Yanmar Safety Notice
- Thread starter Terry Cox
- Start date
I take it that Yanmar suggests a folding prop if sailors don't want it to spin while in the recommended neutral position. Doesn't a foldimg prop also eliminate the damage that the twisting prop would do when left in gear?
Yes . . . I don't have a Yanmar, rather a Universal. Until I got my MaxProp, I put the transmission in reverse. Now I put the tranny in reverse to feather the prop, then shift to neutral.
Agree, but the question seems to reappear with some regularity on this site, especially with NUBs.
THIS IS INCORRECT PROCEDURE. A MaxProp WILL NOT feather if stopped in reverse. You must stop the engine with the transmission engaged in forward for the blades to feather. MaxProp Instruction Manual.
Oh, I agree; just pointing out how long has Yanmar issued the advisory, but not well enough communicated as we continue to see the question year after year.
Gunni, I failed to state that I stop the engine with the transmission in neutral, then put the transmission in reverse to feather the prop.
I haven't tried stopping the engine with the tranny engaged in forward - may try that next season. When I read the instruction manual several years ago, I failed to note that MaxProp wants the engine stopped with the transmission engaged in forward.
@Gunni, the manual also states: "Modern transmissions are either mechanical or hydraulic. With a mechanical transmission, the best way to stop the shaft freewheeling is to engage the transmission in reverse (WARNING: engage the reverse only after the engine has stopped completely). With a hydraulic transmission you must shut off the engine while still engaged in forward. The remaining hydraulic pressure will in effect lock the shaft for a few moments, enough for the MAX PROP® to feather."
Based on this, both ways will work.
Based on this, both ways will work.
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If you stop a moving MaxProp'd boat drive in reverse the blades will not feather, and the shaft will not de-power until you restart the engine, power forward and shut down again. Transmission in forward brings an immediate power feather and stops shaft rotation; shut down from neutral brings a feather once shaft rotation stops, and if the prop stops turning. Continued shaft rotation is what the Yanmar Advisory is warning about. You have to stop shaft rotation as soon as the transmission stops operating or risk transmission wear.
Should have been more clear - shaft rotation from a MaxProp shut down in reverse and left in gear. The prop does not feather and will continue to generate torque - loading and wearing a hydraulic transmission. If you have a MaxProp and operate it properly it will not rotate when the engine is turned off.
So what is the issue with leaving a Yanmar in gear with a folding prop??? What bad things are alleged to happen, and what is the alternative?
The issue is the potential that the prop does not correctly fold and continues to rotate the shaft, loading the hydraulic clutch plates / cones - wearing them. You can check this by stopping in forward gear, shift to neutral and observe your shaft / transmission connection - if you see rotation you know the prop did not fold and de power.
Thanks Gunni:
I have the same response to this as another reader, which is that if you stop the engine while in gear, the prop WILL fold, and there is no way a folded prop will generate enough torque to rotate the shaft. Prove this to yourself by trying to rotate the shaft with the engine in gear, either underwater or while the boat is on the hard. Perhaps there is some concern about shifting gears while the engine is not running, otherwise this makes absolutely no sense to me.
I have the same response to this as another reader, which is that if you stop the engine while in gear, the prop WILL fold, and there is no way a folded prop will generate enough torque to rotate the shaft. Prove this to yourself by trying to rotate the shaft with the engine in gear, either underwater or while the boat is on the hard. Perhaps there is some concern about shifting gears while the engine is not running, otherwise this makes absolutely no sense to me.
Perhaps I should add that my boat has a 2 blade Gori folder. It takes an absolute minimum of backward water pressure to fold this prop, and since it is geared, both blades will always fold together. I should also mention that this prop, which is installed on a C&C 30 Mk 1, generates a good deal of vibration while underway under power, which was not true of a Gori 2-blade installed on a previous boat. The discussion related to shaft whip in another thread may have solved this problem for me. Given that there is nothing you can do to change the configuration of the propeller, I think the issue would be the placement of the Zinc anode. Any eccentric weight, such as an unbalanced anode, would drastically exaggerate any shaft whip. So I plan to change my anode to the lightest practical unit (doesn't erode much in fresh water), and also move it as close as possible to the cutlass bearing to keep the eccentricity to a minimum. Responses welcome.....
I have no experience with folding props, only feathering props and an improperly maintained feathering prop can and do fail to feather / depower. Something as simple as no grease, or improper grease, a bent blade, a wrapped prop. I assume there are conditions in which a folding prop would also fail to fold and continue to load the engaged hydraulic transmission clutches. It is a well known concern with Yanmar drive systems. That is why the voided warranty notice - keep the transmission in neutral.
Hi Gunni:
Thanks for this. Yes, I agree that folding and feathering props are very different animals, and we are likely talking about very different issues. As you know folder fold by rotating around a different axis than feathering props, and I suspect it takes considerably more torque relative to the propshaft to get them to engage/disengage. Especially with Goris, there is not much that would impede one of these from folding, unless you had a barnacle growing on the gears or something, and this is pretty easy to check and remedy. It is literally inconceivable to me that a folded Gori would generate enough torque to rotate the shaft of a Yanmar (mine is a 2QM15) while it is in gear. Of course a check would be to check the shaft while underway under sail with the engine off and in gear, rather than in neutral. Putting it in neutral seems counterproductive to me - this seems to me to want to encourage the prop to windmill.
Cheers,
Bruce.
Thanks for this. Yes, I agree that folding and feathering props are very different animals, and we are likely talking about very different issues. As you know folder fold by rotating around a different axis than feathering props, and I suspect it takes considerably more torque relative to the propshaft to get them to engage/disengage. Especially with Goris, there is not much that would impede one of these from folding, unless you had a barnacle growing on the gears or something, and this is pretty easy to check and remedy. It is literally inconceivable to me that a folded Gori would generate enough torque to rotate the shaft of a Yanmar (mine is a 2QM15) while it is in gear. Of course a check would be to check the shaft while underway under sail with the engine off and in gear, rather than in neutral. Putting it in neutral seems counterproductive to me - this seems to me to want to encourage the prop to windmill.
Cheers,
Bruce.