Rebuilding a Marine Diesel Engine

The Break Down

I find it ironic that we have spent the first six months as owners of our Cheoy Lee 38 sailboat worrying about, tinkering with, and ultimately rebuilding our inboard diesel engine. My purist, environmental, thrifty, romantic side is inclined to tear it right out and free up a tremendous amount of time, money and storage space. My practical side and my wife (which are often one and the same) were not so sure. There were many a late-night discussion on just this topic before even owning our latest boat became a reality.

Upon the initial inspection of our boat, we discovered she contained the original 35 year old Perkins 4-108 diesel with no hour meter installed. It ran smoothly but would quickly overheat after starting.  This issue was solved by cleaning the heat exchanger with an acid bath to remove decades of built up sediments. In January, we moved the boat from Titusville, FL northward on the Intercoastal Waterway (ICW) bound for Green Cove Springs Marina, twenty miles south of Jacksonville on the St. John’s River.

During the trip, the engine began to emit a sharp knocking sound that, not long after, lead to its total failure just south of the Beach Boulevard Bridge in Jacksonville Beach on the ICW. Hoisting the sails was not an option as we  had a 2 knot following current with a 5 knot headwind in a confined channel so we anchored. We determined that a tow was our only option before darkness set in. Fortunately, we were less than a mile from Palm Cove Marina. Even still, the Tow Boat US bill was over $200! Once tied to the docks at Palm Cove Marina, we had some decisions to make. All of those discussions about sailboats and engines had just become very pertinent.

Attempting to diagnose engine failure while at anchor in the ICW

In the end, we decided the most practical thing to do was keep the engine but not become a slave to it. We intend to spend at least this coming winter in Florida with its many narrow inlets, anchorages and bridge barricaded ICW. Not having an engine would definitely limit our ability to navigate these areas. We would also be working and be tied to schedules that demand we return to our home port at a set time regardless of wind speed and direction. We also decided that removing the engine would definitely reduce the resale value when we eventually part ways with the boat.

With this being said, we vowed to keep the engine in its rightful place aboard the ship, as a useful auxiliary mode of propulsion. We will primarily move the boat with the sails as intended whenever possible.  We will become proficient as a crew/family at maneuvering under sail to and from a dock, mooring, anchor and man overboard. The engine is a very powerful and useful tool but should not be the only option available to get the boat from A to B because, as we have experienced, it does and will fail.

If we were going to put up with the noise, pollution, weight and expense of the engine then we determined that it must be as reliable as possible and that we should know how to repair every part of it. Sitting at the dock in Jacksonville Beach we decided to remove the 600+ lb engine from the boat using the marina’s forklift and haul it back to Vermont in a rented U Haul trailer. I would rebuild it over the winter and return in the spring to reinstall it and move the boat the remainder of the distance to Green Cove Springs. The major factor leading to this plan was access to our neighbor’s well equipped, heated garage in Vermont.

Being a farmer requires that you are at least a little bit knowledgeable in a broad range of disciplines from carpentry and mechanics to electrical work and plumbing. This is usually due to the lack of money available to pay someone that actually knows what they’re doing. I’ve often said that I know just enough to be dangerous. I have always repaired and maintained our vehicles but never tackled a mechanical job as big as rebuilding an engine. But, under the wing of my neighbor, Old Bill (who bears a striking resemblance to Santa Claus in blue denim overalls), I was determined to give it a shot.

The Rebuild

The trip up I-95 to Vermont was uneventful though the tolls for a vehicle towing a trailer were outrageous! The first step was to disassemble the engine and determine what killed it. I was careful to have a supply of Ziploc baggies on hand and label every bit and piece that I removed, a step that I was grateful for later. After doing some research, I found that the Perkins-4108 is widely used as an auxiliary engine and has a good reputation for reliability. I found it to be a fairly simple engine to work on with the head mounted right atop an engine block containing four in-line cylinders.

Disconnecting the transmission and bell housing was pretty straight forward as was the front end with only four gears (crankshaft, camshaft, injector pump/raw water pump, and idler). The cause of death was finally determined when we had the engine upside down on the stand with the oil pan removed. The main bearing attaching the connecting rod of the #4 piston to the crankshaft had worn away to nothing. It had, as we later determined, worn the connecting rod and crankshaft journal so badly that both had to be replaced.  

Work stopped on the engine for a month or so, other than cleaning up all the parts, while I waited for the rebuild kit, crankshaft and connecting rod to arrive. I had ordered them from, a company based out of England where the engine was originally manufactured. Even with the shipping cost, the parts were less than from any US based distributor that I could find.

