I had the same 'ticks' last year so I went and got a killer spray for boats. It's almost odorless but the beauty of it is that it doesn't go on wet. It comes in a can and I use it on my boat all the time to keep off the spiders. A light treatment 1-2 a month is all I need to do and it hasn't affected the finish in any way. You can see it here:
I'd say a can should treat your boat at least twice. I like to spray it up under my bimini and around the railing, up under the swim platform and anywhere the webs form.
Since we are talking spiders. I have found the wonder spray for spiders. Great on your dock/boat/house or whatever. Its called SpiderNot. Its about $9 per can. I spray my whole dock with one can. It usually keeps it clean for about 1 month.
I was out Tuesday Evening May 25th...... Saw the same thing.... atleast 5 ticks crawling inside my boat. 2 or 3 on my arms. Not sure what that was about.