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Post by georgia on Jun 24, 2019 1:42:49 GMT
Interestingly. I backed out of a slip with a 39i and it simply wouldn't go into forward. luckily I was able to back into an empty slip and tie her down. wiggled the transmission a bit and finally got it into forward. so I drove it back to its home and took a look. Did the appropriate troubleshooting and determined the transmission had failed so we ordered a new one. It arrived. So we pulled our yanmar 3jh4e transmission on the 39i. straight forward. bolts on the engine and bolts on the propshaft. dropped the new transmission in and reconnected. the bolts connecting the transmission to the propshaft were different sizes so i'm assuming it had been replaced previously... I purchased 4 high quality bolts, nuts, and lock washers... put them in, locked them down, and after an 12 hour day of motoring/docking etc (lots of transmission and engine use) the 4 bolts came loose and literally fell out.... Luckily we caught it at the slip and tightened them again.
Question: why would these bolts back out and fail like that. they were seriously tightened by two seperate people. Lock washers were used... we've since replaced the nuts with lock nuts.... but WTF ?
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Post by heatherina on Jun 24, 2019 8:56:14 GMT
You could also put some Loctite threadlocker on the threads. Also it may help to fit a fine thread nut and bolt. Always use a torque wrench so that you have even force on each but and bolt.
Hope that helps.
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Post by georgia on Jun 24, 2019 16:00:39 GMT
hmm... torque wrench.... there are lots of ways to make them fast... but I want to know reasons why they world work their way out.
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Post by heatherina on Jun 24, 2019 16:12:20 GMT
Vibration - misalignment, imbalance ( propeller), weak engine mounts.
Hope this helps
Ian
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Post by heatherina on Jun 24, 2019 16:17:53 GMT
Also your propeller shaft bearing (cutlass) could be out of tolerance.
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Post by georgia on Jun 24, 2019 16:28:55 GMT
yeah... those are the things i've been considering. luckily not my 39i... it's a friends. we've been pondering this for a couple days now.
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Post by johannes on Jun 25, 2019 9:43:07 GMT
Sufficient vibration will work any nut loose, no matter if you use Loctite, locking washers, nyloc etc. The only thing that works for really high vibration environments is this, used by NASA and in Formula 1 cars:
But shaft bolts should normally not require such exotic measures.
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Post by lennies on Jun 25, 2019 15:06:48 GMT
thinking about what you wrote, "the bolts connecting the transmission to the propshaft were different sizes so i'm assuming it had been replaced previously
" it strikes me that this bolt problem may have occurred sometime in the past. Whatever made them need to be replaced the first time is still with you.
I would suggest a proper look at engine alignment as that is such a frequent malady. It doesn't take much misalignment to set up a vibration in the drivetrain which will loosen fasteners. Remember, you can't see the vibration and probably couldn't feel it either, but it misalignment can be measured and repaired.
If alignment is good, check the prop shaft fit in the strut bearing. Sloppy fit there will also induce a vibration giving the same results.
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Post by adelio on May 4, 2023 21:05:47 GMT
Hi, was it difficult to take the transmission out of the engine compartment? You had to remove some parts around the engine to extract the transmission from te engine vane? Do you have a 3 cabins version or 2 cabins? I should remove my transmission too and I'm glad to have some hints. Thanks!
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