Steps for Replacing my HBW50 transmission with ZF 12M

[LouBegue]

I just purchased a 2016 Catalina 310. One week after purchase, the transmission went bad. I had a feeling something was wrong with it. I purchased a new ZF 12M transmission and damper plate. I am debating whether to attempt the replacement myself or have the marina mechanic do it. Can someone give me some info on what this job would entail? What can I expect? What are the steps for removing the old transmission? What needs to be removed? Do I need to remove the bell housing? Do I need to lift the engine? I really appreciate any info.

 

[u0958901]

Damper Replacement - Catalina 350 International Association

 

[LouBegue]

Damper Replacement - Catalina 350 International Association

This is awesome info.

 

[u0958901]

Different boat model and engine but the process is the same.

 

[dlochner]

Replacing a transmission is essentially a nut and bolt operation. Unbolt a bunch of stuff and bolt the new stuff in.

The most challenging parts are separating the flange from the shaft and realigning the engine if it needs it.

When we replaced the transmission on our Yanmar it was necessary to replace the bell housing with a couple of adapter plates as the bolt pattern on the ZF 12M was different from the original. It was also necessary to change the flange because the dimensions were subtly different.

While you have every thing apart consider replacing the flange anyway with a split flange. It is easier to install and remove. Spray the new flange with a anticorrosion spray, like CRC Anticorrosion, after it is installed.

 

[Ward H]

Are you aware of the size differences between the HBW50 and ZF 12M?
Catalina Direct shows this:
"Important differences when compared to HBW 50 transmission
• Front to back (L + L3) : +37mm (+1.46")
• Output shaft drop from crank: +10mm (.39") Will require raising the engine 10mm
• Reduction ratio 12M vs HBW 50: 2.14:1 vs. 2.05:1"

Those differences don't sound like much but length alone could be a problem, especially if you have to move the engine forward as then you would need to raise it higher than the .39" listed.
That or you would need to take out the 1.46" of shaft somewhere. If it can't be taken off the flange, then where?

@dlochner On my C30 the 12M would require major work. Was it easier on your Sabre?

 

[Hollyberry]

Also....if you're doing it afloat and if you have a dripless shaft seal (PYI or similar) you need to secure it before you lose the force on the bellows when removing the tranny .

 

[dlochner]

@dlochner On my C30 the 12M would require major work. Was it easier on your Sabre?

This was a job I hired out (which was screwed up by the yard big time) so I didn't follow the progress that closely. There was a mating issue the engine, which was solved by 2 adaptor plates. The overall size was and location of the shaft output was not a big issue. I think it pushed the prop shaft out about ¼" which is not an issue. Extending the shaft out 1.46 inches would be an issue. The size might have been compensated by the difference in the connection to the engine.

The other issue to be concerned with is the forward gear ratio. If the ratio is different it may require a new prop or re-pitching the existing prop. We have a Max Prop, so it was easy to change the pitch. If you have fixed blade prop, it will mean a trip to the prop shop and possibly a new prop.

The original transmission had a more traditional bell housing that was deeper than the replacement.

Here's the original post mortem.



And here is the new one. One advantage to the new installation is the ease with which the transmission can be removed, all of the mounting bolts are easily accessible. On the original the two lower bolts could not be removed without raising the engine a couple of inches. The new transmission bolts to the smaller plate which in turns bolts to the larger plate which bolts to the engine.



To answer the original question, this is mostly a remove and replace operation. If you can swing a wrench and a ratchet you can do it. The tricky part is getting the right parts and making sure they all fit correctly. There is probably a good marine transmission shop near you that can help get the right parts.

While I hired a yard to do the replacement, it was only because we were traveling and several weeks from home. It would have meant working in an unfamiliar yard, in an unfamiliar town, without access to my tools and rudimentary shop at home. I did pull the transmission one year to have it rebuilt and would not hesitate to do it again nearer my home.

