I replaced my transmission last year. I bought a Tmc 40 from Joe DeMers at
Sound Marine Diesel. He used to rebuild the hurts, but stopped because in his opinion it is a poor design.
According to Joe;
The TMC 40 is a much better gear, because of the below reasons.
1] simple cone clutch construction. [ he Hurth uses a multi disc type clutch, more complicated, more expensive, and unreliable]
2] Overbuilt for 20 hp [ this gear is standard on our 30hp engine ]
3] direct replacement of the Hurth [ just bolt it on ]
4] 1 year warranty when buying a new gear [ Hurth /ZF is known for making any warranty claims a BIG HASSLE]
5] much less $ than a Hurth / ZF gear
So far I have been happy with new tranny.
Some other things to consider if you go this route.
Replace the damper plate, on my boat it was made by SACHS. It has 6 springs, a 5 bolt pattern and 10 tooth spine. The diameter is 6-3/16" to the OD. The bolt circle is ~5 5/8”.
Part number on the damper plate is 1866 061 001. Joe had a replacement.
The shift linkage moved from starboard to port, so you will need a different mounting bracket for the linkage. Joe also had this.
If I recall, this tranny is about 1/4" longer. So your shaft will slide back slightly.
Last, it is a tight fit. I had to jack engine all the way up to make room sliding out the old and installing the new.
All in all, it was only about a two hour job. Good luck.