Hurth Transmission slippage Catalina 30

[Robsocks]

Hi, first year with our '84 Catalina 30 which was outfitted with a Universal MX25 and a Hurth transmission about 5 years ago. The transmission seems to be temperamental. sometimes it goes into forward, but increasing the engine RPM's has no effect on the propeller shaft. I gather this is slippage.
when i looked into the hurth's dipstick, it was overfilled with red transmission fluid, so I sucked it all out and put in a new amount up to the dipstick line. I'm hoping that fixes the problem, but have no idea whether extra fluid could be related.
..so am I in for a failure in the near future? and has anyone ever replaced a hurth with something else? I see PRM seems to be an option. I think I have limited space, so not sure I can get a bigger transmission in there. maybe there's other catalina 30 owners that can weigh-in.

Rob M.
Halifax, Canada
1984 Catalina 30 "albatross"

[Uncle Bob]

Originally Posted by Robsocks

Hi, first year with our '84 Catalina 30 which was outfitted with a Universal MX25 and a Hurth transmission about 5 years ago. The transmission seems to be temperamental. sometimes it goes into forward, but increasing the engine RPM's has no effect on the propeller shaft. I gather this is slippage.
when i looked into the hurth's dipstick, it was overfilled with red transmission fluid, so I sucked it all out and put in a new amount up to the dipstick line. I'm hoping that fixes the problem, but have no idea whether extra fluid could be related.
..so am I in for a failure in the near future? and has anyone ever replaced a hurth with something else? I see PRM seems to be an option. I think I have limited space, so not sure I can get a bigger transmission in there. maybe there's other catalina 30 owners that can weigh-in.

Rob M.
Halifax, Canada
1984 Catalina 30 "albatross"

Hi, not a catalina owner, mine is a Fisher 32 but had similar problems with the hurth in my boat. The cost of rebuilding it was only a little cheaper than a new PRM. The PRM fitted almost exactly, only a few mm longer and I fitted it myself, same spline and bolt pattern.
I'm happy with the result and supposedly have a much more robust box.
Cheers.

[Robsocks]

Thanks Uncle Bob,
so did you have to cut your propeller shaft, or is it just a few mm further aft now? it looks to me like there's a handful of alternatives for me if I don't have to use Hurth, but I'm concerned about creating other work.

[Uncle Bob]

Originally Posted by Robsocks

Thanks Uncle Bob,
so did you have to cut your propeller shaft, or is it just a few mm further aft now? it looks to me like there's a handful of alternatives for me if I don't have to use Hurth, but I'm concerned about creating other work.

The shaft is just a few mm further aft now, the only other change is the prm has the selector lever on the other side of the box to the hurth, a change to the single lever control so that the selection was not reversed and all was good.

[shakey doug]

HEAT, is the number one enemy of gearboxes over filing with oil is one of the major causes,due to slow heat dissipation You may be lucky enough to have gotten away with it, but if the plates have warped the problem is on going. Good Luck.

[Robsocks]

Thanks, so overfilling can cause heat?

[Sailmonkey]

TwinDisc/technodrive mg340/tmc40 should also drop straight in too.

And yes, too much oil can increase heat buildup but also can actually interfere with the clutch engagement.

When you changed the oil was it really dark and sparkly?


Sent from my iPhone using Cruisers Sailing Forum

[Robsocks]

Hi, the oil that came out was still distinctly red, but not see-through like the new stuff. it was dark.

[GRIT]

If the tranny lasted 25 years, why change brands? ZF has purchased the Hurth company, and make all the same transmissions Hurth did.

We've had a few hurth transmissions, and have put Hurth (ZF) in our new boat too.
The only thing I really dislike about ZF, is the transmission duty ratings. They have "pleasure duty" rated, light duty, medium duty and continuous duty ratings. These ratings basically justify manufacturers using transmissions that are underrated (and cheaper) for the engine hp. Which sometimes result in the "early retirement" of the transmission.

My advice, after replacing several "underrated" transmissions on our Corbin 39, is to stick with medium duty or continuous duty ratings, to get another 25 years of trouble free service.

Our new 50hp engines are using the hf 25, which is continuous duty rated for over 60hp. Transmission cost was $1500 US dollars from simplicity marine in Fla. You'll also find a few local suppliers, with similar pricing, once transportation costs are added.

Good luck, and if I can be of any assistance, since I'm in PEI, let me know.

Paul.

[Robsocks]

Thanks,
yes, I wonder about the pleasure craft duty. that seems like they're saying it's not strong. when I read about it though, it seemed that pleasure duty was enough for my boat, but from what I hear Catalina's have a hard time with these hurth transmissions, so I bet it has to do with the fact they're heavy boats and require a lot of throttle. seems like a duty upgrade makes sense.

[ex-12m-guy]

We had a similar problem with the same transmission on another brand of boat.

Turned out it was the shift linkage, not the transmission. The flex cable from the shift lever to the transmission was binding, and not allowing the gearbox to engage fully.

A new cable plus an overhaul of the shift lever mechanism solved the problem.

[darrelweb]

My Catalina is number 2601 and has the same setup you have.

I had the same problem. I replaced my shifter cable and replaced the clutch discs in the Hurth transmission. Cost me less than 300 US boat dollars, but I bought a manual on the transmission and a new set of clutches. I did the replacement myself, but you need to be a mechanical nut or know a transmission guy. I did not replace any bearings as all looked good and there was little play in the setup of the trust bearings.

The replacement to me was not hard....took a day to clean it up, fix it, and repaint it.

A side cooler on these transmissions work well and will extend the life.

I sail with my transmission in neutral. That is what the manual says and the transmission has two sets of thrust bearings on both sides of the main shaft. One set for pushing when running the engine, and one set for dragging the prop thru the water. The prop shaft spins when under sail.......

I have not had any problems with my transmission and I believe the clutch discs wore because the previous own was sailing with the transmission in gear. Causing premature wear.

Transmission replacement was not an option to me.....too many boat dollars and why change something that works......

darrel

[Jim Cate]

FWIW:

We had a sudden failure in the HW-100 tranny just after we bought this boat... clutches started slipping at anything over idle power. Did some internet research, and found lots of advice on these units. The main thing seemed to be that one needs to change the lube frequently, like at every engine oil change, and to be sure to use Dextron III grade ATF. We put in a new tranny (ZF10) and it has now some 3500 hours on it following that regime,and have had no problems. It only holds 375 mL of ATF, runs pretty hot, and I think the fluid looses its "good" quickly.

I don't know which model your tranny is... but I discovered (too late) that in our case, the next larger model, ZF12, was a drop-in replacement and cost little more. You might want to check that aspect out if you replace yours.

Cheers,

Jim

[Robsocks]

HI Darrellweb,
I consider myself generally capable, but pretty sure it'd take me 3x as long as a pro, so I'm going to spend the dough on a remanufactured unit unless someone convinces me that a new one or PRM /Twin Disc alternative make more sense.
what Jim says about the larger unit seems to make sense to me. I'm thinking I should go up a 'duty' level to make up for the fact that catalina 30's weigh about 3000lbs more than most 30' boats.

does anyone have any reason not to go up a level?

turns out my trans has about 366 hours on it. pretty frustrating to see it slip so soon, but I have serious doubts whether the oil was ever changed in it.

Rob

[highseas]

Buy the ZF10,use synthetic ATF.Keep in reverse when sailing,neutral also causes wear.The extra length of shaft shouldn't be a problem,mine wasn't.Try marinepartsexpress.