HURTH ZF HBW10 Transmission Replacement on Perkins 4.108

Capt jgw · Apr 21, 2020

Check out New Age PRM transmissions. Last year I replaced my Hurth HBW5 with a PRM60D, got it from ASAP Supplies in the UK. Was only about $450 US. Near drop in replacement, the only difference is the shift lever is on the opposite side and the "drop" is 1/4" more, meaning you have to raise the whole engine 1/4". Just screw the nuts out that much on the engine mounts. The HBW10 is a little longer and heavier duty than the HBW5, but probably PRM has a replacement for that one too. (PRM90?) Betamarine uses PRM on some of their models and other users have given rave reviews. They have cone clutches rather than the disc clutches in the Hurth, more like the Kanzaki gears used on Yanmar engines. Much more robust and reliable. Rebuilding the Hurth will be more expensive and you will then have a rebuilt Hurth, which is pretty much worthless. They were junk right from the factory.

sesmith · Apr 21, 2020

Does the HBW10 cross over to one of the ZF transmissions(maybe ZF12m)? If so, you may still be able to find a new ZF replacement. There's an ebay seller that has new ZF12m transmissions for sale. IF you are looking for a rebuilder, we have a guy locally here who was factory trained and is reasonable. (Chris Jones Marine, Summerville, SC). He just rebuilt my ZF15m for me. He might also be a good contact to find a new or used one. I almost went the new Twin Disc Technodrive replacement route, but decided to rebuild instead, for better or worse (haven't put the tranny back in the boat yet this spring). My main reason for rebuild was that the gear ratio of the Twin Disc unit was just enough different that I was afraid I would be opening up a can of worms with having to change prop.

justsomeguy · Apr 21, 2020

Got a service manual?
Tear your existing tranny apart and see if you can't repair it first. You'll never know unless you make the attempt.
I've learned quite a bit about my engine and my tools (or lack thereof) via this method.

sesmith · Apr 21, 2020

Respectfully disagree with the above

. I was a factory trained Mercedes Benz tech in a previous life, so I should have bonded with the whole ZF German thing of doing my own tranny rebuild. Truth is, these little transmissions are pretty complex and tolerances are tight. Rebuild parts would have set me back around $1k, so if I screwed it up, it would have been a pretty expensive lesson. So I paid a guy who knew them inside and out to do it (right, hopefully) for not a heck of a lot more.

justsomeguy · Apr 21, 2020

sesmith said:
Respectfully disagree with the above

I appreciate your respect, but if a replacement is inevitable, how much might the OP be out if he simply makes the effort?
Besides, it's what men do.

sesmith · Apr 21, 2020

justsomeguy said:
Besides, it's what men do.

TomY · Apr 22, 2020

LaLuna618 said:
It turns out I was mistaken, the existing transmission is an HBW 100 2-R at a 1.79 ratio. From everyone I've talked to the exact replacement is a ZF10M, but not a new one since those are at a 2:1 ratio and I want 1.79.

I think I will try to replace the transmission myself if I can find an exact fit replacement. Question for all you is, will I need to move the engine at all to do the swap or will the transmission just slide right out after I've unbolted it?

It will need to slide aft far enough for the shaft to clear the engine. That's about 2" or less on my transmission, which I removed a few times for various reasons.

It might take a little prying to get it moving. A stiff scraper tapped on the seam between the bell housing on the engine and gear case works for me.

Once the splined transmission shaft end comes out of the engine disk, you hopefully will be able to back the transmission out. Do you have space to pull it out of the engine compartment without moving the engine?

FastOlson · Apr 22, 2020

IF.... you are removing the trans and either rebuilding or replacing it, be *sure* that you replace the torque plate while you have access to this.
Plan B -- you might have to lift and move the engine into the main cabin. I did that, albeit as part of preparing to lift it out and replace the drive drain with a new Beta. We used the main halyard to lift about 270# of obdurate Universal 3 cylinder diesel, after I removed the alternator. It proved to be an awesome opportunity to clean up the whole engine bay and replace the old sound-deadening mylar/foam.
There are some pix and notes about this on my blog; pm me for a link.

sesmith · Apr 22, 2020

On ours, I had to jack the back of the engine up enough so the back of the transmission would clear the coupling. Then I could slide the transmission back far enough to get the splined input shaft clear of the damper plate on the engine. Only needed to go back a couple of Inches, as Tom mentioned. I did use the opportunity to replace the cutless bearing, PSS seal, and damper plate while I was at it. Had to cut the shaft for that work, so it's also getting a new shaft and coupling this spring when I finally get back up north to finish the job.

justsomeguy · Apr 22, 2020

sesmith said:
On ours, I had to jack the back of the engine up enough so the back of the transmission would clear the coupling. Then I could slide the transmission back far enough to get the splined input shaft clear of the damper plate on the engine. Only needed to go back a couple of Inches, as Tom mentioned. I did use the opportunity to replace the cutless bearing, PSS seal, and damper plate while I was at it. Had to cut the shaft for that work, so it's also getting a new shaft and coupling this spring when I finally get back up north to finish the job.

Out of the water, I'm surmising.

Mine was hoisted via a cockpit winch with a baseball bat easing the rope's turn over the companionway threshold. Threshold, right?

Separate the shaft from the output flange and drive it aft, giving me the needed inches to pull the tranny.

sesmith · Apr 23, 2020

On mine (Catalina 350) all I had to do is take the nuts off the rear motor mounts, and use long bolts through extra holes that are in the motor mount brackets on the engine. Add a nut and washer under the mount bracket, and push against a piece of wood placed on the beam (blanking out on the proper word tight now) that supports the motor mounts. Screw the nut up on each side (which was a painfully slow process in cramped quarters) and the back of the engine is raised up. I've also heard of people putting a deflated soccer ball under the engine and inflating it for a jack. That would have been plan B. Lifting it from above plan C.

FastOlson · May 14, 2020

LaLuna618 said:
Thanks for all the helpful feedback! Turns out there was water intrusion damage to the engine itself. Mechanic recommendation is full repower, but man would I like to avoid that.

Any thoughts on how to repair engine vs full repower?

Thanks!

FWIW, s Shannon is a 'high end' boat, and a repower would maintain or even increase its value. Of course it's easy for me to advocate your $ expenditure!

Our calculation on replacement was that totally going thru our old and still running Universal was going to cost well over half what a new Betamarine would cost, so we went with the Betamarine. Engine, trans, control panel, and long warranty.
Our goal is to keep using the boat long enough to amortize it out -- in satisfaction if not in $$. Admittedly, this "calculating" is different for every boat owner...