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1972 Evinrude 50 HP "Lark". New motor, new challenges

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  • 1972 Evinrude 50 HP "Lark". New motor, new challenges

    I finally had an offer come along on craigslist that I thought was too good to refuse. A fellow out here had a 1972 Chapparal 15' tri-hull that he had to get rid of due to moving to a new community that would not let him keep a boat (townhouse community, no garages). I picked up this boat for $400. It has a 72 Evinrude 50 HP "Lark" (Model 50273C). I tested compression (140 on both cylinders) and spark (good bright spark with a tester), checked the LU oil, which came out blackish, but did not show any water mixing, nor did any water come out of the LU.
    I have the service manual on order already, but just wanted to see if anyone had any words of warning about working on these motors. I see that it does not have a manual shift, but some kind of push-button arrangement.
    I cranked the motor to test compression and spark, but did not actually start the motor. The fellow didn't have a barrel to run it in, so given the price I paid I am taking a chance. I figured with those compression numbers and the spark test, If it doesn't run it would be a fuel/carburetor issue which doesn't worry me too much since my first step will be to disassemble, inspect, and clean the carbs and replace the fuel lines.

    I have had older motors up to now which are not able to use muffs. Can this motor run on muffs?

    Any words of wisdom would be appreciated.


    1988 Stingray 176 SVB with Mercruiser 3.0L (181 CID) - The Ghostrider
    1995 Seadoo SPX 657x Rotax

  • #2
    Re: 1972 Evinrude 50 HP "Lark". New motor, new challenges

    Uhhhh..... I have a '73 65hp and I run it on the muffs all the time. Get ya some and see if the motor will run. Wouldn't surprise me if it needed a carb job.
    15.5 fiberglass CC, 1973 65 hp E'rude "the beast"


    • #3
      Sign up today
      Re: 1972 Evinrude 50 HP "Lark". New motor, new challenges

      you have good power head, but you have a hydro-electric shift lower unit. i had a 71 did not like running on muffs, best in barrel.

      notice the difference in the lower unit oil, it requires special oil.

      Hydro Electric Shift)
      (J. Reeves)

      The shifting setup of the lower unit is what's called a "Hydro Electric Shift", which is quite complex consisting of voltage being applied to solenoids in the lower unit which in turn change oil passages via a oil pump that supplies various pressure on a spring loaded shifter dog. The wires leading to the lower unit (at the powerhead) are "Green" and "Blue". The engine must be running or cranking over in order to shift out of forward gear.

      You CAN NOT use HI VIS lube in that lower unit. You MUST USE what OMC calls "Premium Blend" lube, commonly called "Type C". (A thinner lube)

      In neutral, you need 12v to the "Green" wire.
      In reverse, you need 12v to both wires, the "Green" one and the "Blue" one.
      In forward, there should be no voltage to either wire. (The spring loaded shifter dog forces the unit into forward gear)

      To check the lower unit for proper shifting to make sure you have no trouble there, remove the spark plugs to avoid problems and to allow a higher cranking speed.

      This next step eliminates the actual shift switch in case problems may exist there.... Disconnect the blue & green wires at the knife connectors (the rubber insulated boots) leading to the lower unit at the powerhead, then using jumpers, take voltage direct from the starter solenoid to apply voltage to the "Green" wire for neutral, then both wires 'Green" & "Blue" for reverse (Remember the engine must be cranking over in order to shift).
      With no voltage applied, the unit should be in forward. No need for a ground jumper... the lower unit's already grounded. You may crank the engine with the key switch or by energizing the starter solenoid with a jumper wire.

      also when servicing the water pump be very careful of the wires, and the grommet has to be in place or the carbs will suck exhaust thru the wire opening.
      TEBOW Country

      Please, NO PM's (Private Messages) regarding boat/engine problems. they will not be answered.
      That is what these forums are for. Post your questions, in the appropriate Forum.