Page 1 of 2 12 LastLast
Results 1 to 35 of 56

Thread: Smallest boat with an inboard?

  1. #1
    Join Date
    Oct 2004
    Location
    Boston
    Posts
    661

    Default Smallest boat with an inboard?

    So what is the smallest (shortest length) boat with an inboard you have seen or read about? Any limitations to boat length besides shaft angle and space?

  2. #2
    Join Date
    Apr 1999
    Location
    West Boothbay Harbor, Maine
    Posts
    24,274

    Default

    The 'push boats' for the Maine Windjammer schooners are about 14 feet long with honking great engines, and LIBERTY, a Hodgdon built commuter yacht has an inboard dinghy maybe 12' long. Beautiful lapstrake, with a beamy Whitehallish shape. The shaft (tiny prop!) passes almost level through the deadwood and the outboard rudder is cut out to clear the wheel. It's so lightweight that I think the crankshaft-to-propshaft connection may be bicycle chain and gears to get the shaft low and level... but I'd have to check on that.

    I imagine that electric motors could make a very small inboard possible in a similar way.
    “Eventually, all things merge into one, and a river runs through it. The river was cut by the world's great flood and runs over rocks from the basement of time. On some of those rocks are timeless raindrops. Under the rocks are the words, and some of the words are theirs."

  3. #3
    Join Date
    Dec 2000
    Location
    Chesapeake Beach, Md 20732 U.S.A.
    Posts
    26,724

    Default

    Jay Benfords 8 1/2 foot steam dink....
    Wakan Tanka Kici Un
    ..a bad day sailing is a heckuva lot better than the best day at work.....
    Fighting Illegal immigration since 1492....
    Live your life so that whenever you lose, you're ahead."
    "If you live life right, death is a joke as far as fear is concerned."

  4. #4
    Join Date
    Jan 2005
    Location
    Deepest Darkest Wales
    Posts
    22,771

    Default

    These are short
    I'd much rather lay in my bunk all freakin day lookin at Youtube videos .

  5. #5
    Join Date
    Oct 1999
    Location
    St. Paul, MN, USA
    Posts
    57,118

    Default

    For traditional designs, Weston Farmer's aptly named 10' "Irreducible". Here's a link to the original article in the Rudder: http://www.duckworksbbs.com/plans/wf...ible/index.htm


    "For a successful technology, reality must take precedence over public relations,
    for nature cannot be fooled."

    Richard Feynman

  6. #6
    Join Date
    Oct 2004
    Location
    Boston
    Posts
    661

    Default

    That is exactly what I had in mind. It sure is a cute one. What I wouldn't give to have a 1.5-3 HP one-lunger make and break...

  7. #7
    Join Date
    Aug 2005
    Location
    SF Bay Area- Richmond
    Posts
    16,412

    Default

    You may need to define the question further to get what you are looking for -- are you asking in an historical sense, or regarding modern motors and designs?

    From the various discussions on the forum, it seems that motors have gotten larger and produce higher rpm's than 100 years ago, thus limiting their use as inboards in small boats. They seem to be being replaced with electric motors nowadaze -- does that count?

    ;0 )
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  8. #8
    Join Date
    Oct 2004
    Location
    Boston
    Posts
    661

    Default

    I'm really leaning towards traditional applications...and I cringed a little at that picture of the jetski. With so many small boats, it's very hard finding a good small boat inboard engine of the traditional kind, something along the lines of a raw water cooled one cylinder gas engine (or even air cooled). Lawmower engines just dont have the stroke and the RPMs are way too high...

  9. #9
    Join Date
    Mar 2005
    Location
    Toronto, Canada
    Posts
    2,919

    Default

    The introduction to our host's Fifty Wooden Boats has the lines, construction and offsets for the Irreducible. It's written by Weston Farmer.

    Norm

  10. #10
    Join Date
    Aug 2005
    Location
    SF Bay Area- Richmond
    Posts
    16,412

    Default

    There has been some interesting discussions on how to use belts to reduce the rpm on inboard engines on the Rescue Minor threads here -- well worth checking out! Going to the agricultural machineshops sounds like a great idea for belt and pully setups that would really work.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  11. #11
    Join Date
    Dec 2000
    Location
    Chesapeake Beach, Md 20732 U.S.A.
    Posts
    26,724

    Default

    BIL modified a weedwhacker motor and fitted it inside an 8 foot dink that I built back in '69......he used it as a fishing boat for years...
    Wakan Tanka Kici Un
    ..a bad day sailing is a heckuva lot better than the best day at work.....
    Fighting Illegal immigration since 1492....
    Live your life so that whenever you lose, you're ahead."
    "If you live life right, death is a joke as far as fear is concerned."

