I have a BMW 12hp single
cyl. It came equipped with a paper mesh air filter. I was told I would probably never have to change it in my lifetime (I'm 83 ... there might be a message there) ... As well, both single
cylinder BMW engines (7hp and the 12hp) do not use belts. The alternator
is integral with the flywheel and the water pump is engine driven.
If I had an engine shredding belts - be it automotive or marine - I would seriously be looking at pulley alignment.
Another suggestion I might make for small, single cylinder engines would be to install 'segmented' belts. They run a whole lot smoother and quieter, and can reduce vibration caused by 'belt kink' ... although this probably would not be noticeable with larger engines.
If you are unfamiliar with segmented belts, they are sold "by the foot" and you need to know the width. Sold by Tool Stores and used mainly on table saws and similar power equipment
. I changed them on my HD 5hp cabinet saw ... the difference was dramatic ... very much quieter and no more vibration ... I sometimes leave items on the table saw (not recommended) and they do not move at all.