Nuvi 500 Boat Mode Hack

"Drive, hike, bike or boat. With the rugged, waterproof, multi-mode nuvi 500, you can do it all. Packed with detailed street and topographic maps, nuvi 500 is ready for adventure both on and off the beaten path. Like the 550, nuvi 500 switches modes to navigate your active lifestyle and provides spoken turn-by-turn directions to your destination."

That is a quote from the product description of the Nuvi 500 taken from the Garmin website. Sounds pretty good, doesn't it? I thought so too, and bought one to replace my trusty but tired Garmin GPS III+ that I've used for nearly ten years on my boat.

A GPSIII+ - best GPS evar! A Nuvi 500 with boating chart - obviously not mine.

Well, it turns out that the Nuvi 500 CAN'T do it all. It will happily let you enter driving, walking, bicycling, and scootering mode, but boating mode is strangely absent from the mode screen. From what I was able to surmise from the Garmin support website, the boating mode is not enabled until a set of 'bluechart' maps is purchased, to the not-so-jaunty tune of about $300 bucks. I didn't pay that much for the GPS!

This struck me as just being silly. I've been using the Garmin "Roads + Recreation" mapset for a decade. It isn't a nautical chart, and it has worked just fine for me. I boat in the Sacramento-San Joaquin River Delta, which can best be described as "a maze of twisty little passages, all alike".

The Delta.  A GPS really helps.

I don't need depth info, its all about ten feet deep at mean tide. I don't need buoy info, there are only two marked river channels anyway. My navigation needs are simple, and the base topo map should work just fine. I just need to know where I am in the maze, how far away the next bar is, and what waypoint to steer for to avoid the shallow spots in the open tracts. I like to know my speed in knots, and I don't want the GPS trying to route my boat over pavement.

After trying three times to talk to someone at Garmin and being on hold for over 30 minutes without speaking to anyone, I sent them this email:

Message Body:
Question #1: I have a nuvi 500 that I use on my boat. I do not have any of the
boating maps, only the base map set that came with the unit. Is there any way to
enable 'boat mode' on the unit without purchasing the bluechart maps? All I'm
looking for is the basic navigation functionality of the boat mode, I understand
that the base maps do not have buoy, depth, or tide info. Question #2: If the
answer to the above question is no, then what is the least expensive boating map
set that covers the Sacramento and San Joaquin rivers in northern California,
and is there a way to evaluate the maps on the nuvi 500 before purchasing them?

To which I received this response:

Subject: Re: enable boat mode?

Dear Jeff,

Thank you for contacting Garmin International. In order to obtain boat on the
Nuvi 500 series you will have to have a marine map of some type in the unit.
Then when you tap the mode icon you will be able to scroll to the bottom of the
list and choose boating. As for the map you will not be able to full view a
screen shot of the coverage area in full detail but I have provided you with a
link that will show you the mapping coverage and the card that will provide you
with area you seek.

Keep in mind that you unit will take the Micro SD card version of this card.

(If you scroll through the list of the chart names you will see that the
Sacramento River is covered, however we do not have coverage of the San Joaquin

I thank you for choosing Garmin and have a nice day.

With Best Regards,
Product Support Specialist
Marine Team
Garmin International

That's not really the answer I was hoping for, but as support responses go, it isn't a bad one. I wish they would have been staffed to answer my call, I wish they could have answered my email in less than two days, but whatever. Tech support is a tough and generally thankless job, don't let anyone tell you anything different. Anyway, the support engineer found me a map that might work for $160 if I was willing to try it sight unseen, but he also gave me a valuable lead- I'd need a "marine map of some type" on the unit to hit boat mode.

On that lead, I went looking for free Garmin compatible maps to try out, in the hope that I might find one of the bay area that would enable boat mode. I found a few sites with free maps. Check out Maps 'n Trails or for some cool topo maps. They even had some maps that claimed to be nautical. The ones I found were certainly of marine areas (the Mediterranean sea, and the coast of Poland for example) but were rendered as standard topographical maps, not as true "marine maps" in the Garmin sense of the term. They would load onto the GPS, but wouldn't enable boat mode. I was not able to find a single map on-line that would enable boat mode on my GPS for the delta.

