Nanni N4.38 Raw Water Pump Replacement

 Why?

The original raw water impeller pump in the Nanni N4.38 engine is a Johnson Pump 10-24334-01, which is known to develop a leak prematurely at the seal. Other Vision 444 owners have had to replace these original pumps after between 300 and 1000 hours, when they start to leak.

Fortunately, Johnson has created a 10-24334-11 part number that supposedly corrects this problem.  

Parts, tools and supplies you will need

• a new Water pump or two, preferable the 10-24224-11 model.
  We ordered ours from marinepumpdirect.com for ~$250 each.  If they are not in stock, email them at info@marinegate.com.
• a 27mm deep, 6 point socket.  
  You don't need a super quality one; it's just to remove the hose barb. Trust me, you need a socket.
• Ratchet (likely a 1/2" drive) for above.
• Screwdrvier or nutdriver to remove the hose clamps
• Hose Remover Tool
  Optional, but super helpful all over the boat to break the seal when removing hoses!
• Teflon tape
  This can be white or yellow (thicker, usually for gas), or thread sealant.
• small metal pick to clean old sealant from hose barb threads
• 5mm Allen wrench (pretty sure it was 5mm)
• A clean rag to clean up the rigid gasket between the engine block and the water pump.
• A container to catch the water that dumps from the water hoses.
• 30 minutes of time per engine.
• Blue enamel engine paint
  Optional: "Ford Blue" is a somewhat close match, though the Nanni blue is softer and metallic flake.
• Alcohol swabs, or rubbing alcohol and lint-free rags
  Optional, if you are painting them.

Preparation

If you want to paint the water pump(s) before installing them, give them a quick wipe with an alcohol swab, and then tape off the back side of the mounting plate.  Also, take small piece of tape to cover the openings where the stainless shaft is visible.  

Two medium thickness coats with a fast-drying engine enamel are very easy to apply.  Usually, you will wait about 30 minutes between coats, but check the instructions for your paint. You will likely not need to wait the full cure time before installing them, especially since the pumps will not see high heat.

The install is best done with a cold engine, as it will be more comfortable to work and less oil will drip from the water pump connection area.

Open the engine bay and situate the tools where you can reach them all.

There will be some oil dripping from the old pump, so have a box or piece of cardboard on which the pump can bet set.

Detailed Steps

Removal

1. Turn off the raw water through-hull on the the saildrive.
2. Loosen the hose clamps on the raw water pump hoses.
3. If you have one, use the hose remover tool, inserted between the hose and barb to break the seal and make removal easy.
4. Remove the hoses and hold over a container to catch the seawater.
5. Use your 27mm socket and ratchet, to remove both hose barbs.
   If they start to back-out and then get difficult again, re-tighten slightly and then loosen again.  Repeat this until the removal becomes easy.  You are doing this to work the old sealant out of the threads and preventing the hose barb from breaking.
6. When removed, clean all residue from the hose barb threads, then apply thread sealant or Teflon tape (applied clockwise when viewing the hose barb threads first).
   
   

   

   Hose barb ready for installation

   
   
7. Remove the four allen head bolts that hold the pump to the engine.  Ours took almost no force to remove.
   BE VERY CAREFUL, EACH ONE HAS A WASHER AND IT IS VERY EASY TO DROP THEM!!
8. Pull the pump out of the engine block, and set on your cardboard, with the shaft pointing up.
   
9. Carefully remove the gasket that is likely stuck to the backside of the pump flange. It is mostly blue enamel that is holding it on.
10. Clean the gasket thoroughly.
    Our gaskets had oil residue and paint overspray; both of which easily rubbed off with a cotton rag.

Installation

1. Wipe up the small drip of oil that is below the pump opening.
2. Place the cleaned gasket on the new pump.
3. You are now going to install the new pump to the block, but there are several things to keep in mind:
1. The orientation of the pump.  It points off to the right as you sit and face the engine.
2. Check the old pump to find the pump mounting holes to use (they are upainted)
3. VERY IMPORTANT: You will need to rotate the pump once you find one of the two orientations possible for the shaft to mate into the engine.
   YOU MUST ONLY ROTATE THE PUMP COUNTER-CLOCKWISE to get to the proper pump alignment. If you rotate clockwise, you will force the impeller vanes to point the wrong direction, which can damaged them, plus they will get reversed again when you start the engine the first time.
   A tip for this is to start with the pump with it's connection pointing to the left.  Slowly turn Counter-Clockwise until the shaft seats into the engine.  Once is does, continue to turn the pump housing Counter-Clockwise until the alignment is correct.
4. Once the alignment of the pump is correct, you will likely have to remove the pump to get the gasket to line up with the correct holes.
   It is a little bit of a challenge to get the gasket and pump lined up and get the first screw and washer started.
5. Once the first screw is started, use the allen wrench to barely tighten all screws.
6. Then, using a rotating patten (1,3,2,4), fully tighten all screws.
   You should not have to strain to do this, but they should be fully tight.
   
   

   

   New pump mounted!

   
   
7. Now that the pump is mounted, install the hose barbs.
   Start by hand until they are properly threaded.
   If you are using Teflon tape and they thread very easily, apply more Teflon tape as they should be hard to thread by hand.  If you are using sealant, they may be easy to install, but the sealant will set and create a watertight seal.
   
8. I tightened them to about 30 ft-lbs of torque.  These are not NPT threads, so they don't taper and automatically tighten.  You will have to fully tighten the barbs until the hex area is tight against the pump body.
9. Once both hose barbs are tightened, re-install the hoses and fully tighten all four hose clamps.
   MAKE SURE, the hose coming from the engine goes to the top hose barb!
10. Open the raw water through-hull at the saildrive.
    It's not a bad idea to slightly loosen the water-strainer to purge some of the air from the system. Tighten the filter lid when the filter bowl is filled with water.
    
    

Test

Now that the new pump is installed, start the engine and make sure that everything is functioning and there are no leaks.

1. Start the engine.
2. Check to make sure that water is flowing.
   You can check the filter housing or the exhaust outlet for the engine,
   
1. If not, stop the engine immediately and find out why!
3. Observe the pump and hoses to check for any drips.
4. Allow the engine to run for at least 30 seconds.
   Checking at higher RPMS is a good idea, but allow the engine to warm up for two minutes before increasing RPMS.
5. Turn of the engine and more thoroughly check for leaks.  You can press your finger to the bottom of the pump and hoses to see if there is any water.

Celebrate!

You did it and probably saved yourself a couple hundred dollars.

Crack open your favorite celebration beverage of choice!

Final Thoughts

These pumps are very serviceable and the actual body will likely never need to be replaced (at least on the -11 pumps; I have no idea what was "wrong" or changed on them from the original -01 models)

The seal, inside wear plate, outside wear plate (cover) and shaft can all be replaced.

I have not done a tear down on one yet to see how much trouble this is, but plan to with the two failing pumps.  I may keep them as spares, but heard they will continue to eat seals and leak, so I'm not sure it's worth putting much into them.

Your thoughts?

Please take a moment to pass on any thoughts or knowledge on the pumps, the process or my article!

Thanks for reading!