Adding a Transmission Cooler to a Hurth 100 / ZF10

[Bill Shreeves]

Along with the installation of a new ZF 10 on my '87 Cat34, I want to add a cooler and I plan on buying the OEM 3306107001 ZF Transmission/Gear Cooler from Mr Cool.

Since I don't have one on my ZF 5 and new to this, I'm not sure how the raw water lines are run.  I'm pretty sure it's added as a loop before the heat exchanger however, I'm not sure and the last thing I want to do is restrict or reduce cooling to my engine.  Can someone help me out with a description or diagram or photo?

Also, the connections for the product shown in the picture on Mr. Cool don't appear to be very long.  Will I have a tough time getting two hose clamps on each connection on the cooler?

Thanks

[Noah]

Why the desire/need for a cooler?

[Bill Shreeves]

Noah-
I'm open to other thoughts on this but, this is the way I'm looking at it.   In addition to the new gearbox, new damper plate, shortening the shaft to accommodate the 1" longer gearbox, a new Federal Flexible Coupling and a new cutlass bearing, I mine as well finish it off with a cooler since the mfg makes one for this model.  These gearboxes hold very little ATF and the cooler it can run, the better.

[Noah]

I am not qualified to give advice on this just wanted to hear pros/cons to gain some knowledge. On the face of it, installing  a cooler appeared to be an unnecessary expense and machinery complication for our boats, but...?

[Stu Jackson]

Bill, I run an M25, a mere 2 HP less than your engine.  We ran it for 165 engine hours motoring up the coast from San Francisco to Vancouver Island over the course of six weeks (five actually moving due to bad weather before we left No. California, keeping us in port).  We ran at 2800 rpm, a tad over my normal 2650 rpm cruising rate.  The engine and transmission did just fine, some days were 13 hours, most 10, some 5.  I believe you are introducing more potential issues with a piece of unnecessary added gear, with little room and more connections.  Our boats are easily driven and sail well in light air, so motoring is "easier" on the engine, too.  You may want to reconsider your choice.  Just because they make it doesn't mean you need it.  In my 18 years of ownership, and 15 here on this forum, I do not recall anyone doing it.  I haven't done a search on it yet, though.    I now have 3244 engine hours, bought the boat back when it only had 888.

[Bill Shreeves]

Stu-
You make a very good point.  No cooler on your gearbox?  Curious, are you running a 50 or 100?  I assumed that the Catalina's with the Hurth 100 / ZF 10's had coolers installed.  No?

[lazybone]

Run your boat for an hour.  Put your hand on the gear case.  See if it hurts or buy an infrared thermo.

[Bill Shreeves]

I have an infrared thermo and will likely do that after I commission her.

BTW, any suggestions on what ATF?  I have the list of approved by ZF and thinking I'll go with "MOBIL DELVAC SYNTHETIC ATF"

[Ron Hill]

Bill : I know of no factory installed Xmission cooler on any Catalina!!

I put 5000hrs and 20 years on my M25XP engine before I changed it out because of the internal engine seals leaking.  The Hurth 50 was still going strong with NO problem.
BTW, the 35 hp M35BC engine in the C34 MKII with a ZF10 transmission does not come with a transmission cooler!!

Think you could spend these extra boat $$ on something else - My thoughts

[Bill Shreeves]

Great info guys!  Unfortunately, I have little experience yet so, I'm left with reading forums to try my best to make informed decisions.   I've read so many posts, in a variety of forums, about these Hurth / ZF gearboxes going bad early in their lifecycle, I figured I should do everything I can to protect it.

If coolers aren't typically used, as I assumed they were, and most get a good number of years out of these gearboxes, maybe I'll put the boat bucks elsewhere.

Thanks for all the info!

[Stu Jackson]

...................No cooler on your gearbox?  Curious, are you running a 50 or 100?  I assumed that the Catalina's with the Hurth 100 / ZF 10's had coolers installed.

Yeah, sometimes reading too much can give ya a headache, while at the same time we've been preaching for folks to read more! 

We have the original 50.  Don't know about the 100s because most if not all our C34s had 50s, while other Catalinas may have had 100s, but then they switched to (gasp!) Yanmars.

As another reading experience, the C36 guys have had a lot of damper plate issues, while we have been relatively free of their recurring nightmares.  Most of those were on M35 engines, IIRC.

Yes, they don't take a lot of fluid, but that's how they are designed.

ATF has to be Dexron.  Not too hard to find.  I think they're up to Dexron IV by now.  A quart goes a long way if you don't have to winterize by filling it up.

[Bill Shreeves]

ATF has to be Dexron.  Not too hard to find.  I think they're up to Dexron IV by now.  A quart goes a long way if you don't have to winterize by filling it up.

According to ZF's lubricants list for marine transmissions, it doesn't have to be Dexron although many are.

Here's the shortcut to their lubricant list     http://www.zf.com/global/media/en_zf/lubricantslists/TE-ML_04.pdf

[Indian Falls]

can't resist adding my 2 cents:
Is it possible it is supposed to warm up and run at a warmer than ambient temp so that the tolerances are where they belong?  Adding a cooler will keep it cool but is it supposed too be that cool?  Unless your clutches are slipping, gears turning in oil should not really develop any heat, especially at the turning speeds in this application. Being connected to the engine block probably inputs more heat to the gearbox than the gears ever would.  If it were me I wouldn't waste my money.

[Ron Hill]

Bill : 5000 hrs on a transmission is a lot of shifts!!! 
So as I found out the transmission outlasted the engine!!

Most transmission slippage problems are cause by not having the proper adjustment of the cable at the transmission!! 
Remember the top hole in the shifter arm on the transmission gives the best mechanical advantage, while the lower hole gives the greater throw!! 
You'd be surprised how many C34/36 owners changed to the stainless Edson shifters at the wheel and never checked to see what was happening at the transmission!!!!!!!!!!!!!!

Everything I've seen on Hurth 50, Hurth 100, ZF 5, ZF 10 transmissions have all said to use Dexron transmission fluid!!

A few thoughts.

[Bill Shreeves]

This feedback, 2 cents etc. is exactly what i hope to get in this forum!  Thank you!  I think I'll skip the cooler.  I just hope I can get thousands of hours out my new ZF10 like you guys got from your Hurth 50's.

Think there's anything to some claims that the thrust washers in the new gearboxes only have a thin plate of brass and the older ones were solid or much thicker plating giving a greater lifecycle?