Service the Water Pump in Your 3 Cylinder Evinrude/Johnson Outboard

Water pump failure can be catastrophic for your outboard motor, but it can be avoided with some basic preventive maintenance. The pump should be serviced (including impeller replacement) every two years with normal recreational use (more often in saltwater). It's something the average do-it-yourselfer can do with just a few basic tools.

Steps

  1. Remove the cowling and locate the shift rod linkage, on the port side of the power head under the bottom carburetor on the port side. On most models this is 7/16" hex-head screw. Remove the shift rod linkage screw and its lock washer, using a ratchet and short extension.
  2. Locate the shift lever and the end of the shift cable on the starboard side of the power head. Disconnect the shift lever by removing the cotter pin, and separate the cable from the lever. Tilt the motor full up.
  3. Remove the propeller nut and washer. Use a pair of needle-nose pliers to straighten then pull the cotter pin from the end of the prop shaft, then a prop nut wrench or large adjustable crescent wrench to loosen the nut.
  4. Pull the propeller off.
  5. Scribe a mark across the edge of the trim tab (so you can reinstall it in the same position). Remove the trim tab retaining bolt and trim tab. Remove the retaining bolt located in the trim tab cavity. Remove the retaining bolt from the bottom of the anti-ventilation plate. Remove the four retaining bolts from the perimeter of the lower unit, just above the anti-ventilation plate. At this point, the lower unit should start to separate from the exhaust housing.
  6. Pull the lower unit from the motor. The drive shaft and shift rod will come off with the lower unit.
  7. Secure the lower unit to your workbench.
  8. Remove and discard the rubber o-ring from near the top of the drive shaft, just below the splines.
  9. Locate the water pump. It is inside a black plastic housing bolted to the top of the lower unit, surrounding the drive shaft.
  10. Remove and discard the four hex-head screws securing the pump housing to the lower unit.
  11. Slide the pump housing, grommet and rubber gasket up the drive shaft and off. Not all models have the housing gasket. Discard grommet and gasket (if equipped).
  12. Pull the metal liner out of the plastic pump housing. There are two pieces: a flat round piece on the top, and a long rectangular piece bent into a circle. Note how there are tabs on the metal pieces that fit into slots in the plastic housing. Discard the two metal pieces.
  13. Place the replacement liner pieces from the repair kit in the pump housing.
  14. Remove the single hex-head screw holding the water tube guide in place (the water tube guide is the smoke-stack-looking thing on top of the housing) and pull the guide off. Discard the screw.
  15. Pull the rubber grommet out of the housing where the water tube guide was. Discard grommet.
  16. Insert the new grommet from the repair kit in place of the old one.
  17. Reinstall the water tube guide on to the housing using the new screw from the kit.
  18. Slide the impeller up and off the drive shaft (see Tips). Note the keyway, which is a flat spot at the bottom of the drive shaft. There will be a plastic "woodruff" key in the keyway, unless it fell out when you pulled the impeller off. The woodruff key is what makes the impeller spin with the drive shaft. Discard impeller and key.
  19. Slide the pressure plate up and off the drive shaft. Discard.
  20. Cover the drive shaft seals (where the drive shaft enters the lower unit) with an old rag or something to avoid damage from gasket remover.
  21. Spray the old gasket material with gasket remover, following the instructions on the can. Take care not to scratch or score the mating surface when scraping the old gasket off.
  22. Apply OMC gasket sealant to both sides of the new pressure plate gasket and put it in place.
  23. Put the new pressure plate in place.
  24. Note the keyway inside the hub of the new impeller because this is where the woodruff key will go when the impeller is installed.
  25. Slide the new impeller over the top and down the drive shaft, inserting the new woodruff key into the keyway just before the impeller covers it (see Tips).
  26. Apply a thin film of axle grease to the inside of the housing.
  27. Moisten the housing gasket (if equipped) with dish soap (to hold it in place) and place on the pump housing.
  28. Slide the housing over the top of the drive shaft and down to the impeller. You will probably have to reposition the gasket a few times before you are done.
  29. Force the housing down over the impeller while turning the drive shaft *CLOCKWISE* with your hand. Do not use any kind of tool on the drive shaft splines.
  30. Apply a film of OMC gasket sealant to the threads of the new housing screws (from the repair kit) and reinstall. Must be tight.
  31. Slide the new grommet over the drive shaft and push it down into place at the top of the pump housing.
  32. Slide the new drive shaft o-ring over the drive shaft and into its groove just below the splines.
  33. Apply a thin film of molly lube to the drive shaft splines.
  34. Determine which gear the lower unit is in by rotating the drive shaft *clockwise* with your hand while observing the propeller. If it's in forward the prop will turn clockwise, if it's in reverse the prop will turn counterclockwise, and if the prop doesn't turn, then it's in neutral.
  35. Shift the lower unit into reverse (if it's not already there) by firmly pushing down on the shift rod (push down two "clicks" if it's in forward).
  36. Apply a thin film of 3m #847 adhesive to the lower unit on the surface where it mates with the midsection.
  37. Align the lower unit with the midsection, and push it up into place. Make sure the shift rod goes through its hole.
  38. Rotate the flywheel *clockwise* ever so slightly to mesh the drive shaft splines with the crankshaft while pushing firmly.
  39. Apply OMC gasket sealant to the six retaining bolts and reinstall.
  40. Reconnect the shift rod linkage.
  41. Apply a thin film of axle grease to the prop shaft.
  42. Slide the prop on to the prop shaft, followed by the washer and prop nut.
  43. Tighten the prop nut, then back it off just enough to clear the cotter pinhole.
  44. Insert the cotter pin and bend one end back.
  45. Move the shift/throttle control handle into reverse position.
  46. Reattach the shift cable to the shift lever.
  47. Shift the motor into neutral.
  48. Attach muffs to garden hose, place on the lower unit over the water intakes, and turn on the water.
  49. Start the engine and look for a good strong stream of water from the telltale, indicating a successful water pump service.

