Messages

Bob - I'd like to think you could identify whether or not the tranny is slipping while under load with your hand-held tach by knowing the gear ratio.  I haven't done this but, I can't imagine why this wouldn't be accurate.

On the Hurth / ZF transmissions the gear ratio is shown on a label attached to the top of the tranny near the shift lever.  If its a hurth HBW50 or ZF 5 its probably labeled as 2.05.  According to the manual I have, the "A Ratio" is either 2.045 or 2.722 on a ZF 5 M.  If the label shows "A=2.05" on your tranny, multiply the shaft RPM by 2.045 while in forward under load. This should be the rpm of the engine assuming the connection between the tranny and shaft is good.  If so, the tranny isn't slipping and your problem is not the engine or tranny.

After that, the following guesses come to mind.  Is anything causing the prop to be less efficient than it was when you first re-mounted it after the prop pitch change?  Did it become bent, is there slop in the cutlass bearing or strut, is the key in the prop doing its job or does the prop slip while under load?

MarcZ - Yes, I too would like to participate in fleet activities when I move my boat to the upper Chesapeake in the spring!

BTW, I know the hard way that the engine is capable of running faster.  I made a minor cable adjustment to get my RPM up from 2,900 to 3,000 @ full throttle.  The following weekend, after getting a photo tach, I checked it and learned my cockpit tach was off.  At full throttle the engine was actually running slightly over 3,100.   So, I "fixed" my cable adjustment.  Yeah, I know, a smarter person would've checked first...  Fortunately, I've almost never run near full throttle and was only testing after knowing the engine was a full operating temp. Now I know I need to calibrate my cockpit tach.

I'm wondering what engine you have.  The top speed that I've seen published by the MFG for any M25 is 3,000. 

Your absolutely correct.  I think Stu was considering that a bad damper plate might be a cause for the feeling that the tranny isn't engaging in to fwd as firmly as in rev.  Nobody wants it to be a bad tranny

Paul  -Thank you. Another member sent me an email with Dan's contact info a short while ago and I sent an email asking about the tranny. He also provided a phone number however, I figured to go the email route first.

Thanks Stu.  I found that as well and enjoyed the site but, didn't find any contact information for him.

Thanks Paul.  I looked but wasn't able to find that member.  Any suggestgions?

Ken, thanks for checking!  Can't complain about $100 over dealer cost.

Ken, I think the price was good for either however, it wasn't specified in the email.  I think the 407205 is for the A POS 2.136 fwd gear ratio and the 407206 is for the 2.632 forward gear ratio.  I need gear ratio 2.136.

Stu - Thanks for the link.  I'll try and see what I can glean from your search suggestion.  Fluid change and final fill was to the recommended level for operation only.  I didin't think to fill to level for extended storage.  I only plan on being on the hard for 6 months ad they suggest 1 year plus for filling to the top.  I hope to have the tranny issue resolved before I commission her.

Craig - I shifted at the tranny and the lever was significantly farther than the 30 degrees, if I recall from the manual correctly, is needed.  I also had the Admiral confirm the shift lever on the pedestal had clearance.

Ken - Thanks!  I'll try calling them.  I got a price for a new ZF12 for $1,525 from someone in NJ and a rebuild of the 5 for nearly $1,500 because the OEM parts are really expensive now so, it's a no-brainer to go with new and one that is beefier.  I think the 12 price is really pretty good.   I haven't gotten serious about the Damper Plate yet but now starting to research that replacement as well.   I just don't see any value in not replacing it when I do the tranny work.

Also seriously thinking about a tranny cooler since one can be added to a 10 or 12.  Any suggestions?  I'm not even sure where you connect for cooling.  The heat exchanger?

Thanks for the links regarding damper plate replacement guys.  Lots of good infiormation and I'm now hopeful that my low RPM vibrations may be reduced after damper plate replacement but, I don't expect that to help with the slipping/engagement in to fwd problem.

I had assumed that I'd need to remove the bell housing to replace the damper plate but, now hoping I might be able to get it out after tranny and tranny mount adapter plate are removed from the bell housing on the 25xpb.

I've read some concerns over the R&D damper plate durabilty vs the Sachs but I don't recall any mention that the design was different.  Assuming there's an option to go with a high deflection R&D on a 25xpb, does anyone have any experience with this?

