I'm in the process of buying a 365 in Los Angeles. When I did the sea trial yesterday something happened that the two brokers on board couldn't explain. The clutch seemed to be slipping while underway. I noticed it while steering the boat out of the Marina Del Rey harbor channel, tacking under full main and engine running around 2000 rpm. When we would come about, in a 20 knot breeze, the boat would seem to lose a small bit of power though the engine didn't slow or rev up. Then in a minute or so it would normalize. I thought it might have something to do with the tacking but the broker said it did it earlier while underway without sails in the marina. I'm having an engine evaluation early next week but in the meantime I would appreciate any ideas about what might be going on. I don't know what trannie or v-drive the boat has, but they were allegedly rebuilt in 2009 when the new Yanmar engine was installed. It has 600 hours on it. Thanks, Johan.
There are several posts on this site about repowering with a Yanmar. Great motors that will run forever if operated within the continuous duty cycle curve, a true statement for any motor/ gearbox/boat combination. But repowering with a Yanmar on the 365 would not be my first choice.
Without repeating everything that's already been said regarding the Yanmar repower, it is essential to convert the Walter RV-10 V
drive to 1:1 (Stock is 2:1). A Yanmar 3JH (28hp) will not exceed the torque rating of the 1:1 V-drive, but it will come close. But V drives don't slip. They just get sloppy. (splines wear out ). Yanmar puts the gear reduction ahead of the clutch which is problematic from an engineering point of view because the tourque is increased by 2.36 (the gear reduction ratio). Pearson put it in the V-drive after the clutch for a good reason.
Yanmar does not build the gearbox. Its basically a Hurth HBW100 (KBW10) Yanmar does not publish the duty cycle rating on the gearboxes but Hurth does. With an HBW100 there is little or no margin for the continuous duty cycle rating mounted to the 3JH. I personally like to see 20-40% margin over continuous. Pushing an 18,000 lbs boat makes matters even worse for that little air cooled Hurth gearbox.
If you can determine that the clutch it is actually slipping by looking at the shaft into V-drive while under power, you will then need to repair the transmission for certain. While you have it removed look into getting a High Deflection damper plate from R&D Marine. This will smooth or reduce the tourque peaks from the 3 cylinder diesel and extend clutch life. Its tourque that kills clutches. But 600 hours on that Hurth gearbox is about right. I'd carry a spare gearbox with me.
Maybe you will luck out and find a Velvet Drive 71D (direct drive gearbox) in there and stock V-drive gearing. They don't burn out, at least not very often. What I would recommend for a fix if you're up to it. You will need a custom bell housing adapter ring.
I'm not trying to talk you out of this boat, it might be great value. They are all going to need work, and swapping out a gearbox sure beats for example fixing rotted deck coring.
Pete