This web page uses text scanned from the book "Hathor" by Larry Larkin published in 2013.


Although we started out with the noble goal of restoring this engine and using it in HATHOR because of its uniqueness and historical importance, at the end of the restoration there were a number of reasons that this was not feasible. This chapter is included only to document what we tried to do which may be of interest to others embarking on similar restorations, and to add a dimension of interest for all those who appreciate historic boats and engines.

This Lathrop engine is the last of its kind in many respects. No others of this model are known to exist. Within a few years of its manufacture, the Lathrop Engine Company, and every other company that made marine engines from scratch, went out of business, so it was one of the last pure marine engines made. After about 1950, boat engines became derivatives of automotive engines because the substantially lower cost of mass-produced automobile engine blocks dictated their use.


As I mentioned earlier, Peter Bates had purchased this engine, a Lathrop Engineers Model 115, because L. Francis Herreshoff, in his book "Common Sense of Yacht Design," recommended it as the finest marine engine built because every part was accessible and could be repaired in the boat while at sea. Unfortunately the engine did not live up to its billing. Contrary to Herreshoff's assertion that this was the finest marine engine made, it really wasn't. In fact it was a new, post-war design and it had not been perfected. I doubt they built more than a half-dozen of the engines and Lloyds Register from the 195O's does not show that any others exist.

Walter was a young man of 15 when the engine first arrived by railroad car in Williams Bay in 1948. Walter remembers being present when a crane lifted the engine off the railroad car and placed it on a farm wagon, and he and Peter Bates towed it over to the boathouse to install initially in DOREEN. In 1955, Peter decided to install it in HATHOR because he felt HATHOR was underpowered and would benefit from the power of this engine. Walter says he made 88 trips from his home in Elmhurst that year to install the engine, so he feels a personal affinity for it and a responsibility for its survival. Accordingly, he offered to underwrite the cost of its restoration.

There were two fundamental issues that negatively affected the operation of this engine. The first was a lack of lubrication for the valves. The valve stems, especially the exhaust valve stems. would rust from condensation and seize in the open position. In a book of remembrances written in 1950 by Edward Wells, a Lathrop field service technician, he recounts an instance where this model engine suffered from this exact problem. He felt the condensation was caused by the engine running too cold. This is probably a significant part of the problem, but-there was no oil supply to the valves guides, they depended on the lead additive in gasoline for lubrication and that was simply not enough. And today lead is not even in gasoline. When the valves seized it was necessary to remove the cylinder heads and pull the valves out with a puller. Then the valve stems were cleaned with emery cloth, lubricated, reinstalled, and the engine reassembled. This would take about 40 hours to do. and the engine would only be good for about 10 hours. Also, the temperature regulation had never been worked out. The temperature was controlled by a manual water valve that regulated the recirculation of the engine cooling water. The engine temperature depended on how far the valve was opened in relation to the speed and load on the engine and the temperature of the lake water. If the captain changed the engine speed, the engine would run too hot or too cold. So someone would have to go down into the engine room and re-adjust the valve by hand to bring the temperature back where it should be whenever the speed changed.

The second problem was that the reverse gear was very slow to engage and sometimes didn't engage. This was usually attributed to the shift mechanism or the skill of the driver, but as we disassembled the transmission and studied its operation, it became apparent the reverse mechanism had deteriorated and was badly worn.

But it was in the early 1960's when the real problem occurred. It was late fall. I was not present, but I was told later that it had been a struggle to get the boat out of the water and into the boathouse that year. Because it was late in the day and everyone was tired and hungry, Peter decided not to drain the water from the engine but to let it go until the following weekend. During the week, a sudden cold spell occurred which caused the cooling water still in the engine to freeze and crack all the water jackets. The following spring Peter took the engine apart and sent the cracked parts to a place in Minneapolis where the cracked parts were heated and welded with nickel welding rods. The engine ran for a while, but gradually over several years the welds cracked as the engine heated and cooled, and water leaks recurred. The engine was again dismantled and the parts sent to a place in Milwaukee that submerged them in epoxy resin and applied a vacuum to pull the resin into the cracks. Again it worked for a short time, but the leaks recurred. A few years later, when Bill Sills owned the boat, he also took the engine apart and tried to fix the leaks with various glues and resins, without enduring success. The final solution was to use roofing cement and wrap the cylinders with fiberglass tape. This was not particularly successful either. These cracks plagued the engine for the next 45 years.