Also, any thoughts from anyone regarding the ZF10 vs the ZF12 as a replacement for my ZF5?   I know the gear ratio difference between 2.14 (zf12) vs 2.045 (zf10) which is nearly identical to 2.05 (zf5) so, zf12 will reduce my speed prop RPM by about 50 @ 2,500 engine RPM as compared to my zf5.  I'm assuming that reduction in SOG while cruising will not be noticable.

Stu,
Thanks for the feeback.  An observation I made, but neglected to include earlier, indicates the tranny slips when put in to fwd.  I carefully watched the shaft while shifting between fwd & rev after I changed the fluid twice.   I was able to see, several times when shifting in to fwd, the shaft rpm would increase after a few seconds.  I would expect it to turn a constant speed immediately after shiftng in to fwd as it appears to when shifting in to rev.   It wasn't drastic but, definately notcable.  If it can be seen with the naked eye, I'm sure it would be significant with a tach.  So, I think this is an indicator that the clutch plates and or thrust bearing(s) are severly worn.  After what I've read about the 5M not being very durable if not well cared for, this would be no surprise if neglected like mine appears to have been.

I welcome your or others thoughts if there's some holes in my logic knowing I'm not a mechanic by trade and new to this.  I'm surely not trying talk myself in to a new tranny.  I'd much rather put that money elsewhere on her.

That been said, I'll read through what I can find on the 36 site on the Damper Plate since I plan on replacing mine.

So... my, new to me last Spring, 1987 34 appears to need the transmission "fixed" and I would like the opinion from those that know more about this than I do which, probably includes everyone that's a member of this great org...  I say that because this is my first boat since I sold my 16' Hobie 30+ years ago so, I have much to learn.  I've sailed occassionally with others and been on a 2 week cruise on a Gulfstar 52 in the Abacos 25 years ago and a 2 week cruise in the Virgin Islands on a Hunter 42 15 years ago so, the love of sailing has always been there.  Just needed the time and resources to get one of my own.

Following paragraph is the lengthy background.  To get to the question, skip to the next paragraph 

The boat was re-powered 10 years ago by a PO with a M25XPB / ZF5M transmission.  I bought it with 450 hours on it.  Yes, had it inspected and nothing reported about the tranny.  Not having any previous experience as an owner/skipper, I didn't notice that the "feel" when shifting in to fwd was different than rev. Kind of slide in to fwd, firm engagement when going to rev.  That came to mind when I wondered why it didn't begin to move fwd when I shifted to fwd after backing out of my slip mid-season a couple times.  I began to do some research and looking and I believe the tranny is toast or nearly toast or the following reasons.  A big oversight on my part was not checking tranny fluid right after buying.   I did the oil, fuel filters and everything I could think of for the engine but neglected the tranny.  Well, when I checked, no evidence that the fluid had ever been changed.  Factory paint undisturbed.  Checked dip stick and no fluid.  Drained and found thick burnt fluid to no surprise.   I filled with new fluid, ran to get to get it warm, shifted a few times then changed again.  Tranny shifts a little better but, I don't think I can trust it.  I'm open opinions on this.

So, my research shows it'll be little savings to rebuild the ZF5 and likely far better to go with a brand new ZF10M, if I can get one since they are recently discontinued, or go with a ZF12M.  I'm not going by the inflated price for the 10 on CatalinaDirect.  I'm inclined to go with a 12 but the ratio gives me pause.  Going from 2.05 to 2.14.  Am I making much ado about nothing?  BTW, I'm aware the 10 is about an inch longer than the 5 and the 12 about 1-1/2 inches longer than the 5 so, I'm assuming I should probably have the shaft shortened to accomodate either instead of asking more of the Cutlass bearing which also must be replaced while the boat is on the hard for the winter.


Thanks in advance to everyone for your input on this and for all the great info I've obatined from this group!!!

-Bill

Congrats!  My wife and I just completed our first season on our new to us 87' #333.  Like you, I've been reading the hell out of this site and everything I can get my hands on.  Other than enthusiasm and love for our 34, I haven't felt I've yet had much to offer this site.  So, to you I pass my enthusiasm and hope that you get as much joy from your boat as we have from our "Beginnings".  Ours also needs a bunch of TLC and I'm up for the labor of love.  This is our first boat, other than the Hobie 16 I bought new in '82 and sold in '85.  Whew, so,so much to learn!