  12. #12
    Join Date
    Sep 2004
    Location
    Ohio
    Posts
    3,514

    Default

    I built on of these about 1964. Eight feet long. Had two inboard chainsaw engines.


  13. #13
    Join Date
    Oct 2004
    Location
    Boston
    Posts
    661

    Default

    So there is an easy way to get low rpms, high torque, and steady running speeds out of a short stroke 2 stroke engine without re-maching crankshafts etc? How did you tune the rpm's down and keep the torque high enough to turn a wheel? I love Irreducible...it's finding an engine that suits the boat that's hard to find. Maybe a small 2-3HP lawnmower engine with a flywheel to steady, mounted in a housing with a fat duct to scoop up air...something quick and dirty...
    Last edited by maa. melee; 07-26-2006 at 03:26 PM.

  14. #14
    Join Date
    Oct 2001
    Location
    Flattop Islands
    Posts
    2,338

    Default

    Strikes me that far more satisfactory power for Irreduible would be an electric trolling motor embedded in the rudder.

    Course...then you miss all the noise, smoke, stink, and expense of an infernal combustion plant.

    Tad

  15. #15
    Join Date
    Jul 2002
    Location
    Port Orchard, Washington, USA
    Posts
    1,744

    Talking Very Small Inboard Boat

    Quote Originally Posted by maa. melee
    So what is the smallest (shortest length) boat with an inboard you have seen or read about? Any limitations to boat length besides shaft angle and space?
    About 6"....



    http://www.sciencetoymaker.org/boat/index.htm

  16. #16
    Join Date
    Oct 1999
    Location
    St. Paul, MN, USA
    Posts
    57,118

    Default

    Some further inspiration - here's another Weston Farmer design for a sweet little 16' double-ended launch, bizarrely named "Assassin", with a similar motor. Look here: http://www.duckworksmagazine.com/sto...ssin/index.htm
    One could certainly use a trolling motor in the rudder (or instead of the rudder for maximum simplicity), or alternately a DC motor in place of the inboard gas engine. The latter would require a certain amount of thinking to work out the batteries and speed control, but it would work fine and be almost silent. Electric Propulsion For Boats by Charles Mathys, or Electric Boats by Doug Little (now out of print but available used) cover the subject. OTOH, the experience of electric power is very different from running a small slow-turning gas engine - better or worse is your call.

    Last edited by Keith Wilson; 07-26-2006 at 04:54 PM.
    "For a successful technology, reality must take precedence over public relations,
    for nature cannot be fooled."

    Richard Feynman

  17. #17
    Join Date
    Oct 2001
    Location
    Flattop Islands
    Posts
    2,338

    Default

    This one is 13'6" overall, with a beam of 5'7". Her power is a 7HP BMW single cylinder diesel turning a 12" by 8" three blade prop.





    That would be the designer at the helm, I'm not really unhappy just trying not to scratch the varnish.

    Tad

  18. #18
    Join Date
    Dec 2000
    Location
    Chesapeake Beach, Md 20732 U.S.A.
    Posts
    26,724

    Default

    dogonnit Tad....build a glass box around that one....
    Wakan Tanka Kici Un
    ..a bad day sailing is a heckuva lot better than the best day at work.....
    Fighting Illegal immigration since 1492....
    Live your life so that whenever you lose, you're ahead."
    "If you live life right, death is a joke as far as fear is concerned."

  19. #19
    Join Date
    Oct 2004
    Location
    Boston
    Posts
    661

    Default

    Wow what a boat...that pic should be on the label of a can of varnish.
    As for electric boats...them are horses of a different color...
    I prefer the sound, smoke, grease, and rugged-stouborness of a small gas engine.

  20. #20
    Join Date
    Oct 2003
    Location
    Valley of the Sun
    Posts
    105,555

    Default

    So what is the smallest (shortest length) boat with an inboard you have seen or read about?
    I once saw a yawl boat for one of the oystering skipjacks, similar to the boat pictured below. The yawl boat was less than ten feet long and had Buick 455 cu in inboard in it.

