I use a streetpilotIII for driving and the Garmin V for the boat takes bluecharts but is hard to read compared to the 182c

How about a 182C mounted on the right side on a bracket?

I want to keep the dash clean. I was thinking of going with a hand held 176 and resting it on the right side above the stereo remote.

One of the guys at my marina mounted a 182 with the internal antenna on the dash of his Black Thunder and loves it. Easy install, and worked right away, first time. Garmin's software and controls are pretty easy to use. (Important for those who don't believe in owners manuals, or even quickstart guides. Like men.) Like Ted said, any speedo or other device that will take an NMEA 0183 input can share the signal.

I went with the 2010C - the GPS equivalent of a wide-screen TV. That thing is no less than a-w-e-s-o-m-e. I made a plexiglas housing and mounted it over the cabin door on the dash of my 382. (Sorry - no pictures right now.)

GARMIN MAP-188C
get a sounder too :D

Macklin,
I don't have a pic, but I also did not want to mod the dash. I lifed my compass out, and ran the power wire to my Garmin Handheld down to my power panel. I then re-installed the compass, and left the power cable through the hole, and out the back. I took some very pliable bathroom grade white silicone and sealed the lift at the rear of the compass bezel.
WestMarine has a 3M product which is basically a sticky-back plastic velco. It is VERY sturdy, and holds the base mount for my handheld GPS on the top of my dash in my Sonic. It all looks very clean. My handheld is completely removable; including the bracket, and I have kept everything original and intact on my dash. It works very well. I think you could do the same with either lifting the edge of your dash panel, or removing a screw, and inserting your power wire though that hole, and silicone it back sealed.
When/if I want to go back to original, I just need to remove that little bit of silicone, and pull out my hard-wire powercord. The sticky-back velco will come off with a little WD-40.
You definately want to have a DC cord powered GPS, because if you rely on your battery handheld, I guarantee the time it dies on you, is dead of night, with no fricking moon.

internal antenna
 

I have a 182C in my 38 Top Gun with the antenna mounted in the forward compartment(the other side of the "cigarette" mirror). No problems. Works great.

Going to install an antenna in the cat as well and use the same GPS.

The 182C is the best I have seen. I have two Garmin GPS's in my plane. Hard to believe we used to fly without them.

No pics and the boat is shrink wrapped for the winter. a ram mount is basicly a mount with a ball joint where it attaches to the dash and another where it attaches to the GPS mount. This makes it very adjustable. I had an extra mount in my old Suburban and would load the street and road data in it and use it also on long car trips. Do a Google search and you should find their web site.

I have a 182C with an external antenna. use a RAM mounting arm that swivels. Works great. The internal antenna gave fine reception but did not work with the swivel mount.

New 196
 

Garmin has just released the new 196 (portable). Is not color as the 182C but has Land, Sea and Air capabilities(snowmobile as well).

6 AA's or cigarette lighter cpability.