We removed the Lathrop engine while HATHOR was still in the water because the engine weighed 3000 pounds and I didn't think we could easily get a lifting device inside the boathouse that would handle that weight. We used a barge that belonged to Reed's Pier Service to come along side the boat and lift the engine out. The crane set the engine on the beach where it promptly rolled on its side. Walter was standing nearby and said to me: "What are you going to do with the engine?" I said, "Walter. I'm going to give it to a museum." He asked: "Can it be fixed?" I said, "Anything can be fixed, but it would cost a lot of money to fix it. People have tried to fix the cracks for years and no one was successful. To make it reliable and durable you would have to make new patterns, make new castings, then machine them and fit them." I don't remember what was said next, but Walter subsequently took on the task of restoring the engine.

Unfortunately, everything we touched on that engine was broken. lt was absolutely amazing that it ran. Here is a partial list:

Generator: The ball bearings had rusted from lack of lubrication and had been ground to dust. The shaft had completely worn through the back bearing race and started to grind its way through the generator case until the rotating armature hit the fixed pole pieces inside and locked up. Then the key in the drive gear sheared off. Dave Hurkman, a skilled machinist, had to weld a new piece on the rear end of the shaft and re-machine it so it was back to its original size and would run true. Then he had to re-machine the bearing races and put in new ball bearings. The cooling fan had a cracked hub and had fallen off. That required a new center made and the fan machined to receive it. The magnetic poles and armature had to be rewound and the commutator turned down.

Reduction gear: When the reduction gear water jacket froze, pieces of the broken housing got caught in the gears and about 20% of the gear teeth on the pinion gear were broken. Ernie Styberg's company made a new pinion gear blank for us and his chief mechanic, Bob Radewan, re-worked the teeth on the internal-toothed ring gear to bring it back to true. We had to have a new gear cutter made because the gear was so old nobody had one anymore. The teeth on the new pinion gear were cut by Dean Engelhardt of Engelhardt Gear Co., a company located in Elk Grove Village that ' specialized in making unusual gears. We made new gears and shafts. We also replaced all the ball bearings and oil seals.

Transmission: The brass clutch plates were scored and warped because of overheating due to excessive shifting and slipping under load. The reverse band adjustment was completely used up so the transmission slipped when it was put in reverse. New brass clutch plates with an internal involute spline were cut out using an Electric Discharge Machining process. New steel discs were cut out of high carbon steel by Bertil Brunk. Then Styberg Engineering heated the plates red hot in a clamping fixture to relieve any stress with the clamping fixture keeping the plate flat. Then they were reheated and hardened to 40 Rockwell C, then ground to the proper surface finish by Bob Radewan of Emie Styberg's company. All the bearings were replaced. Two of the gears in the planetary unit had galled because lubrication holes had been plugged from metal debris and they were grinding their way into the carrier. Dave Hurkman, a marvelous machinist in Williams Bay, reground the gear ends and re-machined the carrier, inserting bronze washers to replace the lost metal. He commented that the transmission oil had so many metal particles in it that it was acting as an abrasive and the transmission was grinding itself to pieces.

Distributor: No centrifugal advance, the adjustment mechanism was rusted' solid. We were able to find a new old stock distributor from Jim Staib in McHenry. We bought a vintage Sun Distributor Machine on E-BAY to adjust the centrifugal advance weights and springs.

Magneto: No output. We hunted on the internet for a replacement and eventually went to Standard Magneto in Chicago to have it rebuilt. They also were able to build up a spare out of parts they had.

Carburetor: The throttle body was cracked on the rear carburetor from the throttle shaft up to the top mounting flange which leaked considerable air into the manifold. We had to buy three used carburetors, the last one from Jim Staib. an ACBS member in McHenry, before we had enough good parts to rebuild and make one good one. The chokes were not properly linked and didn't close.

