Seized Transmission - Universal 24hp M-30

[Anteris]

Good day! we are a new member, new boat owners and excited to be a part of Cruiser Forums. My gf and I recently purchased a 1982 Cape Dory 33. We have a 24hp Universal diesel engine (M-30) that was rebuilt in 2016 (246hrs). Between the survey, a day trip and then a 45nm motor sail from Stuart to Sebastian inlet, we have had great engine performance (totaling approx. 80nm). However, after motor sailing to Sebastian Inlet, our transmission seized.

As we were approaching our anchorage I attempted to shift from forward to neutral when the throttle seized and the engine secured. We safely anchored and started to troubleshoot.

We found that the transmission lever (on outside of transmission) is limited in motion. Further, the shaft is locked. We have isolated to a point where we are confident our issue resides inside the transmission.

Anyone have any insight on experiencing a similar issue? Are we overlooking something simple?

For now, we plan to drain the oil to check for debris/shavings, check the clutch, look at price differences for rebuild or replace (if necessary).

Thanks for any help! Hope everyone is healthy & well.

-Austin & Mara

[Lepke]

I assume you removed the transmission cable and tried to shift the trans? With the throttle and trans cables disconnected can you verify the cables have full movement.
Can you get the trans in neutral? Then turn the shaft by hand? Can you start the engine? Does the throttle lever move freely?
Odd that the engine and trans died at the same time.

[moctrams]

Go to Capedory.org and ask your question. The folks there are very helpful and could put you in touch with a mechanic in your area.

[Anteris]

Lepke: we removed the cable which then had full range of motion. Crawled into engine space and played with the transmission lever which had limited range of motion and wouldn't budge past a certain point. Cannot get the trans back to neutral and cannot get the shaft to turn by hand, pipe wrench, or vice grip (even got in the water to try and turn the prop...no luck). Engine will not start (but we are certain that is because it is stuck in gear). *scratches head*

moctrams: Will do! Thanks for the pointer.

Thank you both! Hope all is well!

-Austin & Mara

[a64pilot]

Being stuck in gear won’t stop it from starting, but a seized transmission certainly could.
Of course it could be the flex plate, but to find out about that your still pulling the transmission. Can’t hurt to drain the oil, but I wouldn't spend a whole lot of time trouble shooting myself, I’d pull it.
Most often things can be fixed for less money than replaced just as a general rule.

[billknny]

Do you know the make/model of the transmission?

We had a simple rear seal fail on a ZF25M after ~10,000 hours. Simple... yes... except to replace it the entire unit has to be completely disassembled. We were quoted $1600 (16 hours) of mechanics time to rebuilt the unit, PLUS whatever parts were needed.

A factory new unit was $2100. For us, that was an easy choice.

[Michael Carroll]

I have the same motor/trans.
More than once I have solved (maybe the same problem) by:
Disconnecting the shift cable.
Removing the shift actuator cover (4 bolts).
See if you can shift it using a slotted screwdriver in the vertical slot, sliding it fore and aft.
If no you may find what is jamming it.
If yes reassemble making sure the ball of the actuator aligns in the slot.
Sometimes the actuator ball jumps the slot and jams.
Readjust the shift lever.
Good luck.

[FPNC]

It will be cheaper and easier in the long run to replace with a new gear. The new ZF small mechanical gears are not the most reliable but they are the most expensive. Use a small PRM or TwinDisc/Technodrive mechanical gear.

[Suijin]

The general consensus with ZF transmissions is replace vs rebuild. Reason is that they are never "as good as new" after the rebuild and so the small premium of replacing with new is worth it.

I went through the same evaluation with my ZF vee drive. And my issue was just a leaking seal.

[Anteris]

Thanks everyone! We are headed back down to the boat for the weekend to trouble shoot. We have a specialist coming out to confirm diagnosis/give some pointers. Worst case, we haul her out and replace...excited to see what we can learn!

Will follow up when we get more info/repair.

Hope everyone is healthy & well!

-Austin & Mara