How to Install a New Powerhead on a 1979 V4 Johnson

The only V4 outboards Johnson built were the 115-horsepower Crossflow engines. These engines boasted a 99.6-cubic-inch displacement powerhead. They were built between 1978 and 1984. Because the powerhead is mounted vertically, like most smaller Johnson outboards, installation is as straightforward as it is with smaller outboards, although the V4 powerhead is heavier than the inline 3-cylinder powerhead found on smaller Johnson outboards. The process begins with the removal of the old powerhead.

Things You'll Need

  • Small adjustable wrench
  • Large adjustable wrench
  • Screwdriver
  • Pipe wrench
  • Engine hoist
  • Spreader bar
  • Torque wrench
Show More

Instructions

  1. Out With the Old

    • 1

      Loosen the nut on the shift lever, using a small adjustable wrench. Lift the shift rod to disengage it from the shift lever.

    • 2

      Remove the retaining nuts and screws from the exhaust manifold using a large adjustable wrench and a screwdriver. Disconnect the hoses connected to the thermostat and oil sump. Remove the hoses and manifold assembly.

    • 3

      Disconnect the intake manifold adapter. Disconnect the vapor separator and crankcase sump hose. Unplug the trim motor wires from their relays. Pull the wires from the front panel.

    • 4

      Unscrew the 10 bolts threaded up into the bottom of the powerhead, from beneath the engine holder, using a socket. Remove the two cylinder head nuts and their washers, located at the rear of the motor.

    • 5

      Thread two nuts onto the top manifold exhaust stud, by hand. Use the bottom nut to jam the top nut in place, with an adjustable wrench. Clamp a pipe wrench onto the two nuts and turn the nuts counterclockwise to remove the stud. Unscrew the lifting eye from the exhaust manifold, and insert it into the now-vacant stud hole. The bend of the lifting eye faces out to avoid interference between the powerhead and the engine hoist's lifting chain.

    • 6

      Place a spreader bar between the engine hoist's lifting chains. Hook the lifting chains to the lifting brackets on the front, port side and rear, starboard side of the motor. Lift the powerhead straight up, keeping it as level as you can to avoid damage to the driveshaft.

    In With the New

    • 7

      Place a new powerhead-to-engine holder gasket on the engine holder. Raise the powerhead, using the hoist and lower it to the engine holder. Align the oil pump shaft with the camshaft. Lower the powerhead onto the engine holder.

    • 8

      Seat the retainer bolt on the oil pump. Tighten the bolt to 35 foot-pounds, using a torque wrench. Bend one of the retainer tangs on the bolt up, and the other down. Thread the access bolt into the head of the retainer bolt. Tighten the access bolt to 114 inch-pounds with a torque driver. Remove the engine lifting eye. Reinstall the exhaust manifold stud.

    • 9

      Thread the two cylinder-block nuts, located at the rear of the motor, into place. Tighten the nuts to 17 foot-pounds with a torque wrench. Thread the 10 engine-holder bolts up into the bottom of the powerhead from beneath the engine holder, using a socket. Tighten with a torque wrench, to 36 foot-pounds.

    • 10

      Re-attach the intake manifold adapter, using a new gasket. Thread the nuts and bolts into place. Tighten the nuts to 16 foot-pounds of torque and the bolts to 18 foot-pounds. Re-attach the vapor separator and crank case sump hoses.

    • 11

      Reconnect the shift rod and lever. Tighten the nut to 36 foot-pounds of torque. Plug the trim motor wires into the trim motor relays and plug the wires into the front panel.