I doubt this was necessarily any real inspiration for MacGyver, but I ran across an interesting page about a short-lived (but apparently pretty popular) TV series from the early 1960s called "It's a Man's World".
http://www.tvobscurities.com/articles/itsamansworld.php
It also featured the main character living on a houseboat, along with roommates. The premise of the show is nothing like MacGyver, but it is an example of earlier shows featuring characters living on a houseboat. It includes video clips and pictures- just thought it might be of interest.

(And by the way, offhand there's only a few other shows I can think of with houseboats- the primary ones that come to mind are Simon & Simon and Riptide)

In Austria, we also had a series on tv where the main characters lived on a houseboat for some weeks during their holidays.
It was "Die Knickerbockerbande" (books for children by Thomas Brezina), featuring 4 children who solve crimes.
The houseboat was at an Austrian lake ("Neusiedler Lake"), surrounded by reed. A very silent, idyllic place miles from anywhere. Just where kids like to go for vacation

I was doing some looking around online just to see if the houseboat does still exist and I found the houseboat that Rock found on GoogleEarth. Here's the link:
Houseboat
It reminds me of Mac's houseboat a lot!

That houseboat looks sooo cute! Maybe I should move
It really looks very similar to Mac's.

Yep, thats a houseboat alright!

Hey how do you know its the one I found in gEarth? you use co-ordinates or something?

Not quite, I assumed... The photo was said to have been taken at Coal Harbour and from the two houseboats docked next door, it HAS to be it. Those are some pretty unique looking houseboats.

I guess that I should have worded it differently. Sorry, if I'm wrong.

I just went back and compared the gEarth pic with your photo... It does look like the same houseboat.

If I remember correctly it was also the only houseboat of that design in the marina so, I'd say with a fair amount of certainty that you did find the same one.

Nice work.