In sailing, one of the most magical moments, is hoisting your sails, and enjoying the peace that comes with shutting down the engine. This past week, however, nothing was more magical than hearing Gemini‘s Universal M18 roar to life. When Mrs. Gemini and I started looking for a new boat, the one aspect I was unwilling to compromise on, was that I wanted a boat that didn’t need any engine work. As it turns out, I compromised.

When Mrs. Gemini and I were looking at Gemini, I briefly, visually inspected the engine, but never tried to start. I inquired as to whether it ran, and the previous owner had told me that when he bought the boat, the engine was started at the dock, once. The owner before him had broken the dipstick tube, and rather than replace the part, they simply covered the gaping hole with Marine Tex epoxy putty.

Marine Tex is great product for filling in small holes in the fiberglass, but I would argue that it isn’t the best product for fixing an engine oil leak. When they tried to plug up the leak, they didn’t clean the bonding surface very well, which resulted in a poor bond, and more oil leaking. I’d like to tell you that they went ahead and made the proper decision then to replace the tube, but they didn’t. When the first layer of Marine Tex still let out the life blood of that little diesel, they figured a second layer would do the trick.

Once again, without cleaning the surface free of oil residue, they applied more putty. I don’t know how many layers in total they applied, but when we purchased Gemini, she had her entire oil pan, bottom of the bell housing, and part of the front timing cover entirely encased in Marine Tex. She was also still leaking oil. It was upon a deeper inspection that I decided the best course of action was to remove the engine to clean the putty off.

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It was a cool November day when I made that decision, and it has been a long 6 months to get it to the point of running again. With the help of my good friend, Eric, we removed the engine from it’s perch on November 12th, 2018. With the engine on the cabin sole, we were able to get a good look at just how much putty was applied, and it was truly astonishing. With a hammer and a chisel, we began chipping away layer after layer of Marine Tex. It looked like the rings of a tree, putty, oil, putty, oil; you get the idea.

While removing over $100 worth of Marine Tex, I noticed that I was able to turn the crankshaft by hand, with little to no resistance. This, coupled with the fact that the engine was already removed, lead me to the decision that the little Universal M18 was going to be fully rebuilt. With the help of my sailing friends, Eric, Kendall, Brandon, and Doug, we lifted the engine, by hand, out of the cabin, up the marina dock, and loaded it in the back of my truck.

Back home, in my garage, the tear down process began. It was covered in 30 years of oil, grease, and diesel. A visual inspection of the cylinders, pistons, and other components didn’t show any catastrophic issues, just normal wear and tear. I decided that if I was putting this much effort into a proper rebuild, I should have the internal components inspected by a machine shop anyway, as well as have them rebuild the head for me.

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The Universal M18 engine is, under all that bronze paint, a Kubota engine. The M18 is a Kubota Z600 long block, which can be found on a Kubota B4200D tractor, with the mechanical fuel pump replaced by a raw water pump and painted a new color. When it came time to order new internal components, piston rings, bearings, valves, and most of the gaskets, I was able to purchase them through my local Kubota dealer and pay 1/3 less than ordering the “marine” parts from Westerbeke/Universal.

The machinist had the parts for a couple weeks, and in that time, I was able to clean some of the external components. As I stated earlier, the entire engine was dirty. Eric has a media blasting cabinet, and was good enough to let me borrow it. I loaded up a box of parts, and headed over. For three hours, we sand blasted, wire wheeled, sanded, and cleaned up everything, and even added a fresh coat of paint.

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When I removed the raw water pump, a few little black “rocks” fell out of it. Curious as to what those could be, I took off the impeller cover, and was dumbfounded at what was inside. The old impeller had dry rotted, broken, and had turned into little rubber marbles, fully blocking the pump. On top of that, the pump must have been leaking at one point, as a previous owner Marine Tex’ed the base of it to the timing cover. This trapped salt water between the aluminum timing cover, steel studs, and bronze water pump, corroding the timing cover. Electrolysis actually burned a hole in the timing cover, which I needed to have welded before I could reinstall it.

With the engine back from the machinist, and new parts delivered, I put the little diesel back together. I installed all new bearings, piston rings, oil seals, and a full gasket set. Another fresh coat of paint, and the engine was ready to go back to its home. But before installing
I used the opportunity to clean and apply a fresh coat of paint to the engine bay. Once again, 30 years of dirt, oil, and diesel resulted in an ugly looking bilge.

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I loaded the engine into the back of the truck once again, and drove out to the marina. Once again, Eric was there to lend a hand, and together, along with my marina owner, we got the engine back into the boat. We put the engine back in the bay, and I let out a sigh of relief. The rebuild process had taken a long five months to get to this point, and the finish line was finally in sight. I wrote down my punch list, and slowly crossed off every single item.

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The final part of the rebuild, was finally starting the engine. I had never owned a diesel before, much less rebuilt one. I’ve rebuilt a lawn mower engine prior to this, so I was confident in tackling this chore. However, my ignorance of diesels proved frustrating the first time I tried to start the engine. With an audience at the dock, I was below bleeding the fuel lines of air, while Mrs. Gemini was ready at the starter button. She pushed the button, the started spun the motor, and spun the motor, and spun the motor. The engine wouldn’t start. I troubleshot the motor for what felt like an eternity before calling it a night.

Two nights later, on April 17, 2019, I returned to Gemini and tried again. I tested the glow plugs and found that they weren’t getting voltage, so I removed all the electrical connections, sanded them, and reinstalled. Back in the cockpit, I hit the starter and she just continued to spin. Losing faith in my rebuild, I tried one more time to get the motor to start. After five seconds of nothing, the engine coughed, disengaging the starter. With the a glimmer of hope, I tried again, and this time, the engine breathed to life.

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The idling diesel was a magical sound that I had been anxious to hear for 6 months. It was rewarding and excited and I called Mrs. Gemini right away to let her hear it over the phone. This was a project that I had not wanted to undertake, but having done so, I learned invaluable knowledge of my engine and have confidence in it for the next 30 years.