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  1. #1
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    Oct 2004
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    Default Difference between 1 and 2 cylinder outboards

    I'm shopping for a new kicker for the sailboat. I want to reduce weight both to raise the ass end of the boat and to make it easier to remove, so I'm considering a 6hp to replace the current 8hp motor. While shopping, I noticed that Yamaha makes two different 6hp motors; one that's two cylinders and one that's just one cylinder. If both are 6hp, will the two cylinder model be able to produce more thrust than the single cylinder? Ordinarily, I'd incline toward the 2 cyl, but it's considerably heavier. Any thoughts on this?
    2001 220 Cuddy (Stalker)
    5.7 (350) PCM FWC

  2. #2
    Join Date
    Oct 2004
    Location
    Annapolis, MD
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    Default

    For what it's worth, here are some specs:

    Type: Outboard Motor
    Year: Current
    Model: F6 HP
    Model Number: F6AMSH
    Series: Four Stroke Portable
    HP: 6
    Engine Type: 2 Cylinder
    Displacement: 8.5 ci
    Compression Ratio: 8.9
    RPM Range: 4500-5500
    Fuel Delivery System: Carbureted
    Fuel Type: Unleaded gasoline (minimum pump octane 87)
    Exhaust: Thru prop
    Ignition System: CDI
    CARB Rating: 3-Star
    Alternator Output at WOT: 6A
    Starting System: Manual
    Lubrication: Wet Sump
    Gear Ratio: 13
    Control Type: Tiller Handle
    Trolling Throttle Adjustment: N/A
    Cooling: Water, Thermostatic Control
    Weight: 83 lb
    Gear Shift: F-N-R
    Command Link System: No
    Enhanced Ultimate Corrosion Protection System UCP: Standard Feature
    Power Trim and Tilt: No
    Power Tilt: No
    Shaft Length: 15 inch
    Gearcase Rotation: Left Hand
    Stop Switch Lanyard: Yes
    Ultimate Corrosion Protection System: Yes
    3 Year Limited Warranty: Yes
    Thermostatic Cooling System: Yes
    Aluminum Propeller: Standard
    Tiller Handle Steering: Standard
    Engine Sensing Warning System: Standard
    High Output Alternator: Optional
    Dual Thrust Prop: Optional
    Shallow Water Drive: Standard





    Engine Type : 1 cyl.
    Displacement : 8.5 ci (139 cc)
    Compression Ratio : 8.9:1
    RPM Range : 4500-5500
    Fuel/Induction System : OHV
    Ignition System : CDI
    Alternator Output @ W.O.T. : 6A **
    Starting System : Manual
    Lubrication : Wet Sump
    Gear Ratio : 13:27 (2.08)
    Shaft Length : 15 in., 20 in.
    Weight : 60 lb (27 kg)
    CARB Rating : 3-Star
    Warranty : 3 Year Limited Pleasure Boat - 1 Year Limited Commercial
    Mileage: 0
    2001 220 Cuddy (Stalker)
    5.7 (350) PCM FWC

  3. #3
    Join Date
    Sep 2006
    Location
    Corpus Christi Texas
    Posts
    4,175

    Default

    quickstep192, what type of sail boat, and do you need an alternator that comes on both versions?

    On the outboards, some are tuned down and weigh the same; so I would select the one that is tuned up.

    I have a very small Honda 20 inch shaft 2 hp 4 stoke 1 cylinder I like, and it weighs 39 pounds
    1996 200 WA
    5.7 Indmar TBI
    275 HP FWC full system
    Hurth

    Preserve, protect and defend the Constitution of the United States of America so help me God

  4. #4
    Join Date
    Apr 2003
    Location
    Eastern Shore, Va.
    Posts
    2,314

    Default

    Maybe the thinking is along the lines of the reason my 3-cylinder 40hp Yamaha has THREE CARBS: If one craps out, maybe the other two will still work.

    It never made sense to me if the question was simplicity or rebuilding carbs (why 3 instead of ONE?) but for safety's sake, it's redundancy I guess.

    If you just had ONE carb (or ONE cylinder or spark plug or coil or coil wire or magneto pickup) ...

    ... versus TWO of each ...

    ... your chances of a disabling breakdown would be DOUBLED!

    Having TWO instead of ONE cuts your risk of being completely disabled in HALF. You might limp, but at least you'd get home without sneakers and water wings.

    If you plan to regularly use and/or maintain the motor, I would opt for two cylinders over one for this reason.

    In a car, I would say just the opposite. But it's hard to walk home from broke boats.

  5. #5
    Join Date
    Dec 2008
    Location
    Elberta, AL
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    Default

    Quote Originally Posted by Capt Crunch View Post
    Maybe the thinking is along the lines of the reason my 3-cylinder 40hp Yamaha has THREE CARBS: If one craps out, maybe the other two will still work.

