My Yanmar 1GM10 developed, over the last few years, a leaking water pump. I instituted some ‘stop-gap’ repairs, such as cleaning out the pump, installing a new impeller, putting a new o-ring on the Speedseal Cover, cleaning out the hoses and water passages, replacing the thermostat, etc. The real problem was bad seals. I made the decision to rebuild the pump instead of replacing it ($185).
The leaking water pump dripped salty water down onto the exposed oil pipes running below the pump, eventually causing them to rust through and allow the engine to pump oil into the sump below. Luckily, the engine was stopped before any damage was done. Replacing the pipes is not cheap. A new set of 3 is about $130, from Marine Diesel Direct (Torresen Marine). The pipes are thin steel and will start rusting immediately, if not painted and kept dry. I decided to replace these also.
What I was putting off all this time was removing the water pump and rebuilding it, with new seals ($5.23 each) for the water and oil side. To accomplish this, the flywheel must be removed. This requires a torque wrench or breaker bar, and a wheel puller. Both tools were in my inventory at home, but, as I said, the work was put off for simpler solutions.
The crankshaft nut in front of the flywheel is torqued on to about 72 Ft-lbs. It’s almost impossible to get off without a torque wrench or breaker bar. Additionally, you need to stop the pulley from turning with an attached anti-rotation bar (see pics). While trying to break the nut free, I was crouching in front of the engine with most of my weight on the bar. It broke free suddenly, causing me to fall and hit my head on the edge of the aft berth. When I opened my eyes, I couldn’t focus for a few seconds. I had apparently knocked myself ‘senseless’ in the process…so be careful!
Once the nut is off, you need to get the flywheel off with a wheel puller. I wouldn’t recommend hitting it with a hammer, as you might bend the pulley or damage the crankshaft. When I put the wheel puller on, and tightened the screw, it tightened, but didn’t come off. I decided to stand up and put my weight into it, as before. While standing up, the pulley, with puller, popped off and fell into the bilge. Luckily, there were enough hoses in the cavity to stop its downward travel, and make retrieval easy.
Now that the pump was exposed, removal should be easy, right? Wrong! I waited too long…all three holding bolts had rusty heads which crumbled inside the box wrench I was using to get them off. Even a slightly smaller socket would not work. The only solution was to drill the bolt head out and insert an easy out. This done, all three bolts were removed without further problems.
With the water pump removed, the weep holes, bearings and shaft, and internal seals can be easily examined. The bearings appeared to be in good shape, along with the drive shaft. Some clean-up was performed with bronze wool.
The rubber coated seals were driven out with a wooden dowel rod, tapping around the two seals with a small hammer. Normally, the seals can only be installed, and removed, one time, as they are usually destroyed in the removal process. More on this later.
With the seals out, the pump casting was cleaned thoroughly in a vinegar bath, and examined for any nicks or burrs, and cleaned up.
Putting the new seals in was basically step by step in reverse. The smaller, water seal goes in first, open side down. This was tapped in with an appropriate sized dowel rod until it stopped. The larger, oil seal goes in next, open side up. This seal must be installed carefully, because there is no stop behind it; if you drive it in too far, it will start coming out the back, into the open space where the weep holes drain. I made this mistake, and had to consider how to retrieve the seal without damaging it. I was out of time and did not want to wait for another new seal via mail. What to do?
The solution was to make an ‘oil seal puller’…this was accomplished by grinding a bolt head down, splitting it to fit thru the shaft hole, making some thin split washers that fit thru the weep holes and around/under the puller T head, and apply pulling pressure at the threaded end via a plate with hole over the opposed end on the pump casting. After spending two days making the puller, it took 5 minutes to extract the oil seal with no apparent damage…it was subsequently installed in its proper position.
The bearings/shaft assembly was soaked in kerosene, and then re-packed with grease and inserted into the pump casting. A circlip, removed earlier, holds the bearings in place.
The remaining re-installation went quickly. The rebuilt pump was attached with three new plated bolts, and new oil pipes were painted and bolted into position.
The cleaned and painted flywheel was pushed onto the tapered crankshaft, and the nut spun on and torqued back to specs. Note that the ‘anti-rotation bar’ position had to be changed to accommodate the clockwise tightening direction.
The ‘smoke test’ is always the culmination of an amateur mechanic’s effort. Witness the running of the completed engine. No Leaks! Of course, if you have a trusted mechanic at the boatyard to perform all the above steps, you only have to pay $85/hr. to have him do it. My problem with that is that paid hourly work inevitably leaves you with less information about your engine than if you had your own hands on it. But, even I have paid for boatyard work, to save time, so, to each his own!
