ZF Transmission Question

CSkipR,

I recently had my 2 ZF 350s replaced with ZF 360’s (one of 350s cracked it’s case, 350s no longer made) by Comachee Cove in St. Augustine. They did a good job on a difficult project. Also had a torsional coupler fail a couple of years ago. Comachee Cove I think still has my 2 silicon torsional couplers that are not very old and you may be able to save a couple of bucks by buying them used if they will fit. I paid approx $5000 for each silicon torsional coupler a couple of years ago. Also there may be a more durable alternative to the silicon ones available now. Tony Athens of Seaboard Marine would be able to steer you in the right direction and could also sell them to you as well. Good luck. Don’t wait to long to fix it as mine failed with no warning when we are offshore (of course). BTW I was a mile or south of New Smyrna when the case cracked and nobody in Daytona (except Sea Love) could haul an 18’ beam.

I'd want to consult the engine manufacturer before changing the type of coupler unless just switching to the silicon version instead of the black rubber in the same style. I used to think there wasn't any big difference until we were sea trialing our last small express. There was a strange knocking noise that seemed to be coming from the bell housing area but only audible in neutral at idle, bump up the idle or put in gear and it completely went away. The boat has 550 hp. QSB's and MGX-5065A's and neither Twin Disc nor Cummins suspected the black Vulcan couplings as they're basically just a rubber donut with no moving parts (when intact!). After weeks of detailed torsional analysis (always done on new installations anyway), no one seemed to have an explanation until one of the "old timers" suggested switching to a Centa dual stage coupling. A set was spec'd by Cummins and when swapped not only eliminated the noise but made a huge difference in smoothness across the board, no more clunk when engaging and no more chatter at low rpm's.

Here is a picture of mine that failed. Don’t want to hijack CSkipR’s thread but would love a brief description of torsional analysis and what it entails.

Hopefully K1W1 or one of our other engineers will chime in with more details. I know for all of our new builds and repowers I have to fill out a lengthy form detailing the entire driveline and it's installation, things like engine mounts size, spacing, materials and durometers of rubbers, shaft line sizing, couplings, bearings and spacing. Of course also specific engine and transmission types, reduction ratios, etc. I suspect most of it is intended to ensure everything is installed and sufficiently supported but vibration (harmonic) analysis is also part of it. CAT, MTU (Detroit) and Cummins all require this step prior to startup and have for as long as we've been doing it.

Control Masters in StAug. They are our ZF rep on these things.
Tell Ed I sent you.

On my boat they didn’t have to haul it to change the couplers. They turned the rudders and they slid the shaft back to gain the necessary clearance. Good luck. Of course it is your decision but if you feel comfortable spending the money I would replace both while you are at it. I have run into a number of people who have had this failure.

Not to that gasket. It's a heck of a job to get to that gasket, sliding the gear back is just half way there.