I have a Magnum 52 four stroke that came on a 4* that I bought. I've been very happy with it. It runs reliably, and pulls great vertical lines with an 11 X 5 prop.

I have had one problem with it. The small metal tab that keeps the high speed needle valve in position broke off (not from abuse, I rarely touch the needle once it's set), but all I had to do was slide a piece of fuel tubing over it and it's been fine.

I have an OS 70, and a YS 91 AC, they're both very good, very reliable engines, but for the price I wouldn't hesitate to buy another Magnum four stroke.
Dennis-