Hi all, first time poster long time reader.
We have just bought a
new boat (for us) with a
Yanmar 4jh4ae and
SD50 saildrive with a flexifold
3 blade 18inch
propeller. The combo has 550 hours on it. The last week it intermittently has not been engaging in forward drive. Sometimes it engages in both forward and reverse, other times only reverse, and forward only engages at high revs (with a clunk), or only partially engages, and other times it doesn't engage at all no matter what. I've dived on it several times, and on those occasions (n=2), when in forward with the prop spinning at idle, and revs are increased, the prop starts to increase speed but then slows down again almost immediately, despite the increased
engine revs. However, on occasion it will still provide full
power and drive the
boat forward at >6 knots as expected.
The Morse, linkages and
cables all appear to function well, and a
mechanic has just adjusted them thinking this could be the problem, however the fault is still there. The
engine,
gear box and
clutch makes no unusual noises. The prop seems to be properly fitted, not loose, and folding and functioning correctly.
I understand the cone clutches on these need regular re-lapping, but imagine if the
clutch was degraded this should result in almost complete loss of drive - which is not what we experience some times. I'm bamboozled!
I'm hoping to hear from the community whether these symptoms sound like the cone clutch, or possibly something else (the prop slipping on the shaft?)? All thoughts greatly appreciated, as we are currently cruising through the
Med on our way back to
New Zealand so don't have our usual
service people to call on, and
budget constraints require as much self-resolution as possible!
Cheers Tim
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