Most manufactures consider 50 hr average annual use and the filter should be changed annually. With the high humidity here and greater possiblity of water in the I wouldn't go the 100 hr. A $10 filter is a lot cheaper than a motor rebuild. If it's rusty around the edges, it's been on too long.
I would say it depends on the type you have. If you have the one with the clear bottom and you can see HOW MUCH water your separator is filtering then it should be common sense.
I think you enter tournys so run more then most so at a MIN. every 6 months.
If you have the cheap type like stated, $10 ( LOL) then do it every 2 months if you run your boat like I think you would. Heck, you will push 50 hours own your engines per Tourny if you count the pre-fishing.
If I'm not mistaken it cost me $28 per filter for the ones I use, then again my boat has not been on the water in 2 years come May.
One way to tell also is to remove you filter or separator and pour the contents into a MASON jar and let it settle. You will see how much water is in the filter and you make the decision if you should replace it.
I base mine on gallons burned and then do it once before cobia season and once before winter whether they need it or not. 500 gallons per filter is my rule and once a year I change/clean the secondary on the engine and the screen. This year, its time to service injectors too.
Thanks for all the advise. I am still new to boating, and just a weekend recreational fisherman. I changed the filter on the boat shortly after purchasing it in June 2007, I don't think I've put have 100 hrs on the motor since the filter change, but the filter canister is rusty around the rim. I believe the filters are the cheap ones. I'll go ahead and change it out to be safe.
If you have room? Go ahead and replace the filter with a Racor and it's canister. This will make your life much easier.
Fuel tank's develope moisture in them from the change in temperature. This transfers to water. With the site glass you have a quick reference and can drain it off. This can save you maybe $1000 in repair like this fellow has now.