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  1. #1

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    1994 K&B .21 outboard in 2012 help

    In a blast from the past, I decided to take my 6 year old son RC boating.

    I have a Prather 31' Deep Vee outboard with a 1994 ish Black carb K&B outboard 3.5. Back then I was into airplanes and had great experience with plane engines. I built my Prather and being in Alaska I didn't have anyone around to help me with the boat. It was a tempermental engine and incredibly unreliable... so I shelved it.

    Fast forward to now, last week I gathered up my stuff, charged the batteries and took my son boating on Sunday.

    Here is my my problem:

    The motor is still tempermental. Ornery to start and keep running. There seems to be a lot of oil coming from the exhaust port and maybe crankcase of the back of the engine where it mounts on to the lower unit/drive. Is this an issue? Would this make the engine a poor runner? Do I need to remove the powerhead and seal those surfaces? I have checked the tank and fuel lines (and exhaust supply pressure line) for air tightness and they pass muster.

    The carb seems to need to be run more lean than the reocmmended starting of 3 1/2 turns open. As it is running it is too rich if there is fuel sputtering out from the carb right?

    Finally I got it running and let the boat loose and after it dying a few times (and then leaning it out) It ran, but then I broke the flex shaft. I live in Alaska, please direct me to a website where I can order (if at all) a new flex driveshaft for this motor and lubrication.

    Also this motor is bone stock. What kind of r/c glow plugs should I order (etc rc long/ short, idle bar or no idle bar). Does anyone have a suggestion on a prop. What about % nitro fuel?

    Thanks for the help! PS when the boat died, my yellow lab jumped in the water and was of no help retrieving it, yet when I turned my back she somehow bit into the hull and punctured it! Ha ha ha... guess I need some epoxy and little square of glass as well.

    Sobie2

  2. #2

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    RE: 1994 K&B .21 outboard in 2012 help

    I have one. Run a long reach glow plug use a cold plug for 25 percent nitro or more. And a hot or med plug for 20 percent and lower. If you use more than 30 nitro you might want to and add a head shim or two. Higher percent nitro likes less compression to make the engine last and not be so hard to tune.

    >>

    As of the fuel and oil coming out of the exhaust were it meets the lower unit it is normal there is no seal were they meet. But check to make sure your bolts that hold the engine to the lower unit are tight.

    >>

    Fuel spitting out of the carb doesn’t really mean its rich. Pay attention on how it sounds and how much it smokes you want it to have a little smoke coming out of the exhaust when at wide open throttle if you want the engine to live.

    >>

    Prop I am using a Prather 225 seems to b fine on 30 percent fuel. And 30 thou of head shims For 50 percent and have my needle adjustment around 3.5-4 for 25percent and 6-7 for 50 percent fuel.

    I would start with 25 percent fuel and try prop P 220 = 1.72 diameter X 2.6 pitch..

    A lot of boat engines don’t like to idle like a airplane engine, they usually have different carbs. A lot of the boat carbs don’t have a low speed fuel adjustment that is attached to the carb rotor or barrel whatever you want to call it.

    >>

    If it is hard to start try unhooking the fuel lines(supply and exh pressureto tank) and pull the glow plug then turn it over with the starter for about 10 seconds or until there is NO fuel or oil coming out of it.

    Put the plug back in and hook up the fuel lines Have the carb opening around 1/8 open from the closed position then turn it over until you see that the fuel is just getting to the carb inlet(watch the bubbles in the line)then stop and hook up the plug power and let the plug get hot around 5 seconds then try starting it. The engine should pop a little or fire up after two or three tries. You may have to play with how much or how little throttle you need some engines like to start at about 1/3 to half throttle mine seems to like it at a 1/8 open.

    here are a few web sites for stuff and the K&B web site also

    Hope this is of some help…

    >>

    Jeff

    >>

    Prop charts http://www.funrcboats.com/prop_chart1.htm

    Stuff good company fast and fair prices http://zippkits.com/~zippkits/index....8f6eaa38f7700b

    >>

    Fuel http://torconitro.com/

    >>

    K&B http://www.mecoa.com/kb/index.htm

    http://www.mecoa.com/acc/index.htm

    >>

    Prop charts http://www.funrcboats.com/prop_chart1.htm

    >>


  3. #3

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    RE: 1994 K&B .21 outboard in 2012 help

    I forgot about the flex shaft lube. you can use boat trailer axle grease it works fine and is at almost all auto parts store. the main thing is to take it out and clean it and relube after use especially after use in salt water.


  4. #4
    Ron Olson's Avatar
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    RE: 1994 K&B .21 outboard in 2012 help

    It's possible that the Power Take-Off bearings are shot, I've been there.
    IMPBA 17238 S
    269 Racing Team

  5. #5

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    RE: 1994 K&B .21 outboard in 2012 help

    Thanks for the great and detailed replies. Ihave yet to order my driveshafts, and Ineed to do the easy epoxy fiberglass patches for the dog bites.

    Sobie2


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