Timing belt m'tnce

[KLAUSMAN]

Hi Team , My cruising cat (Schionning 1320 self build) is fitted with twin 27hp Yanmar diesel outboards,after ten years & 700 hours all is well & I am happy with my choice but have a small problem, obviously it did not take long for the paint to wear off the crank drive cog and the cam cog of the timing belt,so when the boat is idle for a while some powdery rust appears on these cogs.Not good!! So any clues on a spray guaranteed to not harm the toothed rubber belts when left for extended periods.The cautions on all I have read say not to use on rubber ..PS. are the belts rubber or nitrile or what??? Thanks in advance.

[44'cruisingcat]

Maybe lanolin?