YA young-boys series: japanese mini-submarine

As I recall, these books were a series - and I can't remember enough about it to be able to track it down. It was kinda like a Hardy Boys type series but it wasn't. (the hardy boys were too goody-goody for my liking and these weren't all specifically mysteries) Some of the themes bordered on sci-fi adventure as I recall.
What I do remember about it is that there was core of main characters, boys, who were kinda the semi-outcast, nerdy or at least the not-in-the-popular-crowd types anyway. And they were all into gizmos and gadgets and building stuff, etc. The best way I can describe what I remember of it was like a mix of Our Gang, the Goonies and the stories of Mark Twain. (I know, this probably describes most books geared at young boys) I also remember they had some kind of clubhouse or fort something.

About the only specific story that I remember from them in any detail was one where one of them somehow gets ahold of an old, WWII surplus 2-man japanese mini-submarine. He and some of the other guys fix the thing up and get it working again and start exploring one of the lakes in town. Among other things they do, they manage to trap a large airpocket somewhere under the water and build a second version of their clubhouse where they can go and none of the adults can bother them.

From time to time, I also remember other small blips and bloops that I think were from this book series but I can neither remember who wrote them, how many boys there were or what any of the other stories were about. I just remember always wanting to get more books from this series whenever I saw one.

Possibly the Tom Swift or Tom Corbett, Space Cadet series? They were sci-fi/science flavored boys' books along the Hardy Boys' type.

Both of those are a bit too big - Tom Swift is building a giant airplane in his father's factory in the first book, and Tom Corbett is, well, a space cadet - junior/trainee officer in the Space Patrol. The Rick Brant series by John Blaine is a little bit closer - though even there, the main character is the son of a literal rocket scientist, but he's more of a hobbyist than the semi-pro Tom Swift. I don't remember a clubhouse either. There is at least one with a submarine, but I don't think it's their toy or that they use it in a local pond.

Dunno. It sounds like a great series, though - if you find it, tell us!

Someone on facebook put me onto the correct series! The Mad Scientists' club by Bertrand R. Brinley! Woo hoo, one more scratched off the list. http://www.madscientistsclub.com/MSC/Books.html
Looking for them on Amazon I was also reminded of the old Encyclopedia Brown books.

Aha! I've seen those, but never read any. I'll have to check them out.

touchstone fairy - Mad Scientists Club - I loved these.