    Simpler is better, except when complicated looks really cool.

  21. #21
    Join Date
    Dec 2003
    Location
    on-the-cuyahoga
    Posts
    13,063

    Default

    Clark Craft offers plans for Heckle and Jeckle. About 8' long. One is powered by a 250cc motorcycle engine that sits amidship between the pilots knees. Because the motor has an integral gearbox you can lock it in whatever gear gives you the proper propeller RPM range.
    Last edited by Cuyahoga Chuck; 07-27-2006 at 10:48 AM.

  22. #22
    Join Date
    Aug 2004
    Location
    Western Michigan
    Posts
    705

    Default

    maa. melee, e-mail me. I can direct you to such an engine if you are interested.
    If you don't know where you're going, you might not end up there.-Yogi Berra

  23. #23
    Join Date
    Apr 2002
    Location
    Madison, Ohio
    Posts
    103

    Default

    Hey Cuyahoga,
    I have been building Jeckyl......for several years. One of these days I am going to finish it. I have been too busy working on our house project and putting my workshop together. I need to get ahold of that Glen-L book about inboard installations. The hull is about done except for finishing but I have kind of let the motor and hardware installation stall my progress.

  24. #24
    Join Date
    Dec 2003
    Location
    on-the-cuyahoga
    Posts
    13,063

    Default

    Win,
    I remember.
    You were looking to use a snowmobile engine which is about 3 times bigger than what they recommended. And because those motors have no transmissions I suggested there was no easy way to get the prop RPM's down to workable levels.
    That's the chink in any small motor installed in a boat. If you try to run the prop at motor speed the boat is rather uncontrollable in tight places and the prop may be going too fast to drive the boat well in the open.
    I don't think Glen-L is going to help you. An inboard installation in an 8' hull doesn't allow much room for interpretation. Whoever designed that set-up had to have figured out how to make the bike engine work in a boat. If he didn't proove it was practical the design wouldn't be saleable.
    Jeckyl is so unusual that everything you need to know should be on your plans. If it isn't you've got a problem.
    Last edited by Cuyahoga Chuck; 07-27-2006 at 06:47 PM.

  25. #25
    Join Date
    Aug 2009
    Location
    St. Louis
    Posts
    3

    Default Re: Smallest boat with an inboard?

    This is a picture of my 12 ft 4in Tewksbury, with a 1968 Palmer PW27 8hp inboard. I use it all the time. It's the smallest inboard I know of.
    http://www.oldmarineengine.com/discu...54/134943.html




    Quote Originally Posted by Cuyahoga Chuck View Post
    Win,
    I remember.
    You were looking to use a snowmobile engine which is about 3 times bigger than what they recommended. And because those motors have no transmissions I suggested there was no easy way to get the prop RPM's down to workable levels.
    That's the chink in any small motor installed in a boat. If you try to run the prop at motor speed the boat is rather uncontrollable in tight places and the prop may be going too fast to drive the boat well in the open.
    I don't think Glen-L is going to help you. An inboard installation in an 8' hull doesn't allow much room for interpretation. Whoever designed that set-up had to have figured out how to make the bike engine work in a boat. If he didn't proove it was practical the design wouldn't be saleable.
    Jeckyl is so unusual that everything you need to know should be on your plans. If it isn't you've got a problem.

  26. #26
    Join Date
    Aug 2004
    Location
    Victoria BC, Canada
    Posts
    565

    Default Re: Smallest boat with an inboard?

    Quote Originally Posted by maa. melee View Post
    So what is the smallest (shortest length) boat with an inboard you have seen or read about? Any limitations to boat length besides shaft angle and space?
    Maybe not quite the shortest, but definitely the coolest, would be Alpha, the 12 foot clinker built dinghy with a steam engine. See http://www.northweststeamsociety.org for more.

    Jamie

  27. #27
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    51,389

    Default Re: Smallest boat with an inboard?

    I have seen small, with a Stuart Turner inboard, maybe a 10' clinker stem motor boat.
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  28. #28
    Join Date
    Apr 2005
    Location
    Hills of Vermont, USA
    Posts
    36,628

    Default Re: Smallest boat with an inboard?

    I used to have a 12' plywood lapstrake launch with an 8HP Yanmar in it. It now lives the next peninsula down from the original poster. Really fun boat for tooling around the Maine coast.

