Yanmar 1GM10 is very long on the market and I believe it is still manufactured. It is relatively good and reliable, light-weigh, hard working one cylinder engine, delivering 9HP. It definitely requires often checks to make sure it will not fail, when really needed and in my opinion its price does not reflect on quality. I’m sure manufacturer is aware of its flows. But for some reason not much has changed in materials used in its making. Many of its parts are made of mild steel; the alu casting is fragile and it has to be handled with care. The water pump is known for its leaking and it doesn’t last long. However, it is very common on many small boats. Mainly for its simplicity, size and power delivered.

We were not very lucky with its purchase. It was second hand with unknown number of hours on the clock. The seller, claimed the engine was fully serviced and in good working order. When we went to see it, the seller demonstrated its running. It was smoking like an old locomotive and according to him, it was due to the remains of oil in the cylinders used to cleaning and compression test. Hard to believe as it looked like there was an issue. But at that time there were not many available and the price was still acceptable for the engine that started without problem.

The issue with it was … it has not been serviced at all for long. The oil was like a tar, thick and coal black; the breather clogged; impeller worn our; pump leaking; fuel filter clogged; the anode – non-existent; thermostat seized and valves out of measures. So, around £150 and few hours later I tried starting it again. It went like a clock-work with clean exhaust gases. It came without ref-counter, so I fitted it to know when the service is due. Now, it looked good for installation. (In the Engine Bedding, you can see it in its glory)

Happy sailing ever after? Yes, but not for long. After around 80-85 hours the engine begin to loose power and starting was not so easy anymore. One day it fail to start. The reason was a perforated cylinder head, irreparable.

It simply corroded to the point of collapse. While replacing it, I have examined the exhaust elbow, it was also perforated, causing corrosion of the cylinder head. The only sensible solution was to replace them both.
But, but, but … I mentioned some parts of this engine are made of mild steel and the elbow is one of them! I could easily get one at £185 and have it perforated some hours later again or find one made of stainless steel. Some replacement parts can be manufactured by Yanmar independent makers, so I found one and purchased it at £175. Unfortunately, the seller I used disappeared from the net. However, there should be others offering such products.
I would also recommend replacing if needed, the pipes around engine with those made of quality copper. Especially the one which runs under the water pump (yes, it is mild steel too). If you are not paying enough attention to your pump this pipe when corroded will make your engine loose all the oil. What a mess in the bilges?!? Not saying anything about possible damages to the engine itself and cost involved. Bare in mind, all the original parts and consumables are pretty expensive.

For the above reasons I usually get parts and the rest from Keypart.com. If you will not find some parts on their website, simply call them. But have part’s number handy. They are very helpful and friendly. By the way, parts catalogue is here.