The size of a small outboard...

Outboards sizes....

Ok so the websites say models come w 15 or 20" Leg length.
Where is this measured from?
Top of transom mount?

The reason is that I'm trying to get a rough idea of a few models full physical size, something they seem to neglect to include...

 

Outboard leg length is measured vertically from the antiventilation plate to the inside top of the transom bracket (where it touches the top edge of the transom). In reality something labelled 15" can be anywhere from 14 1/2 to 17 inches; a 20" could be from 19 to 22 inches. Most outboard makers these days aren't too proud of the fact that their motors are now bigger and heavier than those of 10 years ago (due to the extra technology now needed to stop them spewing gas and toxins into the lake) and so they are often reluctant to say just how bulky the motor is, unless it's unusually small.

 

Sometimes the net isn't the best place to get info, especially from mfg or dealers.

If these measurements are critical for your build, you might have to go to a dealer's showroom with a tape measure. That's what I have done! I have found some pretty big differences between the nominal listed specs and actual measurements. Weight varies, too, by the way.

Sometimes they look at me funny, but they haven't run me off yet!

 

Note also there can be up to a 40% difference in weight and size for motors of the same rated horsepower! (ie. a 50hp 3cyl carb 2-stroke vs. a 50hp 4cyl EFI 4-stroke).