Once they arrived, I was able to send the engine block and head to a local machine shop to be cleaned, have the valve surfaces reground, and the cylinder liners replaced. I am pretty sure that this was the only boat engine the machinist, an old Vermonter wearing blue Dickies, had ever done. Nevertheless, he did the job at a decent price and even painted the block and head to boot. With the block and head returned, reassembly could begin.

Block on engine stand in Old Bill’s shop

It’s funny how taking something apart always seems to go a lot faster than putting it back together. Slowly, with constant reference to the photocopied black-and-white images of the engine manual, the pile of parts on the nearby workbench grew smaller and the engine took on a recognizable shape. Old Bill would come out every now and then to “inspect” the progress, offer advice and just chat. With so many bolts and bearings, special torques and clearances, my confidence that it would ever run again had hit rock bottom upon completion. 

Finally, I had it off the engine stand and onto the workshop table with IV tubes running to and from a small jug of diesel and the starter leads running to a tractor battery. The moment had arrived. After many thousands of miles and dollars and many nights and weekends of greasy hand and bruised knuckles, I hit the starter switch. When it fired to life, the look on Old Bill’s face was priceless, a look of pure surprise that must have mirrored my own. “I didn’t think it would go!” he later told me. “I knew it would all along” I lied.

On the workbench to test run

Take Two

The middle of May is not an ideal time when you are farming to sacrifice 10 days away. As nice as it was, the rates at Palm Cove Marina were well above our budget and the move to Green Cove Springs was worth it, even considering the travel. This time I was going solo and was able to “rough it” a little to cut costs. I took all of the rear seats out of our van and cut a piece of plywood to protect the floor. I placed the engine in the back on a pallet, leaving enough space to sleep for the one overnight stop on the twenty hour trip.

I made it to Jacksonville Beach on a Saturday night, had a day to rest up and prepare the boat and then had the engine lowered back into the boat on Monday morning. The install went well with only a few glitches including the come-along cable parting 6 inches above the engine mounts (that got the heart pumping!) and a broken temperature gauge. I had it running in its rightful place by that same evening.



Ready to be installed in bilge beneath cabin sole

The run to Green Cove Springs was great. I left on Wednesday evening to catch the incoming tide on the St. John’s River. Passing the Naval Station at Mayport with helicopters buzzing about, I entered the St. Johns River with its heavy commercial shipping traffic only to be immediately consumed by a thundershower the reduced visibility to less than 100 yards. Having no chart plotter or radar, I just steered a bearing that would keep me between the two banks and prayed that no monstrous metal bow would loom out of the showers ahead of me. I had never seen it rain so hard but it passed as quickly as it came and I was escorted into my anchorage a few miles further along in brilliant setting sunshine by several playful dolphins.


The next morning I again caught the incoming tide and passed through the city of Jacksonville. The river becomes quite narrow and the current the strongest at the city center which happens to be the location of the only two bridges that he to be opened to allow the boat’s 53 ft mast to pass beneath. In order to hold position while the bridge lifted, I had to turn and motor up into the current so as to not be swept into the bridge. At this moment my confidence in the engine rebuild was put to the full test. It was kind of funny motoring forward but going nowhere while looking up a busy Jacksonville boulevard at the many stop lights and pedestrians going about their business. After uneventfully passing through the city, I continued down the St. John’s which rapidly widened to several miles across. I was even able to sail the last ten miles to Green Cove Springs. A great ending to a successful trip.

In the travel lift at Green Cove Springs Marina
On the hard

The boat was hauled the following day. I prepared it as best I could to stay ventilated but dry over the Florida summer until our return in October. Rebuilding the engine was a big job, for sure, but in hindsight I think we made the right decision. I now have an intimate understanding of its inner workings, much more than I would have if we had continued to nurse it along. We probably did the entire rebuild for under $3,000 and now have an engine that will hopefully last for a very long time.

Returning to Vermont , I had to play catch-up on the farm but we are now rolling along in our final season. Everyone here is sad to see our farm business end and are constantly asking if we are excited to begin our new life aboard the boat. Honestly, the task of selling all the livestock and equipment, closing down the business and getting rid of nearly all of our personal possessions is a bit overwhelming. It is a big hill to climb before we can peer over the top to see what lies ahead. Yes, we are excited, when we have time to think about it, which is not very often.

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