Oday 34 transmission removal

Davidasailor26 · Nov 17, 2015

Did you sail with the engine in forward at any point? If so you may have worn the clutch causing the slippage. If not, it may have worn itself over time. In either case you could try something Hurth recommended to us years ago to roughen up the plates:

Remove all the existing fluid and replace with diesel. Run the engine for about an hour, occasionally shifting between gears. The remove all of the diesel and replace with regular fluid. We've had success doing this under similar symptoms to yours. Good luck.

jibes138 · Nov 17, 2015

Scott, Try posting this in the Engines and Propulsion forum, there are a lot of mechanics hanging around there that can help. I don't have much to offer in this case other than it sounds like a rebuild. The cost of new might be a high percent of the cost of a whole repower. You might want to start searching for any used trannies from a derelict.

Panta Rei · Nov 20, 2015

Removing a transmission is not all that hard providing you can get at it. I removed mine while laying on top of the engine. Lots of old boat cushions. Swapping out the transmission should take no more than the better part of the day. Of course try the diesel trick first. This is a great site for all sorts of help. Foley's prices are higher than others but the website is very helpful.
http://www.foleyengines.com/resources/tech-tips/hurth-gears-care-and-maintenance
I purchased a new transmission since it was in the middle of the season and I had trips planned. Rebuilding is likely a better way to go $$ wise. Remember to carefully inspect the dampener plate. Most say it should be replaced while you have the transmission off. I replaced mine since it had a broken spring and was making that pinging noise at idle.
Please post results of the diesel trick. You might want to ask the Foley people about it and see what they say. My guess is that they don't recommend anything that does not require your credit card.

colinhulse · Nov 22, 2015

I rebuilt mine. There are metric single ball bearings that I sourced from England. I found the spring clips in Fla and the bearings from a local supplier. The clutch plates were very pricey. There are two thrust bearings that are steel with a thin layer of bronze. I had a machine shop make them out of Aamco 17 bronze. you also need a set of shims to set the proper end play. I would guess that end play is huge in your unit. It is not that hard to rebuild but requires careful planning. I did mine over the winter.

Panta Rei · Nov 23, 2015

http://boatinfo.no/lib/gear/manuals/hurth-5-10-20.html#/50

This will give you an idea as to what it takes to service your unit.You might want to try a local small engine or Turf equipment repair shop.

Panta Rei · Nov 23, 2015

SailingCal21 said:
Yeah, I'm pretty good with engines, not so much with transmissions, too many moving parts. When I R&R the transmission I'll go with a new ZF 12M. I did find a site with R&R information of a Hurth HBW 10 with the ZF 12M, however the vessel is a Corbin 39: http://www.zentozero.com/2013/06/replacing-hurth-gearbox-with-zf-12m.html Looks like the fit is the same which is one of my concerns.

I read the corbin 39 blog. It's dead on including the frustration of placing the bell housing and transmission back onto the engine. The splines must align to slide the assembly into place. Mine finally did just as I was running out of strength to lift the thing one more time.

jibes138 · Nov 23, 2015

Scott, I was looking at my tranny yesterday thinking about your problem. What a PITA to try to get it out. I have a good friend that is a chiropractor, my guess is you're going to need one by the time you get done with this project. If you take out the batteries and heat exchanger can you squeeze in there all crunched over to get it out? Might be easier to pull the engine out and then put it back in.

Panta Rei · Nov 24, 2015

jibes138 said:
Scott, I was looking at my tranny yesterday thinking about your problem. What a PITA to try to get it out. I have a good friend that is a chiropractor, my guess is you're going to need one by the time you get done with this project. If you take out the batteries and heat exchanger can you squeeze in there all crunched over to get it out? Might be easier to pull the engine out and then put it back in.

This is getting interesting. I searched the internet for a picture of the 34 engine compartment. It sure is tight.
Here's a heads up that might be helpful.
Once you disconnect the shaft which you said you have been able able to get at to loosen the bolts, you are then left with just 5 accessible bolts holding the bell housing on. I think your issue will then be getting the bell housing and transmission assembly out of the engine compartment. You may have to remove the transmission from the bell housing while the assembly is trapped in the engine compartment. If this is the case, removing the engine might be worth considering.