Hey I have A GEn1 (pretty sure) HDS5 NAutic instight. Its on my big jetboat. I Run A big glacier fed river for 30 miles and it is invaluable in getting through the many miles of silty sandbars of the 1 mile wide river.

My gps has A lag. when turning back and forth at warp5 jetboat speed it cant keep up with my direction. I have the POINT1 external antenna and its 7-10 satelllites withen seconds of power up. Also I believe this antenna was made for newer model Lawrance products but it also replaces the discontinued LGC 4000 that was originally the external antenna for my unit. ( I think). I also did the most recent software update on it 3 months ago.

I have it mounted about 12 inches above my hardtop on a pole. I also have the GPS ping speed/refresh speed set to highest level on the gps.
I was using it without external antenna and thought that was the problem. But there was very minimal change in the lag with the antenna install. The only difference I noticed was it gets several satellites instantly instead taking 5 minutes to get hooked up to outerspace. But that being said it is very accurate and my tracks are always reliable and accurate run after run. I have about 15 50 mile river trips this year and my gps trail are all spot on to the last when navigating the river.

Now just for reference my friend and I have the same boat 25ft Thunderjet hardtop and we run the same river (Taku) and take the same routs. Our cabins are right next to each other.
He has the older "Elite" model 4.5 inch screen with external antenna and he just got a new HDS7 with just the internal antenna. They are side by side on his dash. He says both of them keep up in his fast turns. He says both will be behind for just a moment when making a hard turn but they do keep up with his boat. My Unit will take about 5 seconds to straighten out and get lined up again and that can get me into trouble if I try to count on it. We don't navigate soley by gps but they help out a lot where the river is wide and the water is high and sandbars are hidden. And sometimes when the fog is thick for miles and I do count on it to get through the foggy days.

Next spring im getting the New hds 7 touch screen But there shouldn't be any real reason im having trouble with my HDS5.

Thanks for help.