Hello, we have a Freedom 33 cat sloop and have just gone through our 2nd gearbox (Italian made - Technodrive) and Perkins Perama engine in 3 years. Last gear box was brand new 2 summers and not a lot of mileage ago. The boat is 21 yrs old, but we have had it 5 years. We appear to have had excessive wear on the clutch cone. Forward gear stopped engaging when selected, though reverse luckily got us out of trouble when things became exciting last month! Has anyone else had any similar problems with gear boxes? We were wondering if the distance from the engine to prop (from under the galley sink, rather than the companionway) causes any problems?
Although the new gearbox clutch cone is in and replaced now, but we dont think it has fixed the cause so any ideas appreciated? There doesnt appear to be any untoward vibration on the prop shaft and nothing is moving that shouldnt be - we dont think!
many thanks… Emma
Hi Emma,
setting aside the possibility of faulty manufacture, the two main causes of premature failure of the gear box are misalignment and torsional vibration. I would examine the installation looking at the following. Is the engine on resilient mounts or hard mounted . What is the distance from the gearbox flange to the first propeller shaft bearing. Is there a flexible coupling between the gearbox flange and prop shaft coupling. Is there a thrust bearing on the prop shaft or is the thrust taken on the gearbox. What is the reduction of the gear box and what is the rated power of the engine. How heavy is the shaft and propeller - this can be a factor where the shaft is long as there is more inertia in the drive train meaning you get a decent sort of a clonk when you engage the gear. Has the shaft alignment been carefully checked. Once I had considered all of these factors there might be an indication as to which area could require attention or modification.
A year or two ago I had a Herreshoff H28 in which I had installed a new diesel (13hp) with Technodrive gear-box. The engine had a dreadful vibration and we tried all sorts of cures eventually settling on very soft mounts and flexible coupling. However, we had not fxed the problem, only shifted it to, you guessed it, the gear box, which failed with a loud bang at the worst possible moment. In the end the engine was found to have an unbalanced flywheel which it was accepted caused the vibration and the gear box failure. The engine and box were replaced and no further problems. I had two other engines, 20hp and 42hp with Technodrive gears and never had any problems with them.
Regards,
Hi Mike,
I had to share your post with an engineer friend of ours who helped us sort the problem in the end. Since he hasnt commented on your questions, I can only assume that our engine is mounted fine (hard mounted) and that all the bearings, distances etc are OK. (I am not an engineer at all, but learning basics fast!)
We don’t think misalignment is the problem and there is no excessive vibration when in drive. Since I first posted this, we have been told its the cones inside the gear box that have worn out. That gear box was put in 2 years ago, but am now wondering if it was reconditioned as we didnt see the final receipt although we asked for it. The cones basically went from gripping to slipping in about 18 months.
We had changed the oil regularly as instructed, but now think there could be a possible gear box oil problem. The gear seemed to go in fine(ish) when warm, but when cold, not at all. That points to the fact that when the oil is cold and thick it remains as a layer between the cone faces. As it warms up, the cones are able to force the oil out of the way and get a friction material to steel grip. The oil used is ATF so in theory its the correct one. We havent changed it from ATF, but if any oil expert knows more let us know a different type to try? Note though, we did wait for the oil to warm up before casting off and of course tried the gears as well. Unfortunately I couldnt take the mooring line off the buoy with it in gear, so we had to put it back into neutal. When it finally went into gear (just before hitting the next boat) , it seemed OK(ish).
I think the only thing we can do is see what happens in another year or so. We will however watch out for any increasing engine vibration. I am heartened by the fact your techno drive gear boxes have in general been good and reliable. We have been able to just replace the cones this time, but if the gear box goes - its £700 so not something you want to do too often!
Thanks again for your help.
Emma
Emma;
I’m a newbe so I hope you’ve figured out your gearbox by now. We had the same problem and it was because I wasn’t putting the engine in reverse when we were sailing. A “stupid” thing to do, but I’ve been sailing a long time and didn’t realize that on most tranny’s that’s what you have to do. The freewheeling wore out the clutch.
Carl
Good point Carl, I had forgotten about that one and it seems a very likely possibility. My Hurth is OK to free wheel but it is quite possible the technodrive should be locked in reverse - not ahead, when sailing. frequent oil changes are mentioned, If the oil was in any way discoloured, (wear particles from the clutches) that would tend to support this point.
Regards