I have an 8' Bombard (made by Zodiac) that I use with a 2 hp Honda outboard. The little Honda will run almost 2 hours at 3-4 mph on a 1 liter tank of gas. The boat weighs about 50 lb, the motor about 30 lb so it's not difficult to move around. Haven't had to patch any leaks so far.
We went to San Blas, Mexico for Christmas 2007 and spent hours exploring the estuary bird watching. Saw numerous crocodiles too.
Last February we went to Kino Bay, Mexico and explored Isla Alcatraz, a small island in the Golf of California about a mile off shore, spotted two whale carcasses on the far side.
We've gone upstream on the Colorado River from Lee's Ferry in Arizona, and on the Rio Grande (aka Rio Bravo del Norte) at the Big Bend national Park in Texas.