Valves: We had new stainless steel valves made to eliminate any rusting, and new bronze valve guides cast and machined. Also hardened steel inserts were put in the cylinder blocks for the exhaust valve seats. We also had to design and build an oiling system to lubricate the valve stems, the earlier system depended on the lead in gasoline to lubricate the valves, a very unsatisfactory system. The oiling system we designed was unique - little oil tubes to each valve guide which was drilled to receive them - and was a real challenge to build.

Cam shaft: worm bearings that leaked excessive oil resulting in low oil pressure. We had new bronze bearings machined and installed.

Water pump: This was a piston pump with a packing gland seal around the piston like old-time propeller shafts had. The two valve chambers had burst from freezing. They were cast bronze and had been welded up but were still warped and dripped water. We replaced the piston pump with a rubber impeller pump.

Oil pump: Worn gears, shaft, -and housing produced inconsistent oil pressure. This possibly was a factor in the deterioration of the cam shaft bearings. New gears were made and the entire pump rebuilt by Dean Engelharclt of Engelhardt Gear Company.

Cooling system: All the water inlets in all the cylinder blocks had debris and zebra muscle shells in them and were partially blocked. A couple were completely blocked with zebra muscles and one had a piece of electrical tape wedged in and blocking it. Apparently the cooling water for the two blocked cylinders came in the reverse direction, the output from the other cylinders going into the exhaust manifold and some of it flowing back into the top of the blocked cylinders. When the water dripped in and hit the hot metal it turned to steam which accounted for the great clouds of steam coming out the exhaust. A closed cooling system has been designed with a new cooling water circulating pump and heat exchanger made by David Schodel of Sen- Dure.

Exhaust system: There was no plug in the drain hole in the bottom of the muffler so a constant stream of water and exhaust gas was entering the hull, depending on the battery driven bilge pump to empty the hull. Also the flange where the exhaust pipe attached to the engine had warped due to the stress of the long, heavy exhaust pipe hanging on it and hot exhaust gas ladened with unburned fuel and oil was spraying out on one side where the gasket had been blown out. This hot exhaust gas had further eroded the back end of the exhaust manifold so no seal was possible. We had to re- machine the rear end of the exhaust manifold and install new thread inserts to obtain a clean, true surface. A new stainless steel water cooled exhaust elbow was made by Miami Stainless.

Fuel Tank: As part of the McKee restoration, they installed a gasoline fuel tank because the former steam engine did not have anything like that. They used an 80 gallon heavy steel air compressor tank as a fuel tank. That seems to have worked all right until about twenty years ago when the fuel suppliers began to put alcohol in the fuel. The alcohol absorbed moisture from the air and, as a result, the inside of the tank was attacked by the alcohol/moisture combination and began to rust. This rust was manifested as a fine, talcum powder-like brown sediment that infiltrated everything along the way. It accumulated as thick muck in the bottom of the fuel tank that became re-suspended as clouds of silt in the fuel every time the boat rocked. This fine rust silt worked its way through the fuel filters and ended up as a thick layer of scum in the carburetors eventually plugging the jets. We replaced the fuel tank and entire fuel delivery system.

Starter: I don't think this was the original starter, it is a Delco and everything else on the engine was Autolite. The brushes were worn out. It appears that this starter was intended to go on the other side of an engine and to get it to fit in the opening on this engine the Bendix drive portion had been rotated 180 degrees from the motor portion to fit on the flywheel housing. As a result, two of the oil cups pointed down toward the floor and did not line up with bearings so they had never been oiled. We drilled new holes for the oil ' caps on the top. We were able to find new brushes and overhauled the starter.

As to the engine itself, I told Walter the only way we could use the engine was if the broken castings were replaced. I didn't think the old ones could be successfully welded given their history and also the fact that cast iron is notoriously difficult to weld.

We went on the internet to search for old Lathrop engines of the same model, we ran ads in the antique boat magazines, telephoned all the usual boat companies like Sierra Boat Company in Lake Tahoe and generally antique boat dealers throughout the US looking for that engine model and also for reverse gear and reduction gear parts. We contacted marine museums such as Mystic Seaport. They had a Lathrop diesel engine with the same transmission and reduction gear but declined to sell parts off it or to swap for our parts. They did agree to lend us a crank for use as a pattern.

