I have had my Yanmar 1 GM from about 1985. Purchased at a bargain price
(new) of $1400 AUD in Darwin when a business was closing down. I sold the Kanzaki gearbox
for $1800 and then bolted a lay shaft onto the flywheel. The shaft ran a freezer compressor
, an A/C compressor
, a diving
compressor and a water pump.(all with clutches except for the water pump) I also attached an extra pulley to the front and then hung a 5.5KVA 240 VAC alternator underneath. No, I did not run all at the same time! This little engine was going to earn its keep.
The small built in water pump was “removed” as the impellers didn’t last for long and were expensive. The 1 inch pump provided the raw water cooling
for both the engine and the condensers for the freezer
Being a propulsion
engine, the voltage regulation for the alternator is nonexistent. The alternator runs electric
jugs, power tools etc. Manual (throttle) regulation is required to run a microwave oven
. I could not locate a “bolt on” regulator
This has been in place since installation
. For ten years it was run for about 8 hours every day. Since then, the yacht has been in marinas
so little use was required.
The big grace with this engine is that being direct salt water
cooled, it does not require a heat exchanger
My engine has shown no corrosion
problems in the casting or cooling
gallery of the head
Issues. Maintain it carefully. Oil, filters air cleaner and the zinc electrode. (buy all in bulk but not from Yanmar.. too expensive). Use a quality primary filter and preferably an overhead fuel tank
bleeding is a pain as it must be done at every fitting. I have installed a bleeder fitting on the top of the secondary (small) filter. (It is a refrigeration
type bleeder. Cheap)
The alternator is a Mitsubishi model. You may consider replacing it with a larger one if space is available. The starter motor is also available from other suppliers. I have replaced both recently.
An issue here is: - the B+ terminal is the regulated output. It should be connected back into regulator
with a short wire. Removal
causes the output to lift
from 14.26 Volts to 15.24 Volts which is too high. If not sure, ask someone who does.
The original lift
pump can have a short life with the little valves failing. Try to keep a spare, or parts
However, the worst problem was the copper exhaust
manifold. It will corrode inside (not observable) and then leave salt
spray on the very small exhaust
hole on the head
. This will ultimately shrink the exhaust hole and corrode the head. Due to the internal copper bent pipe, repairing the exhaust is very difficult.
The Yanmar exhaust replacement price
will shock you so do consider having a SS one made from off the shelf parts (threaded). Also, the exhaust has three mounting studs. If possible, tap a fourth threaded hole into the head and use a more substantive four hole exhaust manifold flange. The copper one distorts too easily and can leak.
Some other owners have mentioned corrosion
of an oil line that passes under the engine. Keep an eye on it!
The key switch on the panel is given to breaking where it goes through the panel. Look out for a more robust alternative. I have repaired mine a few times with super glue.
I have also added a manual valve and drain hose at the sump to allow for complete oil draining as the plug
is not easily accessible for my installation
I made my own exhaust muffler
using 150 mm PVC vertical pipe 60 cm high. The wet exhaust enters via a flexible rubber exhaust hose at the top and goes down an internal 50 mm perforated pipe. The outlet is at the top and consists of a 50 mm internal pipe that reaches down to about 10 cm off the bottom. The hull
outlet is over a meter above the load water line at the transom, thus reducing heeling issues (water ingress). The cylinder base also has a drain with a manual valve. All plastic. Clearly there are variations of this mode, but it has the important “non return” effect. You can hardly hear the engine running.
I have had no experience with the oil pump issue mentioned. Maybe I am due for it!
Being a single
cylinder engine it can leap around a bit. Flexible mounts are essential. Over all though, a good little engine that keeps on working. Just avoid anything with a Yanmar sticker on it.