Water separating fuel filter with drain. Most water separators are capable of continuing to separate water from fuel after they're full, at which point you and I throw them away. I now use this filter on my boat
Racor makes one just like it for more than twice the price. With ethanol in most gas today, which absorbs water, you gotta have this. It fits a standard Mercury/Yamaha "universal" spin-on fuel filter mount.
My '06 90hp Optimax had over $4000 worth of damage last year from ethanol induced water in the fuel. Fortunately it is still under warranty, and cost me nothing to have fixed.
Get this filter. Drain it often.
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Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.
Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!
Currently without a SeaCraft 
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury