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Results 1 to 12 of 12
  1. #1

    Cool 1973 Honda B75 converted to propane power

    Hello all honda lover's

    I recently acquired a honda b75 ser # b75-1003075 and it had some top end carb issues. The main jet needs an 0 ring and fuel shut off needs a new rubber stopper.

    So I decided to remove the dirty gas carb (gasoline is a dirty fuel with all the carbon, and gas souring in 60 days due to ethanol, carb is very clean), and build a very simple propane carb for the motor. Just some copper tube and a good regulator.

    So if have carb trouble with a 4 stroke honda this maybe an option for you

    Have the idle now down from spec 1200 to 575 and purrs like a kitten, a top end is same at 5000 rpm

    Use a $13.00 20 lb bottle of propane in 50 hours at trolling speed

    And more worries about storing the fuel, and my brother can not steel the gas for his car

    just a thought for anyone with an old 4 stroke that the parts are obsolete
    Last edited by Honda_B75; 05-25-2012 at 12:46 PM.

  2. #2

    Default Re: 1973 Honda B75 converted to propane power

    Great post! Just saw my first commercially produced propane outboard the other day (5 Hp) ---nice to know you can do your own conversion.

  3. #3
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
    Posts
    1,739

    Default Re: 1973 Honda B75 converted to propane power

    I just want to know where you're buying you're fuel!! I'd love me some $0.60 a gallon steaks for me barbi!

    Gday mate!

  4. #4
    Join Date
    Sep 2008
    Location
    Hague, Virginia, USA
    Posts
    2,283

    Default Re: 1973 Honda B75 converted to propane power

    Honda_B75 - It would be neat if you posted more detail on exactly how you did that and what parts you used.
    CHawk 25 DLX

  5. #5

    Default Re: 1973 Honda B75 converted to propane power

    Quote Originally Posted by chawk_man View Post
    Honda_B75 - It would be neat if you posted more detail on exactly how you did that and what parts you used.

    How i converted to propane

    For most 4 strokes simple putting propane into the air mix will make it run, however i had carb issues

    So i completely removed all fuel systems (carb and fuel pump)

    I then put a propane torch into the intake manifold to see what would happen, and to my delight the motor started right up at a low chug

    Then i started looking for stuff to Canibalize , and found the turkey deep fryer to have a nice variable pressure regulator on it, so stole that

    I then found an water hook up kit for an ice maker (the plastic tubing and a saddle back valve) unscrewed saddle and to my luck was the same npt thread as the regulator

    So i now i have the 20 lb propane tank hooked up with the 1/4 plastic tubing at the end (tank, variable regulator, the saddle back needle valve - the saddle removed, compression fitting to plastic 1/4 inch hose

    "Carb making" Made a template of intake out of 1/2 inch uhmw (plasic cutting board) x 2 , drilled a 1/2 inch hole put a 3 inch 1/2 inch piece of copper between them
    and made a carb.

    bolted it on to motor with oem bolt and then applied propane and engine ran,

    Ok well this is a start i will need to find out how to link pictures for this to make sense, but is a start
    Last edited by Honda_B75; 05-31-2012 at 11:55 AM.

  6. #6

    Default Re: 1973 Honda B75 converted to propane power

    Got some pictures

    Click image for larger version. 

Name:	Honda B-75 Side Carb.jpg 
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ID:	4627Click image for larger version. 

Name:	Honda B-75 Carb  Overhead.jpg 
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ID:	4628Click image for larger version. 

Name:	Propane tank setup.jpg 
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ID:	4629

  7. #7

    Default Re: 1973 Honda B75 converted to propane power

    Click image for larger version. 

Name:	Honda B-75  Boat view.jpg 
Views:	140 
Size:	79.0 KB 
ID:	4630o on boat, the deck screws keep it from sliding down shaft, (just simply screwed in to plastic then threw copper pipe) high heat silicone to seal up.

    NOTE: never put propane inside boat, propane if leaks or vents will pool at lowest point danger danger explosive whenever

    will try to post a video of motor start and running
    Last edited by Honda_B75; 05-31-2012 at 01:01 PM.

  8. #8

    Default Re: 1973 Honda B75 converted to propane power

    Hello, can you help me find the parts that I need from Ace Hardware's website and/or Home Depot so that I can buy what I need from the stores for this conversion? Here's what I would need to find:

    1. water hook up kit for an ice maker (the plastic tubing and a saddle back valve)
    2. variable pressure regulator

    The rest of the supplies I can figure out. My challenge has been not being able to locate a main jet for my newly rebuilt 1975 B75 Honda 7.5 Outboard. She's ready to go, otherwise. So, I'm guessing the propane conversion is the way to go.

  9. #9
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
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    1,739

    Default Re: 1973 Honda B75 converted to propane power

    Welcome to the forum.
    It is my opinion that the system described above would not be very economical to operate in that there is no regulation of the fuel for ON DEMAND delivery. You would simply be "fogging" the fuel in on a "guesstimation" schedule and the possibility for waste is evident. Will it work? Yes, absolutely. Is it efficient or cost effective? I doubt it. There is also a bit of safety to consider with a project like this and that may or may not concern you. Do you boat with your family?

    If it were me, I would continue to solve the jet problem. Have you tried the local "speed" or hot rod shops in your area? There are usually many jet options in those types of stores and you might find something you could use.
    If you have the old jet but it is worn and oversize, you could simply braze in the hole and re-drill. If undersize for your altitude, drill baby, drill!

    You may find that propane (LPG) will present you with some unique problems, especially if you live in a colder climate. Cold start enrichment can be problematic in cool weather with LPG and, sometimes, preheating the engine (ironically by running it on gasoline) could be necessary to get the old girl going.

    Valve icing can be another issue as the drop in pressure as the fuel leaves the tank can cause a "refrigeration" effect and in places of high humidity, icing will easily occur.

    I've worked on many engineered commercial LPG systems and have experienced all of the above. There is much info out there on the net about LPG conversion from gasoline and I suggest you do some reading before you jump in with both boots. Impco is a company that probably makes something that you could utilize to achieve an efficient, economical to operate and SAFE conversion. The initial cost is high, I realize, but the fuel savings and performance, in the long run, should offset that outlay.

    Whichever way you go, may the seas be calm and the winds be fair.
    Good luck.

  10. #10
    Join Date
    Sep 2008
    Location
    Hague, Virginia, USA
    Posts
    2,283

    Default Re: 1973 Honda B75 converted to propane power

    Jimmy - you ought to write a book - something on the order of "Outboard Repair - Beyond the Manuals." No kidding.
    CHawk 25 DLX

  11. #11
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
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    Default Re: 1973 Honda B75 converted to propane power

    Are you trying to get me in trouble chawk? I Hope your trip went well and was productive.

  12. #12
    Join Date
    Sep 2008
    Location
    Hague, Virginia, USA
    Posts
    2,283

    Default Re: 1973 Honda B75 converted to propane power

    Well - thought you might need another "project!" Trip went fine. Thanks for asking.
    CHawk 25 DLX

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