Catalac 8M Diesel Engine Removal, Rebuild & Reinstall

One of my very few peeves about the Catalac 8M has to do with the inboard diesel engine placement. Apparently boat balance dictated the engine position in the boat. In actuality,  the Yanmar 1GM10s were placed so far forward in the engine compartments that the front of the engine is just 3 inches (75cm) from the rear bulkhead. The engines are almost literally mid engine mounted. Unfortunately, the Yanmar water pump, external oil lines, oil filter, thermostat ..etc..are all located on the front of the engine and are not easily accessible for normal maintenance. (Or I’m just too old to bend into a pretzel)

For years, I’ve been forced to figure out long, time consuming ways to perform normal maintenance on my diesels. It’s been frustrating to say the least. Finally, an overly warm engine and leaking oil lines in my starboard engine, were the catalyst for me to pull the engine and fix things properly.

As you can imagine, I struggled for some time with this decision. The removal of an engine from a sailboat is serious enough to send shudders down the spine of any prudent Captain. Furthermore, I hadn’t even worked on an engine since college days (many decades ago) until I bought Catalpa. However, the Yanmar website said my engine and transmission only weigh 97 kilos (about 200 lbs). I figured I could handle that. 

It’s interesting that I was able to locate and download the Yanmar Marine GM service Manual from one of the distributor web sites, however, it’s gone now. You can download the complete Yanmar GM service manual here. Yanmar Marine GM service Manual.

If you own a Yanmar diesel I suggest you down load the Yanmar engine service manual as it’s pretty handy to have around.

How to lift the engine out

My Yanmar diesels are accessed from my forward cockpit lockers. In pondering the engine removal, it was clear that I needed a hoist of some kind, attached to a cross beam to lift the engine up and out of the engine room. The actual lift out appeared to be straight up. I located an inexpensive hoist at a local hardware store for $44.00 (40 euros). After considering all options for a lifting point, I couldn’t figure any reason why my boom wouldn’t do. I dropped the boom into the cockpit and moved the topping lift to the lift out point on the boom, adding a shackle to attach the hoist. I then used the topping lift to raise the boom into the lifting position and two dock lines were attached at the boom end, which were tied off to rear cleats, in order to position a fixed lifting point directly over the engine. This made the boom rigid, (as in laterally unmoving) with the hoist positioned right where I wanted it.

With a lot of help from the Cape Dory posse in our marina, I managed to loosen the Yanmar starboard engine mounts. I then closed the cooling water seacock, shut off the fuel at the fuel tank, and removed all fuel lines, water lines and engine control cables from the 1GM10. 

As we began to lift the engine, there was a rather expensive surprise. Each of the 4 Yanmar engine mounts literally came apart during the hoisting of the engine off the engine bed. Fortunately, that was the one and only ‘lifting out’ issue as that inexpensive little hoist easily lifted the engine completely out of the engine space through the cockpit locker. I then loosened those docklines at the boom end, and swung the boom over my cockpit floor and gently lowered the engine onto a piece of plywood I placed there to protect the fiberglass. The operation was completed in less than 2 hours. So much for the horror stories of engine removal. On Catalac 8M’s this is as easy as rolling out of bed in the morning.

Engine Maintenance

I replaced the starboard water pump, as well as 2 external oil lines. A note of caution. These oil lines are two critical points that people must be aware(I learned the hard way). First, the hollow banjo bolts do stretch over time and have to be replaced. And second, the copper seal washers can’t always be reused. If someday you find yourself in my position, use new washers! I also replaced the oil filter bracket, oil filter, the high pressure injector fuel line, engine zinc, thermostat, and cleaned the injector housing of carbon.

Lastly, I cleaned the water cooling system using a household drain cleaner called ‘Snow-Bol’. I disconnected the water pump and then put an entire liter of this in the engine at the thermostat mounting and watched as over a 20 minute period, it bubbled out. I used a garden hose to wash away the chemical and debris that dribbled out of the engine and hit the cockpit floor. It was simply amazing how much black gunk came out of the engine water jacket. At the end of this operation I used the hose to flush the chemical out of the engine and was gratified to see amazing water flow through the engine block.