 

[dlochner]

Also....if you're doing it afloat and if you have a dripless shaft seal (PYI or similar) you need to secure it before you lose the force on the bellows when removing the tranny .

I did remove my transmission while floating and do have a PSS shaft seal. The weight of the prop and shaft was enough to keep the seal closed. It did leak some if the shaft was out of position, but it wasn't a problem in the long run. Just for a few flooding minutes until it sealed.

 

[Calif. Ted]

A friend just had to do this with his mkii C30, he'd had original trans rebuilt about 12 years ago and it failed last winter. He had someone do the replacement while it was in the water, fit was a problem and after consultation with the factory there was a grinder used to make it fit. Took a long time to get it accomplished.

 

[Hollyberry]

I did remove my transmission while floating and do have a PSS shaft seal. The weight of the prop and shaft was enough to keep the seal closed. It did leak some if the shaft was out of position, but it wasn't a problem in the long run. Just for a few flooding minutes until it sealed.

Still a potential for a fair amount of leakage if somehow things get misaligned - esp if nobody aboard. We got away with the the first night but I had a bit of an 'oh shit' moment when I accidentally nudged the shaft the next morning. A bit of tape is a simple prevention.

 

[Ward H]

I agree that removing the transmission for rebuild and reinstalling is just wrenching.
Replacing with a different transmission with different offset and length may be more than just wrenching. If I had gone with the 12M I would have had to do a lot of cutting, fiberglassing and finishing.

I found the Twin Disc TMCC40 which had minimal offset and even less length to adapt to. It was just wrenching because it was sized so close to the original.

 

[SimiSAilor]

Hi Lou,

I made the swap a few years ago. It was a lot of work, but doable. It is a good time to replace the damper and engine mounts.
First remove the fire wall bulkhead, watch out for hidden screws. Separate the prop shaft from the trans at the coupler and move the shaft aft as far as possible, unbolt the engine mounts from the hull and slide the engine forward a few inches. Don't disconnect anything on the engine. Now you should have enough room to unbolt and slide the transmission aft far enough to clear the input shaft on the engine side. This also provides access to the damper plate bolts. Please reference the owners manual for the specs on engine alignment and dimensions for setting the engine height in the engine mounts. I needed to shim the mounts up to get within specs. Getting the prop shaft coupler aligned was a major task, took me a long time.
With the new damper and mounts and correct idle speed there is no vibration.

Now for the issues I found. My prop shaft zinc was installed forward of the cutlass bearing strut and had to be removed to enable the shaft to slide aft. I also had to fabricate a new bracket to hold the shift control cable. Another issue to watch for is the shaft log hose that holds the gland nut. I replaced this hose and the four clamps, obviously at the first haul out, with as short a hose as possible. Now repacking the gland nut is doable, still not easy. Yes, the prop now sits a little farther aft, it works just fine.

The short answer is no you don't need to remove the bell housing and no you don't lift the engine much. I rigged a 4x4 over the hatch with a come along to help "reposition " the engine and swap the engine mounts.


.

 

[LouBegue]

Hi Lou,

I made the swap a few years ago. It was a lot of work, but doable. It is a good time to replace the damper and engine mounts.
First remove the fire wall bulkhead, watch out for hidden screws. Separate the prop shaft from the trans at the coupler and move the shaft aft as far as possible, unbolt the engine mounts from the hull and slide the engine forward a few inches. Don't disconnect anything on the engine. Now you should have enough room to unbolt and slide the transmission aft far enough to clear the input shaft on the engine side. This also provides access to the damper plate bolts. Please reference the owners manual for the specs on engine alignment and dimensions for setting the engine height in the engine mounts. I needed to shim the mounts up to get within specs. Getting the prop shaft coupler aligned was a major task, took me a long time.
With the new damper and mounts and correct idle speed there is no vibration.

