Hurth Transmission engagement issue

Capt.Will

Active Member
Aug 15, 2016
148
Lake St. Clair
Boat Info
1997 Sea Ray 330 Sundancer
Engines
7.4 MPI Mercruiser Inboards
Vessel: 1997 Sea Ray Sundancer 330

Engine: 1997 7.4L Mercury Bluewater MPI

Transmissions: Hurth V Drives

Incident One: September 15 2021, From a cold engine start leaving my dock the STD transmission would not engage. After shifting in and out of forward and reverse several times it eventually engaged. After reaching my destination I checked the fluid in that transmission and discovered it was quite low. I topped it off and it worked fine from there on.

Incident Two: October 27 2021, same thing as before. STD transmission would not engage until shifting several times. I checked the fluid and it seemed to be at an acceptable level. I had about a ten mile voyage to make and at about 8 miles into it I suddenly started to lose power from the STD side. The boat started to list rapidly but my engine RPM didn't seem to change. I almost immediately brought down to idle speed and shut engines down the check fluid level. Seemed fine. I started back up after about 5 minutes and it planed fine and I made it to my destination.

*The time between the two incidents, I used the boat every weekend with no issues.

Could this be a sign of a failing transmission? Bad fluid? (I changed fluid last season). Clogged transmission filter?

Any ideas, comments or similar situations shared would be very helpful.
 
Clutch plate slipping due to low ATF pressure? Might flush the fluid and filter and replace with clean new ATF.
But first....
Check that the shifter cable is moving the lever fully forward or back. Might need adjustment. Unhook the cable and see if the lever can move further forward or back.
 
Clutch plate slipping due to low ATF pressure? Might flush the fluid and filter and replace with clean new ATF.
But first....
Check that the shifter cable is moving the lever fully forward or back. Might need adjustment. Unhook the cable and see if the lever can move further forward or back.

Excellent advice. Thanks so much for that. I will do all of those procedures.
If there is any other words of wisdom out there please let me know. Thanks again.
 
Does anyone know where I can find a digital copy of the manual for these transmissions? I’ve done some searching and have come up short.
 
Does anyone know where I can find a digital copy of the manual for these transmissions? I’ve done some searching and have come up short.

Double check your model number to see if this is the correct manual...
If it's correct, I can email you the PDF. CSR won't let me upload it because it's too large.

Or, go here...
https://www.manualslib.com/manual/1301631/Zf-63-A.html

Chapter 9 - Troubleshooting
 

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Double check your model number to see if this is the correct manual...
If it's correct, I can email you the PDF. CSR won't let me upload it because it's too large.

Or, go here...
https://www.manualslib.com/manual/1301631/Zf-63-A.html

Chapter 9 - Troubleshooting

I confirmed my transmission as model: HSW 630 V1-1.55
Let me know if you would be able to send over that manual. Thanks so much.
 
Clutch plate slipping due to low ATF pressure? Might flush the fluid and filter and replace with clean new ATF.
But first....
Check that the shifter cable is moving the lever fully forward or back. Might need adjustment. Unhook the cable and see if the lever can move further forward or back.

Visited the boat this past weekend and confirmed the shifter cable is correctly moving the shifter completely forward and reverse.

I also removed the filter and all of the fluid from the transmission. It all seems to appear normal and clean.

Awaiting the manual from R-and-R hoping to find any other possible service points while still in the boat. I just don't hear about these transmissions failing too often around this area.

I really hope there is a procedure to find out if this issue is fatal or not. The boat is currently in heated indoor storage for the winter. My fear is if this is failing and needs to be pulled it would be extremely cheaper to have it pulled in the yard before spring launch verses launching the boat and realizing it is failing to then have to pay to pull the boat again and find another yard to pull the engine/transmission.

Any other recommendations would be greatly appreciated. William
 
Visited the boat this past weekend and confirmed the shifter cable is correctly moving the shifter completely forward and reverse.

I also removed the filter and all of the fluid from the transmission. It all seems to appear normal and clean.

This manual is the correct one for your transmission. I can't send through this website because the file is too large, but you can click on this link and it will take you to a website that has it. "Troubleshooting" is Chapter 9.

https://www.manualslib.com/manual/1301631/Zf-63-A.html
 
630’s are binary mechanisms……they either work or need to be replaced. Sometimes you can save one if you catch a problem early.

In your case the tell is low fluid causing it to slip. Where did the fluid go? If it is in the bilge, then you have a case or seal leak. If it isn’t in the bilge….then you may have a oil cooler leak where the transmission fluid is leaking into the raw water channel in the oil cooler.

If you have the original oil coolers and you do not have transmission fluid in the bilge…..that is what I would look at. Oil cooler leaks are common problems and probably have destroyed more transmissions than anything else. The problem goes from losing fluid to having water flow into the transmission lines pretty quickly.
 
These transmissions are pretty robust. I had a similar issue and it turned out to be a failing pump ( or something on the insides of that mechanism) that creates/regulates the pressure. There is no way to test/diagnose this best of my knowledge. Here is the Troubleshooting guide section that almost all symptoms point back to.

upload_2021-11-11_22-2-57.png


If you follow this in order, Replace the filter (and make sure its not sucking air), and insure correct level of fluid (not to low, and not too high...both can be bad).

After that, you get into the control block and the piston rings. Sounds bad, but for a HSW800IV the control block, a gasket and a couple of new piston rings, it was about $800. Its about a 1 hour job to swap it out.