Putting it back where I found it

I bought 4 very expensive Yanmar replacement engine mounts ($100 each) and reversed the operation. The engine went back into the boat as easy as anyone could hope, leaving me with the task of alignment to the propeller shaft. This is probably the easiest engine alignment I’ve ever heard of. All 4 engine mounts were installed at their lowest adjustment setting and I discovered that the engine bed had been perfectly installed in the boat. There was perfect alignment vertically and just some minor lateral movement of the engine completed the alignment. The entire alignment procedure took less than 15 minutes. ( note: as these new engine mounts settle, alignment has to be revisited)

Now, for those of you who think this was error free, I feel it’s only fair to mention that those Yanmar engine mounts have different rubber hardness for front mounts than rear mounts. When I installed the engine, I put the stiffer mounts in the rear. I discovered 3 days later, that was wrong. I had put them in backward. Not only that, but the oil leak I repaired…. turned out not to be repaired after all. I had reused the sealing washers and bolts, which was also a mistake. The following weekend I got to pull the engine out of the boat again. Used the new parts for the oil lines and reversed the engine mounts. This time around the engine was on my cockpit floor in just 1 hour. I think if I have to do it again I can shave 15 minutes off my best time.

A slight oops

The starboard engine operation went so well that I repeated the process with the port engine. However, things didn’t go quite as I planned them. 

When I ran the engine on a test stand outside the boat, one of the engine problems would not go away. This engine was prone to generating clouds of black smoke at any throttle setting over 50% throttle. I had assumed this was a bad fuel issue, and was surprised when it kept on billowing smoke with new fuel with no load at all. 

I asked David Carter at Carter’s Marine Service to have a look, and after a few minutes of examining the engine, he explained that black smoke without any engine load  (the test stand) could only be one of two things. Either the injector pump was pushing too much fuel into the engine, or the compression in the cylinder was so poor that this fuel wasn’t being completely burnt. Considering the age of the engine, he surmised lack of compression was in fact my issue. He checked the engine compression and alas, his analysis was correct.

An Engine Rebuild

This situation was unexpected and gave me pause. A new engine is pretty expensive at $5500.00, if a person could locate one. Yanmar discontinued their 1 cylinder diesel marine engine. A rebuilt engine could be had for around $3500.00 (including freight), but rebuilt to who’s standard? I felt that purchasing a rebuild was too much of a risk, and yet a new engine was not an option. So, I asked David Carter to step in and do what he could for me with my sick port engine. 

David disassembled the engine, and had me take care of getting the cylinder honed and the valves reground (very reasonable at a local engine machine shop). He installed new rings, bearings, water pump, and anything else needed to restore the engine to pristine condition. In no time at all, my engine was purring like a kitten again. 

As you can imagine, the engine situation had suddenly become more expensive than planned and had to be run by the admiral. To control costs, I chose to reinstall the engine myself. I reinstalled this one after work on a Monday evening and completed the engine hookups the following Saturday. As with the starboard engine, the installation and alignment went smoothly and quickly, even with the new engine mounts.

In the end, this was the right decision. My rebuild costs were actually somewhat less than purchasing a rebuilt engine and my rebuild was done by a diesel mechanic who has 30 years experience. More importantly, he’s someone I trust completely. If anyone reading this web page has a boat in central Florida, and requires their diesel serviced, I would highly recommend David Carter at Carter’s Marine Service.

Meet my new Starboard Engine

Not that many years after rebuilding the Port engine, unsurprisingly, it was time to apply all this new 

Rick installing new starboard engine

found knowledge to my starboard engine (2016). Once again, the engine was hauled and brought to David Carter, however I wasn’t as fortunate this time around, as the engine had no compression at all. When disassembled, it was determined that both the engine block and the engine head were severly worn. I had to order both from Yanmar as well as many, many assorted parts. 

I thought a better option was to just replace the engine, however if you recall we discovered that Yanmar no longer builds the 1GM10 engine series, and finding another brand of engine to fit the space was a problem. Most importantly, I wanted two of the same dang engines in my boat! 

What made things even more interesting is Yanmar had no engine blocks for the their 1GM10 anywhere in North America. In the end, my new engine block was ordered from Yanmar Japan and took 6 weeks to arrive (proverbial slow boat). The new engine head was available through the Yanmar distribution chain. Replacing both the block, and the head in essence means the starboard engine is in fact a new engine, built from the block on up with new parts and in the end, cost as much as a new 1GM10 would (if they still built them).

S/V Catalpa now has two new engines and is running in top form with clean bilges once again.


By Rick

Owner of a Catalac 8M and Catamaransite webmaster.

Leave a Reply

Your email address will not be published. Required fields are marked *