I traced mine to a dead hooker I left in with the boat covered and the sun bearing down.
I usually rinse out the ski locker about once a month with lake water, and before covering for storage, I open the hatch and other lockers to allow them to air out. I'm sure there is a myriad of cleaners available that these guys should chime in about, but I couldn't pass up a dead hooker story!
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Walt B
"Debt-Charged"Black '07 H210SS6.2L Bravo One turning a 21P HIFive
Wakeboard Tower with Perfect Pass Stargazer version
Missouri River; Kansas City, Mo.