Transmission Marine in Ft Lauderdale is a great source for parts.
 
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Many of us had the HSW 800IV and had to deal with issues with them and even replaced them with the newer ZF units, rebuilt them or as Dave @dtfeld says replaced major components. The 630 is almost identical as the 800 but a bit smaller. Regardless do not operate the boat if the clutches are slipping it will destroy the gear and you will be dealing with a very expensive issue rather than a potential simple fix. Clutches that are slipping get hot and will warp permanently which in extreme cases completely lock up the gear.
Some things in order for you to look at -
  • When you changed the fluid did you pull the bottom plug and look at the magnet? There will be small filings but should not be many and no "chunks" of iron.
  • The filter cap is a very poor design and must be sealed. That cap is under negative pressure when the gear is running. If it is leaking air the hydraulic pump will be sucking in air and not develop the correct pressure to operate the clutch packs and consequently the packs will not fully close and will slip. One indicator which reveals that cap is sealing is the gear case should be under a bit of a negative pressure after cooling down from a day on the water. You can tell by pulling the dip stick and hearing a bit of air sucking in.
  • There is a port on the control block where the pump pressure can be measured. you should have pressures above 290 psig (the Hurth gears operated at a bit of a lower pressure than the ZF shown in the graph below). The port is the plug indicated as number 12 in the below schematic. I installed a pressure and temperature transducers in mine so I could monitor those all important hydraulic fluid temperatures and pressures (see the picture).
upload_2021-11-12_7-39-16.png

upload_2021-11-12_7-46-54.png

Gear instrument cropped.JPG
 
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Did you guys miss the point that his fluid was really low? If it isn’t in the bilge it went somewhere else and the pump and clutches have nothing to do with it.
 
Did you guys miss the point that his fluid was really low? If it isn’t in the bilge it went somewhere else and the pump and clutches have nothing to do with it.
Good point! If not in the bilge then the cooler has failed. But he changed the fluid and seems it still doesn't work.
 
It has been my experience that we find ourselves responding to the middle of the story rather than the beginning. I like the 630 and it’s simplicity. That said the two sure things that will kill it are: no fluid and water intrusion.

Will’s 630s are 24 years old and we don’t know the prior history on them.

In their final stages on failing they will work sometimes and then they stop altogether because internal components have completely failed.

You can still get them for less than $3,500 which is why it is easier to replace them. ZF won’t warranty a new one unless you replace the cooler.
 
Did you guys miss the point that his fluid was really low? If it isn’t in the bilge it went somewhere else and the pump and clutches have nothing to do with it.

I did, however, seems to still be an issue. Troubleshooting guide still applies. I'm not convinced that any fluid is missing just yet, would need more info and thats because it tough to measure the fluid level in these crazy things.

So first things first. Check the correct fluid level Here is how to do it.

upload_2021-11-12_9-27-6.png
 
It has been my experience that we find ourselves responding to the middle of the story rather than the beginning. I like the 630 and it’s simplicity. That said the two sure things that will kill it are: no fluid and water intrusion.

Will’s 630s are 24 years old and we don’t know the prior history on them.

In their final stages on failing they will work sometimes and then they stop altogether because internal components have completely failed.

You can still get them for less than $3,500 which is why it is easier to replace them. ZF won’t warranty a new one unless you replace the cooler.

These transmissions are pretty tough and unless there were other symptoms, I wouldn't assume they are dying. Burnt fluid, or a prop that turns in neutral would indicate bad things, but not mentioned in this. Usually its something pretty simple and inexpensive. Hopefully this is the case. Maybe not.

Believe me, I spent a good long time trying to track down why a transmission that wouldn't stay in gear. Rebuilt the entire system from the shift levers on back on mine.

If its not the shift cable, fluid level, filter or the filter seal, then it is likely the piston rings or the control block. There is no troubleshooting guide or testing for the control block. Evidently they do go bad, but even after disassembling one, I cant figure out what would make one fail.
 
These transmissions are pretty tough and unless there were other symptoms, I wouldn't assume they are dying. Burnt fluid, or a prop that turns in neutral would indicate bad things, but not mentioned in this. Usually its something pretty simple and inexpensive. Hopefully this is the case. Maybe not.

Believe me, I spent a good long time trying to track down why a transmission that wouldn't stay in gear. Rebuilt the entire system from the shift levers on back on mine.

If its not the shift cable, fluid level, filter or the filter seal, then it is likely the piston rings or the control block. There is no troubleshooting guide or testing for the control block. Evidently they do go bad, but even after disassembling one, I cant figure out what would make one fail.
Include in that list unexplainably low fluid level and/or milky fluid.
 
This past weekend I visited the boat and removed the Control block. I have attached some photos. Problem is, I really don't know these units and do not know what is worn or not. Can someone fill me in on what these parts are? The manual really does not explain the Control Block in detail.

Pretty obvious I will be replacing all known seals, gaskets and possibly the fine filter and the cap for that.

After reading all your comments and input on this issue I am really hoping this is simply a vacuum leak from one of these components and resealing it will hopefully solve this. Any other thoughts are greatly appreciated.

Also, does anyone have a great resource for purchasing these parts?
 

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Well, I found Marine Parts Source online that I made the purchase of O-Rings and gaskets. I also ordered the filter cap assembly because mine is rusty and may be a problem. $177 FREAKING bucks for it. Outrageous. Even EBAY was pricing it for that amount. I sure hope this solves the problem.
 

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