Had a problem with my iWAY 350C shutting off after about a half hour of  operation in hot weather.  Unit is mounted on a RAM handlebar mount.  Others here noted the same problem.  Some linked it to heat, others to vibration.    
I contacted Lowrance and sent them copies of the messages on this board showing others had had similar problems.  Got a return authorization even though my unit had been out of warranty a few months.  They received it and sent a note back saying they'd send it to engineering for test and evaluation.  I responded thanking them for their offer but asked them to send it back "as is" and I would limit its use to my truck and get a specific unit for motorcycles (the iWAY is not weather proof).   
The next thing in this sequence is a new 350C was delivered by UPS--no charge.  Of course, I can't verify the malady is fixed until hot weather arrives, but just wanted to post this note to let everyone know what a great customer service operation Lowrance is.   
If you're having problems with their products, I highly recommend you contact them.  Nothing to lose except a few minutes at the keyboard or on the phone.