the new'st 91 has been real good also but the 70 really has been junk. i can'nt keep it running or keep the carb adjusted. It just doesn't seem to be any good. The 91's broke in quick and good. the 70 who knows. The ST 2 stroke will be quicker too. I'm sticking with Saito on my big ones.
Good luck