    It never made sense to me if the question was simplicity or rebuilding carbs (why 3 instead of ONE?) but for safety's sake, it's redundancy I guess.

    If you just had ONE carb (or ONE cylinder or spark plug or coil or coil wire or magneto pickup) ...

    ... versus TWO of each ...

    ... your chances of a disabling breakdown would be DOUBLED!

    Having TWO instead of ONE cuts your risk of being completely disabled in HALF. You might limp, but at least you'd get home without sneakers and water wings.

    If you plan to regularly use and/or maintain the motor, I would opt for two cylinders over one for this reason.

    In a car, I would say just the opposite. But it's hard to walk home from broke boats.
    The way a 2 stroke works is right behind the carbs are reed valves, if you ever take a 2 stroke apart you will notice the crank had channels cut into it, the fuel has to have a realitivly stright shot to the cylinder. The vacume of the piston pulls the fuel from the carb onto that channel in the crank, then the applied forces sling that fuel into the cylinders to atomize. That would not be possible with only 1 carb. best I can tell. As far as 1 vs. 2 cylinders it is probably marginal as far as the difference. The bigger you go on the motor the additional cylinders provide a longer lasting motor. As in you example of a 40 HP Yamaha, they make a 2 cylinder version and a 3 cylinder version. They are heavier but have to work less to provide the same HP. If you notice the 1 cylinder in these small motors have a slightly higher gear ratio. I would think you would get a pinch more torque out of the 2 cylinder since you have more rotating mass.
    IF IT CAN'T BE FIXED WITH A HAMMER, ITS AN ELECTRICAL PROBLEM
    "The Best Bilge Pump Is A Scared Man With A Bucket"
    83 20' Cuddy Shammy 350 Chevy - SOLD
    21' Carolina Skiff 140 Tohatsu Jet Drive - Fish Killin, Shallow Running Machine that would make any Hell's Bay Jealous
    1999 26' Open 350 Carb - "SHAMWOW!" - FOR SALE
    "I would rather have a gun in my hand than a cop on the phone" - Author Unknown

  6. #6
    Join Date
    Sep 2006
    Location
    Corpus Christi Texas
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    Default

    Quote Originally Posted by Capt Crunch View Post
    Maybe the thinking is along the lines of the reason my 3-cylinder 40hp Yamaha has THREE CARBS: If one craps out, maybe the other two will still work ...
    Had a 1979 75hp johnson stinger 2 stroke with 3 cylinders and 3 carbs. That motor ran for 20 years on a 16 foot aluminum starcraft bowrider and was gifted to a cousin for his pontoon boat after the boat wore out.

    The only issue with that motor that occured, was a limp-home one time and it needed new rings on one of the cylinders; the carbs alway worked fine
    1996 200 WA
    5.7 Indmar TBI
    275 HP FWC full system
    Hurth

    Preserve, protect and defend the Constitution of the United States of America so help me God

  7. #7
    Join Date
    Mar 2010
    Location
    mobile alabama
    Posts
    1,204

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    Difference between 1 and 2 cylinder outboards ...................1 cylinder? http://www.youtube.com/watch?v=oeMwHZrUbVA

    I couldn't resist \ but waited until a few serious and informative posts occured first!
    Bill

    Government's first duty is to protect the people, not run their lives. Ronald Reagan

    1998 246 Adventurer (Walk Around Cuddy) with a RWC TBI THREEFITY

  8. #8
    Join Date
    Apr 2003
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    Eastern Shore, Va.
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    Quote Originally Posted by Fully_Loaded View Post
    The way a 2 stroke works is right behind the carbs are reed valves, if you ever take a 2 stroke apart you will notice the crank had channels cut into it, the fuel has to have a realitivly stright shot to the cylinder. The vacume of the piston pulls the fuel from the carb onto that channel in the crank, then the applied forces sling that fuel into the cylinders to atomize. That would not be possible with only 1 carb. best I can tell.
    Hmmm...I had a 1973 Evinrude 40hp 2-cylinder that had only 1 carb...

  9. #9
    Join Date
    Dec 2008
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    Elberta, AL
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    With a 2 cylinder it may be possiable because you can place the carb between the 2 cylinders and the reed valves would split the fuel.
    IF IT CAN'T BE FIXED WITH A HAMMER, ITS AN ELECTRICAL PROBLEM
    "The Best Bilge Pump Is A Scared Man With A Bucket"
    83 20' Cuddy Shammy 350 Chevy - SOLD
    21' Carolina Skiff 140 Tohatsu Jet Drive - Fish Killin, Shallow Running Machine that would make any Hell's Bay Jealous
    1999 26' Open 350 Carb - "SHAMWOW!" - FOR SALE
    "I would rather have a gun in my hand than a cop on the phone" - Author Unknown

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