To make new castings we had to start from scratch. Harold Coker, of the Coker tire company, helped us source patterns. This was a difficult job because seven cores were needed to form the valve chambers and water jacket. Harold was a true gentleman through all this and worked with us for -almost a year. We eventually went through four foundries before we found one that would and could successfully cast the replacement cylinder blocks. At that time I was still a member of an SAE Technical Standards Committee writing specifications and test methods for automotive parts, and I was able to obtain some leads from the people on the committee. From their suggestions, I found State Line Foundry in Rockford, owned by Steve Holdeman, who was willing to try.

I delivered everything to State Line in early January and met with their casting expert, a full bearded individual named Roger "Doozer" Allie who was complete with black casting sand sprinkled through his hair. We put the pattern and cores together and he thought he could make the castings but it would take about six weeks. We did one trial casting in February that we saw-cut open and found one thin area which they said they could correct. In late March they had eight castings made, so I went out to pick them up. I can't say enough good about these guys. They succeeded where others had not, they met their time commitment, the price was reasonable, and they were easy to work with. I took the castings to Ernie Styberg's company in Racine where, with Ernie's help, the castings were heat treated and stress relieved. Then I took them to a company near Sheboygan where the castings were submerged in a chamber filled with epoxy resin, the chamber then being evacuated so the resin would flow into any pores, and then the castings were baked to cure the resin.

The castings and engine were then delivered to Manitowoc Motor Machining. They took the engine completely apart. The cam shaft bearings were bad so new ones were machined and installed. New valve guides had to be made from scratch and were machined from bronze ingots, hardened valve seats were put in the exhaust valve passages and new stainless steel exhaust valves were machined. The exhaust manifold was trued up with new thread inserts put in the ends. Two of the six old cylinder heads had to be reworked. The engine was reassembled, except for the accessories such as starter, generator, ignition, cooling system.

The engine was painstakingly assembled during the next year. A pulley was added to drive the new water pump and another pulley on the flywheel to drive an auxiliary alternator for the general boat lighting, and also a pump for the hydraulic steering system.

The engine was started for the first time in April 2009 and ran well. Two issues arose that concerned me:

(1) As the engine was run up through various speeds, there were speeds where it ran smoothly and other speeds where it ran rough, so rough that it shook the concrete floor. Going back through all the engine components we found the crankshaft did not have any counter-balance weights. Apparently the designer felt the engine speed was too slow to warrant this feature, but I believe the absence of these weights was the cause of the roughness at certain speeds.
(2) The other concern was the reverse gear. The engagement was very gradual and slow. When the lever was moved to the reverse position, it took as much as five seconds for the engagement occur and it was tentative, not positive. There was also some drag in neutral. lt is possible that these issues could have been overcome with more time and analysis.

In October, 2009 we loaded the engine on a trailer and headed over to the boat house to put it back in the boat. Reed Construction company had their barge with the crane on it at the boat house to re-install the engine. The boat was partially backed into the water to provide space for the crane to work.

We attached the engine to the crane using a chain. The engine was lifted and the crane swung the engine around to insert it into the boat. At the crucial moment when the engine was half in and half out of the boat, the chain broke and the engine fell, hitting the side of the boat, and tumbling end over end into the water. I think the fact that the engine hit the soft lake . bottom saved it. We retrieved the engine, put it back on the trailer, and brought it back to my place. We took it completely apart again and checked everything. There was remarkably little damage, one carburetor was broken, the angle iron. that fastened the reduction gear to the engine was bent, and a few other minor things. Waukegan steel straightened the angle iron and machined the surfaces flat and true. There was some mud from the lake bottom on various parts so we carefully washed all the parts before reassembly.

In May of 2010, we started the engine again and it ran well, as well as before the plunge. But over the winter as I was reassembling the engine, I had time to reflect on two fundamental issues, the rough running at certain speeds and the slow engagement of the reverse gear. Principally because of these issues I decided not to put the engine back in the boat. It is a magnificent engine and antique boat people would have loved to see it run, but I felt I couldn't take the chance of an accident occurring because the reverse did not engage promptly and I didn't like the idea of the boat shaking at certain speeds. This was a difficult decision because of the time, effort, and money that was put into the restoration of the engine, but I felt it was the only choice.