Lower Unit Service (Johnson 40 Motor)

Written By: Elijah Durkee
  • Comments: 1
Lower Unit Service (Johnson 40 Motor)

Difficulty

Moderate

Steps

20

Time Required

1 - 2 hours

Introduction

This is a three part Lower Unit Service on a Johnson 40 boat motor. Model Number: J40ELERE

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    • Remove the cotter pin that is stuck through the propeller shaft using a pair of pliers.

    • You can reinstall the old cotter pin, but it will be easier to install a new one.

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    • Using the special wrench, loosen and remove the castle nut.

    • Behind the castle nut will be a washer, set the washer on top of the castle nut to help remember the order in which everything comes off.

    • When tightening the castle nut, make sure not to block the hole for the cotter pin

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    • Remove the propeller.

    • There is another washer behind the propeller that may come off with the propeller, check for this before installing new propeller

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    • If the washer behind the propeller did not come off with the propeller, remove it and set it aside with the propeller, other washer, and castle nut.

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    • Remove the two screws on either side holding the anode in place using a 5/16 nut driver.

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    • Pull the anode out

    • Reverse the previous steps to reinstall

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    • Remove upper cowl by turning the black levers on the front and rear of the cowl

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    • Remove the lower cowl by removing the one 3/8 in bolt from the front

    • the two 3/8 in bolts from the rear of the lower cowl

    • One bolt is under the rear latch

    • the 3/8 in bolt under the bottom of the lower cowl. This is most easily done using a universal-joint socket.

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    • Trim the engine all the way up and pull the two halves away from the engine and downward, removing the rubber holders for the battery connection and control cables

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    • Remove the 3/8 in screw connecting the vertical shift linkage going into the lower unit to the horizontal shift linkage in the upper unit. This Is located directly below the block on the port side of the engine.

    • this is a special tapered bolt

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    • Remove the four 9/16 in bolts connecting the lower unit to the upper unit. This will need to be done with a regular wrench.

    • These bolts have washers

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    • Remove the one 5/8 in bolt holding the lower unit to the upper unit. This is located directly above the propeller. As you do this the lower unit will begin to pull away from the upper unit.

    • Make sure to align the shift linkage with the bracket that holds it before fully tightening the bolt

    • the lower unit may begin to slip out after this bolt is removed.

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    • Remove the lower unit from the upper unit by gently pulling the lower unit straight away from upper unit, taking care not to bend the shaft or shift linkage.

    • If the lower unit seems stuck, gently wiggle it until it comes out freely

    • 8. Place the lower unit on a table or put it up in a vice if one is available. This needs to be a clutter free workspace to ensure that the small parts in the water pump can be found if dropped

    • If you do put it in a vice, do not over tighten and use soft jaws if possible or a rag you can’t use soft jaws to protect the lower unit from being scratched or dented.

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    • Remove the four 7/16 in bolts holding the water pump to the lower unit

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    • Remove the outer water pump housing by sliding it up the shaft. This should expose the inner housing.

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    • Remove the inner housing. The impeller should be stuck tightly inside the inner housing and will come off with it.

    • The impeller has a key that holds it to the shaft that will fall out, be careful not to lose it.

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    • Remove the old impeller from the housing and install the new one.

    • Make sure the side of the impeller with the grove for the key will be facing downward when installed.

    When installing the new impeller be sure the fins are bent in the right direction so it turns with the shaft properly. If not it can damage the new impeller at start up.

    Doug -

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    • To replace the impeller and inner housing, first put the key into the notch on the shaft and slide the impeller and inner housing down the shaft lining up the key with the notch on the impeller.

    • It may be beneficial to turn the lower unit on it’s side so that gravity will hold the key in place.

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    • Slide the housing down the shaft and make sure the seal for the outer housing is sitting in the grove on the underside of the outer housing.

    • If the outer housing does not want to go over the inner housing, slowly rotate the shaft while applying gentle downward pressure to the upper housing until it slides into place.

    • To finish installation, follow the removal steps in reverse starting at step 9

Conclusion

To reassemble your device, follow these instructions in reverse order.

Author

Elijah Durkee

Member since: 12/11/21

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