I bought a handheld gps a few years ago and bought a lakemaaster chip for it which cost as much as the GPS unit (lowrance outback), $100. I didn’t like the idea of paying so much but it was something I couldn’t do without, being a great map with contour lines and wingdams.
This year I finally joined the crowd and bought GPS for my boat, a lowrance E5. The chip. I liked it so much I bought another one but found the lakemaster had been bought out by johnson outbopard who own hummingbird gps and they cut off lowrance. Now lowrance was selling different brand maps and I found weren’t near as good as lakemaster. So I looked and looked for weeks and finally found one on ebay for half what I paid before so that worked out good for me. You can still get the older ones if you look hard enough. Now I have identical gps in front and back of the boat and I can share waypoints on both.