I have a Garmin 240 and suggest you get a different brand.

It worked great, I used it 4 times and parked the boat in the garage for the winter.

I got the boat out again for the 4th of July weekend and the 240 would not work. I sent it to Garmin along with all the receipts showing date of purchase, and the $79. check to fix it in case they would not do it under warranty (it was 13 months old and the warranty was 12 months) . I got a new 240 back, with the note the old one had internal damage and no check returned..

They charged me to repair it, even though it had almost no usage time and was only one month past the warranty period.

I suggest you buy some other brand besides Garmin.