Many of us have the little Honda BF5, 5 HP 4-stroke outboard on our boats. It's not too difficult to replace the water pump assembly yourself and save a bunch of money! I did this project in about an hour, including the time to take some photos of the project.
Now I probably could’ve only replaced the pump impeller, but I purchased the motor used last year, and now I know exactly where I’m at with the water pump.
Here are discriptions of the attached photos from the project. Hope it will help someone out there that is anticipating this project.
1. Lower unit of the Honda BF5, or as we call it, the 5 HP little Honda many of us use on our boats
2. Closer view of where we'll start the project. Ever wonder that this black rubber thing was? It covers the hole where the shifting rod attaches to the shifting rod in the lower unit
3. The rubber plug is removed and you can see the shifting rod going up to the shifting lever on the side of the motor. Loosen the 10mm bolt, only loosen! Don't remove it. I placed the engine in forward to raise it up a little to get at the bolt easier.
4. There are 2-10mm bolts that hold the lower unit onto the engine. They are both in the middle, one being in the very front, and the other above the prop in the center of the cavitation plate. The bolts are the same length, so no worry about getting them mixed up.
5. Once the bolts are removed, gently, and I mean VERY gently, tap around the top of the cavitation plate to remove the lower unit assembly. Use a piece of wood and tap around with a small hammer at the area where the cavitation plate comes from the housing.
6. The lower unit assembly is now free of the engine, exposing the water pump assembly.
7. Looking down at the water pump assembly. The black tube is where the water comes out going up to the engine. The square piece is the drive shaft from the engine to the lower unit, and the shifting rod sticking up.
8. The water pump assemble has been removed. It was held on with 4 10mm bolts, all of the same length. The kit supplies new bolts. Take special notice of the rotation of the pump impeller. It rotates counter-clock-wise. I just left this all together for future reference.
9. This photo shows the pump assembly removed. We're going to take off the gasket and the bottom plate of the water pump system.
10. Everything has been removed, and I wiped the shaft clean, and took a small brass wire brush to clean up any salt deposits. I always flush the engine when we pull the boat, and the lack of salt deposits is evidence.
11. A new gasket supplied in the kit is installed. There are two of these supplied in the kit, and they are the same, and only go on one way. There are two alignment tabs to ensure you can’t screw it up.
12. The SS bottom plate is installed now. It too can only be installed one way. It's impossible to install it wrong.
13. On top of the SS pump plate goes the other gasket. Again, impossible to install it wrong.
14. I sprayed some Simple-Green soap on the new impeller and in the new housing. Remember impeller rotation? I took a rag and a large screw driver and turned the impeller CCW as I fit it into the new pump housing. Pay attention to the location of the flat section on the shaft that lines-up with the flat section on the impeller. This will make re-assembly a lot easier if you pay attention to the small details.
15. New housing with the impeller installed next to the old assembly. Notice the impeller vanes are in the same rotation.
16. The new water pump assembly is mounted back onto the lower unit. The kit comes with 4 new ferrules to go in the 4 bolt holes, and new bolts with a yellow lock-tite mixture already applied. Install the 4 SS ferrules in the mounting holes and the bolts, tighten snug, and of course cross tighten the bolts as you go.
17. This photo shows the new bolts with the lock-tite already applied.
18. Looking up the engine shaft. The square tube is for the drive shaft to go in, and the tube above it is the water tube to the engine. I gave a light coat of grease to the drive shaft to help keep corrosion from forming at this joint. This is probably the most difficult part of the job. Re-assembly. Note the square shaft position. You'll want the shaft on the lower unit in the same position, and remember CCA ONLY rotation to align it. I also sprayed some Simple Green soap on the tube and the rubber seal on the water pump assembly,(this is the tube that carries the engine cooling water up), this just makes it all slide together easier.
19. Gently slide the lower unit assembly up, and make sure the shifting rod goes back in. I used a small screw driver and some needle-nose pliers to get it back in alignment. Gently tap the unit up, and install the two long 10mm bolts with just a drop of medium strength lock-tite on the threads. Tighten the 10mm bolt snug. It helps to spray the black rubber plug with some soap, (I used Simple-Green), and replace it back on the motor.
After everything is back together, I pulled the ignition lock so the engine wouldn’t possibly start, and pulled the engine thru several times to make sure nothing was stuck. And remember, never ever, ever, ever, start the engine dry!
