C drive transmission failure

Roman Morozov

We changed Volvo engine to Yanmar 4JH4 -TE 2 years ago.  We have not changed the transmission. Recently the transmission broke, we suppose that this happened because we have not done maintenance for a long time.

1. We found a gear failure in the first part of the transmission.  Picture below. Can you please tell me if anyone had the same problem?

2. We also want to evaluate the condition of the transmission in the second part.  How can we do that?  If we need to open it, how to do it? Pictures below.

Roman and Ira Morozov SM2000 #320 Ginger

Olivier Beaute

Hello Roman and Ira,

this C-drive has been running without oil for a while!!!
You can get access to the inside of the lower unit if you take down the front plate (where you see the big pin that enters the GRP keelstub), bolted with ALLEN screws.
You will probably need to get in touch with AMEL in order to buy the gears and bearings, together with the prop shaft bushing and seals.
If you are in an area with good machine shops, they will probably be able to make these gears (although they are complicate as helicoïdal bevel gears).

Thank you for these pictures. This is a very good example of what not to do (neglect the service of the AMEL C-drive).

Good luck.


Jose Venegas

Roman and Ira,

The rust on all surfaces suggests that there was water on the transmission for a long time. In addition to making sure your lubricant level is OK, it is important to check that it does not look milky. Wearing of the third shaft seal near the propeller when the seals are oriented the “Amel way” causes water intake that mixes with the oil because the other two other seals are oriented to prevent oil loss but they allow water intake. If the seals are not replaced, and when the transmission is not used frequently, over time the water settles down and causes the corrosion of all surfaces visible on your pictures.

One good reason to keep an eye on the color of the lubricant, replacing the seals and thinking about seal orientation.

Jose Venegas
Ipanema SM2K 278

Craig Briggs

Roman & Ira,
If you go to Photos and Search for C-Drive you will get some pictures from when I pulled mine that may be helpful. In particular, you'll see how you have to cut away the fairing to get at the front plate allen screws. The entire removed shaft is also shown.
I learned only later that there is a lifting eye on the underside of the engine room overhead directly over the C-Drive that would have helped immensely to life it out.  Also notice the "O" rings on the "trumpet" - you'll want to replace those while you're at it and you should probably also renew the large hose that goes around the hull opening with the large hose clamps on it.
A super fun project - enjoy!
Craig Briggs - s/v Sangaris / SN68  Tropic Isle Harbor, FL

Roman Morozov

Thanks for your advice, Oliver! You are absolutely right, the neglect of the C drive service led to big problems

Roman Morozov

Jose, thank you for pointing that out. We definitely will follow your advice.

Roman and Ira Morozov SM2000 #320 Ginger

Roman Morozov

Thanks, Craig! We opened it today

Roman and Ira Morozov SM2000 #320 Ginger