Fast, Small, Boat Designed Around Mercuiser 140

Discussion in 'Boat Design' started by jlclar09, Jul 2, 2013.

  1. PAR
    Joined: Nov 2003
    Posts: 19,126
    Likes: 498, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The racer I did last year is 30' x 6' and very successful currently.
     
  2. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,386
    Likes: 1,042, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Designing and building a new boat from scratch to utilise an old engine that must be in it's twilight years doesn't strike me as the best plan, I'd be more inclined to repair the rotten bits in the existing boat it sits in.
     
  3. PAR
    Joined: Nov 2003
    Posts: 19,126
    Likes: 498, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Agreed, it's usually better just to find another boat and transfer the pieces, if the donor craft is too bad off. This said, building a pocket rocket is fun, though most don't use an outdrive, it's certainly an option, if you have one dangling out of your back pocket, looking for a home. I had an Alpha and a 160 HP GM I-4 here I debated just this for, until I sold them as a package.
     
  4. powerabout
    Joined: Nov 2007
    Posts: 2,944
    Likes: 67, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    thast a compromise with what happens when your stopped....
    race boat ok, fishing boat its not ok
     
  5. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,386
    Likes: 1,042, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    What does a 140 MC sterndrive weigh, complete ? I'm thinking twice the weight of an outboard of the same output from the era. That could be a problem sitting right aft in a skinny boat.
     
  6. PAR
    Joined: Nov 2003
    Posts: 19,126
    Likes: 498, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    A 140 HP 4 stroke is in the 380 - 400 pounds range. An Alpha drive is 75 to 85, depending on which generation, so yes the 181 CID GM I-4 with and outdrive will be a little heavier than an outboard, but not by as much as you'd think and that weight isn't hanging on the transom either, but a few feet inboard of it.
     
  7. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,386
    Likes: 1,042, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Mercury site says (288kg) 635 lbs with Alpha drive ?
     
  8. PAR
    Joined: Nov 2003
    Posts: 19,126
    Likes: 498, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I've seen various figures for the 3.0 GM I-4 setup with and Alpha.

    http://www.mercurymarine.com/engines/mercruiser/sterndrives/3.0/

    This spec sheets says 1,040 lbs. (455 kg) which is more then the big block and 72C, struts, 17" wheel and shaft on my race boat!

    I have an older Alpha here and I can easily lift it and drag it around the yard. Once you count everything typically on this arrangement, it can by in the mid 600 pounds range. A dry exhaust, with an exchanger, instead of a big 'ol cast iron manifold and it's related stuff, will get you into the 530+ range.

    We're in agreement that this is heavier per HP than an outboard, but weight distribution is better and for some, so is serviceability. This engine does hot rod well too. The exhaust ports are easily "freed up", some roller rockers will offer another 10 - 15 ponies, a good intake and carb another 10 - 20, with a heavily wrapped header and you're cooking with gas, instead of coal. I'm not sure how far you can punch the bores, but 30 - 40 wouldn't be unreasonable offering a few more cubes, which is free power. They're running a 9:1 compression ratio with this engine, so it'll eat cheap fuel, but if it was jacked to 10:1 or 10.5:1, she'd stomp a lot harder. It runs a lot of small block Chevy parts, including pistons, so there's some more options.

    My point is, most anything can be made to run better and not necessarily decrease reliability. The power to weight ratio can be increased, to near outboard levels and with the weight distribution issue, a thing to think about. The next time I find a healthy Mercruiser/Alpha setup, I'll strongly consider this again. They're plentiful down here and the next $500 boat I find, with a good one on it, might get dragged to the landfill, less the engine/drive package. I'm thinking a well shaped molded or stripped hull, lot of shape, but not much weight, about 20', little beam, a dinky windshield and a couple of seats. Yeah, it'll be a crap fishing boat, but it'll be a fine bar hopper. Maybe I'll put a compressor on the little engine and have a real fridge, instead of an ice box.
     
  9. DCockey
    Joined: Oct 2009
    Posts: 5,229
    Likes: 634, Points: 113, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

  10. powerabout
    Joined: Nov 2007
    Posts: 2,944
    Likes: 67, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    the only thing I wouldnt do with a 140 is overbore too much as the bores are very thin
    but yes its does hot rod well as PAR says
    the engine was used in several dirt track classes in OZ and the US
     
  11. PAR
    Joined: Nov 2003
    Posts: 19,126
    Likes: 498, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Yep parts are available or you can weld up you own stuff. I've made a header for these (land based) and I'll bet I could do a fine job with an intake too. Toss on a 390 CFM 4 barrel carb, maybe a couple of Webers and a 230 degree cam and watch her go.
     
  12. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 148, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    That is correct.
    The engine is approx. 200kg. I use one as deadweight for a mooring, it performs better that way than it ever in my boat.
    Everything else Mercury says about this engine is questionable though. The torque is a well kept secret, the power is given in horse powers, but these are a special breed. To me pony powers seems more appropriate.
     
  13. PAR
    Joined: Nov 2003
    Posts: 19,126
    Likes: 498, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I've worked on a lot of these motors over the years and they all respond well to improvements or regular maintenance. Neglect one and it's not the engine's fault. The newer ones are EFI and electronic ignition, so very reliable. The best thing you can do to the older ones, is put a electronic ignition up grade on it.
     
  14. powerabout
    Joined: Nov 2007
    Posts: 2,944
    Likes: 67, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member


  15. jlclar09
    Joined: Jul 2013
    Posts: 6
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Cincinnati

    jlclar09 Junior Member

    Sorry I havn't responded in a while, been buisy fixing yard after all the rain... So it sounds like I can get some good power out of this heavy turd of an engine with some work. My main vision was something like the bond Q-Boat from The World Is Not Enough. They said that it used a 5.7L V8 with jet drive. It looked like a short boat. I was thinking of using this as a base template... thoughts?
     
Loading...
Similar Threads
  1. Schnick
    Replies:
    4
    Views:
    1,889
  2. Arctic sailor
    Replies:
    1
    Views:
    2,045
  3. Squidly-Diddly
    Replies:
    25
    Views:
    2,424
  4. Bullshipper
    Replies:
    7
    Views:
    1,385
  5. Prinex
    Replies:
    19
    Views:
    1,934
  6. socalspearit
    Replies:
    221
    Views:
    21,503
  7. mitchgrunes
    Replies:
    5
    Views:
    2,268
  8. tonipu
    Replies:
    34
    Views:
    3,108
  9. Squidly-Diddly
    Replies:
    105
    Views:
    16,668
  10. jon haig
    Replies:
    23
    Views:
    6,289
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.