In article . com,
"Tim" wrote:

It's just a typical 18ft. runabout with inboard 4 cyl 140 mercruiser.
it ahs an inboard tank which I'm really not sure of the total capacity.
maybe 8-10 gal. I'd like to add an extra fuel tank or so, and was
wondering if it's actually legal to do so via coast guard approval.

i was thinking on getting a couple 6-10 gal tanks and putting them
under the rear seats, sealing the vents either tieing them together, or
using one as a reserve., Amd I was planning on filling them with the
main tank. In didn't know if this would present a problem so I thought
I'd ask here.

Legality has little to do with it, but playing with Momma Nature -- or
Poppa Darwin -- does.

Don't play around. Do it right. You really don't want to go boom.

Probably the easiest "fix" would be to carry a couple of "jerry" cans
that you can properly strap down. If you notice you're running out and
still want to keep going, stop, let things cool properly, fill up, then
get going again.

From running with friends with such boats on the Chesapeake, it seems
the tanks are properly sized. By the time they need to refuel, they're
ready to get out and stretch their legs.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/