  29. #29
    Join Date
    Sep 2010
    Location
    UK
    Posts
    1,127

    Default Re: Smallest boat with an inboard?

    I always liked the Dutch opduwertje - used as push boats for sailing barges, usually with a chunky diesel or hot bulb engine. Steel, of course.



  30. #30
    Join Date
    Apr 2005
    Location
    Hills of Vermont, USA
    Posts
    36,628

    Default Re: Smallest boat with an inboard?

    Nice clean wake from that.

    Not so much..... Pushing her beyond hull speed?

  31. #31
    Join Date
    Sep 2010
    Location
    UK
    Posts
    1,127

    Default Re: Smallest boat with an inboard?

    Quote Originally Posted by Garret View Post
    Nice clean wake from that.

    Not so much..... Pushing her beyond hull speed?
    I think that is the inevitable consequence of a short, heavy boat with loads of power, a huge prop and no hope in hell of planing! Still, must have moved those barges around pretty well.

  32. #32
    Join Date
    Mar 2009
    Posts
    1,791

    Default Re: Smallest boat with an inboard?

    Hydraulic drive may make it feasible to make a small high speed engine turn a big prop slowly. It also means that prop angle is not the same as engine angle (level is better for oil pickup etc.) and the engine can be placed just about anywhere it will fit in the boat. Reverse is also very easy to arrange. I am not sure about cost, but I bet a system sourced from low-end industrial supplier (Princess Auto, e.g.) would be pretty competitive with any kind of marine gearbox.

    One drawback is efficiency. 80% is about maximum efficiency from end to end on the hydraulic system. However, the higher efficiency of a large, slow prop may make up for this to some extent. It also needs a reservoir, which will take up room and add weight. Also, the low-end industrial stuff may not last well in a marine environment.

    It might be fun to try, though.

  33. #33
    Join Date
    Jan 2012
    Location
    Olympia,WA
    Posts
    130

    Default Re: Smallest boat with an inboard?

    I think one of the designer on here built a little tug with a inboart not too long ago. can't remember. maybe tad roberts I think.

    Outlaw

  34. #34
    Join Date
    Oct 2001
    Location
    Flattop Islands
    Posts
    2,338

    Default Re: Smallest boat with an inboard?

    Quote Originally Posted by robm View Post
    the engine can be placed just about anywhere it will fit in the boat.
    Unless you come up with an engine that weighs nothing, the only place to put the engine in a very small boat is right in the middle. Anything else is bad design. It is tempting to move the engine forward, to be countered by crew weight aft.....But the boat sits nose down when empty which looks like a mistake....
    ___________________________________
    Tad
    cogge ketch Blackfish
    cat ketch Ratty
    http://www.tadroberts.ca
    http://blog.tadroberts.ca/
    http://www.passagemakerlite.com

  35. #35
    Join Date
    Oct 2001
    Location
    Canberra
    Posts
    4,492

    Default Re: Smallest boat with an inboard?

    Quote Originally Posted by maa. melee View Post
    What I wouldn't give to have a 1.5-3 HP one-lunger make and break...
    That's what I had on my 12' clinker putt-putt Serenity -- a single-cylinder Blaxland (traditionally painted red, not blue) --


    It had a dog-clutch which allowed you to move it from neutral to forward. That was all. If you needed to go in reverse you stopped the engine altogether, then started it again by pulling the flywheel round backwards -- instant reverse....

    You removed the magneto altogether and took it ashore with you to stop the vessel being stolen.

    Mike
    Visit us to see how we help people complete classic boats authentically.

Similar Threads

  1. New boat builder looking for help...
    By wilsonj in forum Building / Repair
    Replies: 24
    Last Post: 10-23-2007, 05:11 PM
  2. quick and dirty pulling boat build
    By TomF in forum Designs / Plans
    Replies: 29
    Last Post: 06-19-2006, 12:07 PM
  3. Deck Caulk (grab that stick, this horse is only kinda dead) Repost
    By Jim Hillman in forum Building / Repair
    Replies: 0
    Last Post: 11-11-2005, 03:10 PM
  4. The future of timber boat construction
    By studentUK in forum Building / Repair
    Replies: 29
    Last Post: 04-17-2005, 07:56 PM
  5. Repost "Double planked runabout" (NIA)
    By Ross M in forum Building / Repair
    Replies: 0
    Last Post: 10-26-2002, 02:16 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •