- Aug 17, 2010
- 1,160
- Boat Info
- 2005 Cruisers Yachts 500 Express
Zodiac Yachtline 340DL w/ Yamaha 40 hp
- Engines
- Twin 715 hp Volvo D12s with V-Drives
In this post, I will describe the rebuilding of a late model, Mercruiser raw water pump. I will not describe the procedures needed to remove the pump from the engine, nor will I detail the impeller change - I am going to assume anyone considering a pump rebuild already knows how to perform these operations. The pump rebuild kit from Mercruiser includes a new shaft and bearing assembly, seals, snap ring, and a tolerance ring, under part #8M0050018 for the current pump.
Normally, a pump will signal the need for rebuilding by leaking raw water into the bilge. It may also start to whine or groan as the bearings fail. If these symptoms manifest, I would strongly recommend you address the issue sooner rather than later, since bearing failure can be catastrophic and sudden, leaving the engine with no source of cooling water. There is also a good chance the belt will get tossed.
So, you’ve got the pump out of the boat, and you’ve removed the mounting bracket and split the case, just as you would for an impeller change. Once the impeller is removed, the next step is pulley removal. These pulleys are pressed on at the factory with an interference fit, so you’ll need a specialty puller to remove it. If you don’t have one, many auto parts stores offer a free rental program. To provide a solid pressing surface, I thread a 3/8” - 16 cap screw into the shaft, as shown. Then, I mount the puller to the pulley, and remove the puller from the shaft.
Once the pulley is off, you’ll be left with this:
Next, take a drive punch, and carefully remove the outer seal from the housing. Tap gently all around, and be careful not to damage the housing. Don’t worry about the seal - it’s getting replaced.
Once it is out, you’ll be able to see the internal snap ring that holds the bearing and shaft assembly in place.
Using internal snap ring pliers, remove the snap ring. The bearing and shaft assembly should pop right out, but if there is some buildup inside the housing, you may have to tap it out gently. It’s a slip fit, so it shouldn’t take much to get it out.
Now, look inside the housing, and you’ll see the inner seal. Make note of the seal orientation, as they only go one way, and you need to duplicate what you find. Merc has used two different seals, so take a picture if you have to. Then, take an appropriate drift or punch, and gently tap the seal out of the housing. Be careful not to nick or damage the housing in any way.
It’s a good idea at this point to clean and paint all the parts for the housing, along with the bracket, if you have time. Otherwise, clean all the parts, dry thoroughly, and move to reassembly.
First, lightly oil the perimeter of the new seal, and drop it into the pump housing in the same orientation you noted previously. There are instructions for seal orientation that come with the replacement parts in the kit, so follow them closely. You do need a tool to press the seal in place, and for this I use a 1.25” solid steel shaft. A piece of plastic round stock would also work, or you can use an appropriate old bearing race, but it has to be something flat, and just a hair smaller than the seal bore. Press the seal in place until it bottoms in the bore.
Next, lightly oil the outside of the new bearings (the new bearings come already pressed on the new shaft), and also lightly oil the end of the shaft that will pass through the inner seal, and the housing interior. Just apply a very light film with your finger, not a heavy coat, then slide the new shaft into place, and carefully guide it through the seal. With just light pressure, the assembly should bottom out in the housing, exposing the snap ring groove. Install the new snap ring.
Take the new outer seal, and apply a light coating of sealant to it, as described in the instructions. Using an appropriate mandrel or tubing, gently seat the outer seal in the housing.
The last step is the reinstallation of the pulley. The instructions describe how to do it with a pulley installation tool, but I prefer using a press. If you do use a press, be sure to apply pressure only to the shaft, not the bearings. Once the pulley is seated, the remaining assembly of the pump is the same as for an impeller change.
Normally, a pump will signal the need for rebuilding by leaking raw water into the bilge. It may also start to whine or groan as the bearings fail. If these symptoms manifest, I would strongly recommend you address the issue sooner rather than later, since bearing failure can be catastrophic and sudden, leaving the engine with no source of cooling water. There is also a good chance the belt will get tossed.
So, you’ve got the pump out of the boat, and you’ve removed the mounting bracket and split the case, just as you would for an impeller change. Once the impeller is removed, the next step is pulley removal. These pulleys are pressed on at the factory with an interference fit, so you’ll need a specialty puller to remove it. If you don’t have one, many auto parts stores offer a free rental program. To provide a solid pressing surface, I thread a 3/8” - 16 cap screw into the shaft, as shown. Then, I mount the puller to the pulley, and remove the puller from the shaft.
Once the pulley is off, you’ll be left with this:
Next, take a drive punch, and carefully remove the outer seal from the housing. Tap gently all around, and be careful not to damage the housing. Don’t worry about the seal - it’s getting replaced.
Once it is out, you’ll be able to see the internal snap ring that holds the bearing and shaft assembly in place.
Using internal snap ring pliers, remove the snap ring. The bearing and shaft assembly should pop right out, but if there is some buildup inside the housing, you may have to tap it out gently. It’s a slip fit, so it shouldn’t take much to get it out.
Now, look inside the housing, and you’ll see the inner seal. Make note of the seal orientation, as they only go one way, and you need to duplicate what you find. Merc has used two different seals, so take a picture if you have to. Then, take an appropriate drift or punch, and gently tap the seal out of the housing. Be careful not to nick or damage the housing in any way.
It’s a good idea at this point to clean and paint all the parts for the housing, along with the bracket, if you have time. Otherwise, clean all the parts, dry thoroughly, and move to reassembly.
First, lightly oil the perimeter of the new seal, and drop it into the pump housing in the same orientation you noted previously. There are instructions for seal orientation that come with the replacement parts in the kit, so follow them closely. You do need a tool to press the seal in place, and for this I use a 1.25” solid steel shaft. A piece of plastic round stock would also work, or you can use an appropriate old bearing race, but it has to be something flat, and just a hair smaller than the seal bore. Press the seal in place until it bottoms in the bore.
Next, lightly oil the outside of the new bearings (the new bearings come already pressed on the new shaft), and also lightly oil the end of the shaft that will pass through the inner seal, and the housing interior. Just apply a very light film with your finger, not a heavy coat, then slide the new shaft into place, and carefully guide it through the seal. With just light pressure, the assembly should bottom out in the housing, exposing the snap ring groove. Install the new snap ring.
Take the new outer seal, and apply a light coating of sealant to it, as described in the instructions. Using an appropriate mandrel or tubing, gently seat the outer seal in the housing.
The last step is the reinstallation of the pulley. The instructions describe how to do it with a pulley installation tool, but I prefer using a press. If you do use a press, be sure to apply pressure only to the shaft, not the bearings. Once the pulley is seated, the remaining assembly of the pump is the same as for an impeller change.
