Can anyone please explain the following symptoms?
Motorsailing at normal power for several hours in light variable winds with a reasonably lumpy sea (sevearl swell patterns, some a couple of metres). Boat
speed all over the shop due to the confused seas.
is a Kanzaki
KM2P (cone clutch) on a Yanmar 2GM20
with fixed 3 blade
prop, composite bearing each end of shaft and a PSS seal.
Suddenly the prop / shaft / transmission
starts screeching in a high pitched fashion. Something like a dry wheel
bearing or such. Immediately pulled back to neutral and the noise
stops. Let it idle for a few minutes in neutral before gingerly engaging forward. All
sounded normal at low power
and then slowly advanced to normal power. Ran ok for say a minute or two before a terrible low pitch
rumbling grinding noise
occured. It sounded like metal being torn apart under rotation. This time, stopped engine
for a better investigation!
was normal in colour and quantity.
Shift lever was operating normally and with correct travel.
Found that in neutral, propshaft could be rotated by hand in either direction and felt normal.
No binding or noise.
In astern, prop shaft could be rotated by hand in normal direction and was locked in the other direction. This I believe is normal.
In ahead, prop shaft could be rotated by hand in either direction which lead me to think I have a transmission problem.
and coupling felt hot to touch not so hot as to burn, guessing about 40 - 45C. I don't know if this is normal or not!
Then tried rotating the engine
(decompressed) with hand crank and prop turned normally (ahead and astern) without any problems or noises. After that excerise, the prop could no longer be turned both ways by hand when selected to ahead. That is, it seemed normal.
Restarted engine and again tried ahead, this time, it seemed OK at low power
(1800 rpm), so proceeded for another hour to get to a safe(ish) fair weather
After a long look, we could not find anything wrong externally and tried the engine again. This time, all ran well at all power settings although I was not willing to try full power (3400+rpm) for more than a minute as we were a very long way from normal help (like people, phones, roads etc) and the coast had no safe all weather
Since then, we sailed back to safe anchorage (with coms) and used the engine for about an hour at low power and maybe 15- 20 minutes at normal power. No abnormal noises heard.
Still treating it very gently until we can get to a port with repair facilities (ie home
Any ideas as what might be the cause?
Prop shaft bearing???
Something fouling the prop???
I can't belive it has fixed itself