Good to see another apollo owner, not many of us out there. Unfortunately, my apollo has an outboard motor so the belt is different. However, if you have the old belt, measure the length and the width, and thickness and then you can probably find the belt size or one that is slightly smaller. i have used several companies trying to replace belts over the years.
http://www.ceitron.com/passive/flatMbelt.html
http://www.studiosoundelectronics.com/belts.htm#FLAT
Here are a couple i have had success with.
oilmanmojo