Tips

  • The pump will function normally no matter which side of the impeller faces up or down, or which direction the fat end of the woodruff key is facing, but if you install it such that the fat end of the key is pushing against the widest part of the impeller hub keyway, it will be less likely to get wedged in, thus making the next removal a bit easier.
  • A good way to secure the lower unit to a workbench or sawhorse is to rest it on the anti-ventilation plate, and clamp it to the bench using a wooden clamp, or a piece of wood between the plate and a metal clamp.
  • You my find it easier to access the shift rod disconnect if the fuel line is disconnected from the fuel pump -- just loosen the thumb screw on the front of the pump, pull the front of the fuel pump housing off and push it back out of the way. Inspect the screen filter for debris.
  • If the old impeller won't come off easily, you can usually free it up by gripping the drive shaft with a wooden clamp or well padded pair of vise-grips and working it back and forth (see Warnings).
  • Wedge a piece of scrap wood between the propeller and the anti-ventilation plate to keep the prop from turning while you loosen the prop nut.

Warnings

  • The shift rod height is adjusted by screwing it in or out, so do not' spin the shift rod while the lower unit is off the motor, or you will have shifting problems.
  • Failure to apply the OMC gasket sealant (or equivalent) to the threads of all the lower unit fasteners is guaranteed to result in frozen bolts, and a major hassle down the road.
  • There is a lock washer on the shift rod linkage screw, if it falls it will end up in the exhaust housing cover, where it will not cause any problems.
  • 'Do not use any kind of tool on the drive shaft splines. If you need to grip the drive shaft for impeller removal or installation, use a wooden clamp or well padded vise-grips. The drive shaft is a very expensive precision-tooled part.
  • Gasket remover spray is a very caustic solvent; it will remove paint from most any surface, melt many plastics, and burn if it gets on your skin. Heed the warnings on the label.
  • Failure to replace the drive shaft o-ring (just below the splines) and apply molly lube to the drive shaft splines is guaranteed to result in a drive shaft that is frozen to the crank, to the point where it can't be removed without catastrophic damage to the engine.
  • Take care not to damage the grommet where the shift rod enters the powerhead compartment because if exhaust gas is allowed to bleed up into the cowling, the engine won't get enough oxygen to run.
  • Never start your outboard without supplying water to the lower unit because half a minute of dry running is enough to seriously damage the water pump impeller.

Things You'll Need

  • Ratchet, SAE sockets, extension
  • Prop nut wrench, or a large adjustable crescent wrench
  • Water pump repair kit
  • Gasket remover spray
  • OMC Gasket Sealant (or equivalent).
  • 3m #847 adhesive *or* Permatex #2.
  • Molly lube.
  • Marine axle grease.
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