Don Boyko
s/v “Y-Knot?”
San Diego, CA
Now I probably could’ve only replaced the pump impeller, but I purchased the motor used last year, and now I know exactly where I’m at with the water pump.
Here are discriptions of the attached photos from the project. Hope it will help someone out there that is anticipating this project.
1. Lower unit of the Honda BF5, or as we call it, the 5 HP little Honda many of us use on our boats
2. Closer view of where we'll start the project. Ever wonder that this black rubber thing was? It covers the hole where the shifting rod attaches to the shifting rod in the lower unit
3. The rubber plug is removed and you can see the shifting rod going up to the shifting lever on the side of the motor. Loosen the 10mm bolt, only loosen! Don't remove it. I placed the engine in forward to raise it up a little to get at the bolt easier.
4. There are 2-10mm bolts that hold the lower unit onto the engine. They are both in the middle, one being in the very front, and the other above the prop in the center of the cavitation plate. The bolts are the same length, so no worry about getting them mixed up.
5. Once the bolts are removed, gently, and I mean VERY gently, tap around the top of the cavitation plate to remove the lower unit assembly. Use a piece of wood and tap around with a small hammer at the area where the cavitation plate comes from the housing.
6. The lower unit assembly is now free of the engine, exposing the water pump assembly.
7. Looking down at the water pump assembly. The black tube is where the water comes out going up to the engine. The square piece is the drive shaft from the engine to the lower unit, and the shifting rod sticking up.
8. The water pump assemble has been removed. It was held on with 4 10mm bolts, all of the same length. The kit supplies new bolts. Take special notice of the rotation of the pump impeller. It rotates counter-clock-wise. I just left this all together for future reference.
9. This photo shows the pump assembly removed. We're going to take off the gasket and the bottom plate of the water pump system.
10. Everything has been removed, and I wiped the shaft clean, and took a small brass wire brush to clean up any salt deposits. I always flush the engine when we pull the boat, and the lack of salt deposits is evidence.
11. A new gasket supplied in the kit is installed. There are two of these supplied in the kit, and they are the same, and only go on one way. There are two alignment tabs to ensure you can’t screw it up.
12. The SS bottom plate is installed now. It too can only be installed one way. It's impossible to install it wrong.
13. On top of the SS pump plate goes the other gasket. Again, impossible to install it wrong.
14. I sprayed some Simple-Green soap on the new impeller and in the new housing. Remember impeller rotation? I took a rag and a large screw driver and turned the impeller CCW as I fit it into the new pump housing. Pay attention to the location of the flat section on the shaft that lines-up with the flat section on the impeller. This will make re-assembly a lot easier if you pay attention to the small details.
15. New housing with the impeller installed next to the old assembly. Notice the impeller vanes are in the same rotation.
16. The new water pump assembly is mounted back onto the lower unit. The kit comes with 4 new ferrules to go in the 4 bolt holes, and new bolts with a yellow lock-tite mixture already applied. Install the 4 SS ferrules in the mounting holes and the bolts, tighten snug, and of course cross tighten the bolts as you go.
17. This photo shows the new bolts with the lock-tite already applied.
18. Looking up the engine shaft. The square tube is for the drive shaft to go in, and the tube above it is the water tube to the engine. I gave a light coat of grease to the drive shaft to help keep corrosion from forming at this joint. This is probably the most difficult part of the job. Re-assembly. Note the square shaft position. You'll want the shaft on the lower unit in the same position, and remember CCA ONLY rotation to align it. I also sprayed some Simple Green soap on the tube and the rubber seal on the water pump assembly,(this is the tube that carries the engine cooling water up), this just makes it all slide together easier.
19. Gently slide the lower unit assembly up, and make sure the shifting rod goes back in. I used a small screw driver and some needle-nose pliers to get it back in alignment. Gently tap the unit up, and install the two long 10mm bolts with just a drop of medium strength lock-tite on the threads. Tighten the 10mm bolt snug. It helps to spray the black rubber plug with some soap, (I used Simple-Green), and replace it back on the motor.
After everything is back together, I pulled the ignition lock so the engine wouldn’t possibly start, and pulled the engine thru several times to make sure nothing was stuck. And remember, never ever, ever, ever, start the engine dry!
Don Boyko
s/v “Y-Knot?”
San Diego, CA