From From

Finally, I came across the website for a shareware tool called cGPSmapper. It claimed to be able to be able to convert maps from "polish format" into true Garmin marine maps. My hopes were high that if I could find a map of the delta in some electronic format and convert it into polish format, I might be able to use cGPSmapper to load it onto my GPS and enable boat mode. It took me a few hours of searching through maps of California, and for ways of converting the very extensive data available on-line into polish format before I came to a realization that seems obvious enough in hindsight. To enable boat mode, you don't need a map with relevant data for your location, you just need a map with the marine flag set! Well Duh. Seems simple now. CGPSmapper comes with docs for writing a map in the polish format, which I used to create a super-simple marine mapset consisting of just a single point. It turns out that a single point is enough to enable boat mode on the Nuvi 500. Bingo! Problem solved.

Since I've done all of their work, I want to share with you how to enable boat mode on your GPS so that you don't have to speed a weekend figuring out how to do it on your own like I did.

To be clear, the method that I am about to describe to you isn't really a hack, despite the exciting title of this page. It doesn't violate any laws, there is nothing wrong with doing it. It probably won't even void your warranty, but ultimately that is between you and Garmin. Don't try it if you are worried about that, and don't even think about blaming me if you screw something up. Personal Responsibility: Use It.

Enough already... lets get on with it!


  1. Download nuvi500boatmode.img, the nautical mapset that I created.
  2. Plug the nuvi into your computer. It should load a USB disk volume "GARMIN", just like a USB thumb drive would do. Open that volume.
  3. Copy the nuvi500boatmode.img file into the "Garmin" directory on the "GARMIN" volume.
  4. Rename the nuvi500boatmode.img file that you put onto the "Garmin" directory to "gmapsupp.img"
  5. Remove the nuvi from the system and let it reboot.
  6. On the GPS, go to "tools/settings/map/mapinfo" and make sure the "Boat Mode Enabled by Jeff!" map is checked.
  7. Go to the mode screen on the GPS and select boating.

Map enable screen.  You probably won't have US Road & Rec. Scroll down to find boating mode.

Thats it, you're done! Welcome to reasonable marine navigation on your Nuvi.

But what good is it without a chart?

You might think that without a marine chart, the GPS wouldn't be very useful on a boat. Not true at all. Here is what the GPS looks like in driving mode versus boating mode:

Driving Mode - what an interesting route! Boating Mode - MUCH better.

In both cases, I'm trying to navigate across the tract from the south to the north west corner via a waypoint on the safe side of a shoal that I'd really like not to hit again. In driving mode, you can see that the GPS is really freaking out trying to avoid the shoal- it is taking me overland to the south! However, I suspect that its chosen route along the asphalt is going to be worse on my prop than a little underwater mud bank. Also notice that it has put my location up on top of the nearest levy instead of in the slough. At least it chose to put me on top of a nearby 'watering hole' (notice the beer mug icon). I suppose that is not an unreasonable assumption on its part, although I'd rather it didn't show me at at the bar until I actually was.

Now check out boating mode. The most obvious change is that now the display uses a chart color scheme. It isn't a different map- this is the same topo map that came with the GPS, just rendered in standard marine chart colors. Notice that the GPS hasn't jumped my position to the bar. The boat is correctly sitting at the entrance to the slough. The route is going via the waypoints that I requested, speed is in knots, and there are turn, bearing and heading indicators. Perfect!

If the color scheme isn't quite to your liking, you can choose to put the display into 'Night mode' which will make the water look a little more blue. The GPS will even let you view the map in "3D Mode", but I can't say I've ever found that to be a useful thing.

Daytime Nighttime The Titanic Navigating the Delta, now in 3D!

Extra Bonus Goodness

It turns out that the city nav + topo map that comes preinstalled on the unit has tide station information that is enabled when in boat mode! Look under the tools menu for the new "Tides" icon.

Catch the wave - tide info enabled! Nearby tide stations Tide info - cool! Tide info - So that is what those T's mean.


It isn't difficult to enable boat mode on the nuvi 500 once you know how, but Garmin sure doesn't make it easy. I can't say I understand why Garmin chose to disable basic navigation functionality in the unit. I certainly would not have wanted to buy the marine charts from them without having ever been able to preview boat mode at all. Now that I've seen the mode, I am more willing to buy the bluechart maps and try them out. However, my satisfaction as a customer has taken a serious hit from having to jump through these stupid hoops to get the basic advertised functionality working. Maybe after cooling off over the cold, boatless winter months, my opinion of Garmin will recover enough that I'll buy the charts for the start of next season. If I do, I'll update this page with screenshots.

Thanks for reading!

Copyright 2009, Jeff Jahr < >