Now for the issues I found. My prop shaft zinc was installed forward of the cutlass bearing strut and had to be removed to enable the shaft to slide aft. I also had to fabricate a new bracket to hold the shift control cable. Another issue to watch for is the shaft log hose that holds the gland nut. I replaced this hose and the four clamps, obviously at the first haul out, with as short a hose as possible. Now repacking the gland nut is doable, still not easy. Yes, the prop now sits a little farther aft, it works just fine.

The short answer is no you don't need to remove the bell housing and no you don't lift the engine much. I rigged a 4x4 over the hatch with a come along to help "reposition " the engine and swap the engine mounts.


.View attachment 216754View attachment 216756

Hi Lou,

I made the swap a few years ago. It was a lot of work, but doable. It is a good time to replace the damper and engine mounts.
First remove the fire wall bulkhead, watch out for hidden screws. Separate the prop shaft from the trans at the coupler and move the shaft aft as far as possible, unbolt the engine mounts from the hull and slide the engine forward a few inches. Don't disconnect anything on the engine. Now you should have enough room to unbolt and slide the transmission aft far enough to clear the input shaft on the engine side. This also provides access to the damper plate bolts. Please reference the owners manual for the specs on engine alignment and dimensions for setting the engine height in the engine mounts. I needed to shim the mounts up to get within specs. Getting the prop shaft coupler aligned was a major task, took me a long time.
With the new damper and mounts and correct idle speed there is no vibration.

Now for the issues I found. My prop shaft zinc was installed forward of the cutlass bearing strut and had to be removed to enable the shaft to slide aft. I also had to fabricate a new bracket to hold the shift control cable. Another issue to watch for is the shaft log hose that holds the gland nut. I replaced this hose and the four clamps, obviously at the first haul out, with as short a hose as possible. Now repacking the gland nut is doable, still not easy. Yes, the prop now sits a little farther aft, it works just fine.

The short answer is no you don't need to remove the bell housing and no you don't lift the engine much. I rigged a 4x4 over the hatch with a come along to help "reposition " the engine and swap the engine mounts.


.View attachment 216754View attachment 216756

Thanks so much for this info. Did you need a new adaptor housing or did the original one fit?

 

[SimiSAilor]

The 12M bolts directly to your existing bell housing. No adapter or modification necessary.
Jeff

 

[jviss]

If it's just a bolt on, you are lucky! If I have to replace mine it's a new bell housing for around $1,0000, and lots of fiddling.

 

[RitSim]

I changed my ZF trans on my C30 a few years ago. Replaced it with a Twindisc and was very happy. I raised the engine with a deflated soccer ball and then blocked the engine. I bought a damper plate on-line by matching pictures and dimensions - worked great. Replaced a lot of rusted metric bolts (Bolt Warehouse I think). On my boat, I had to remove the bell housing because the transmission was bolted to the Bell housing from inside. I created one issue by overthinking- I added lock washers to those bolts and there wasn't sufficient room between the bolt heads and the rotating parts. Had to take it all apart again.
The only other issue was that the Twindisc shift lever (don't remember here) was either opposite side or opposite function causing a minor change in the cable support.

 

[LouBegue]

The 12M bolts directly to your existing bell housing. No adapter or modification necessary.
Jeff

So good to here!

 

[LouBegue]

I was so impressed with all the responses to this post. Thanks everyone for your input. I finally got around to doing the transmission install and everything in this thread was spot on. The ZF12 transmission was an exact bolt on to me Universal M25XPB. The original adapter plate fit perfectly. The fiberglass tab underneath the transmission needed to be trimmed to give the larger ZF12 transmission room seat. This was an easy adjustment. The shaft needed to be moved aft about 1.5 inches to allow for the 37mm longer transmission. The engine needed to be lifted up a about 5 inches so that the new transmission could be attached to the engine which was also a very easy procedure. I would say the most difficult thing was wrenching the bolts on the transmission because of the tight space to work with. It was recommended by everyone that if you do this job, replace the damper plate... Very good advise. The splines on the old adapter plate were severely damaged.

Is anyone interested is purchasing a used HBW50 that needs a rebuild? Make me an offer. ¯\_(ツ)_/¯