Drive shaft,Transmission noise when cold.

[never monday]

38ft and 20k # is outside the range I would use an M3-20B.

It can take time (running hours) for a problem to develop. The ZF5 is out of production now.
What RPM and speed can you achieve? what are the prop specs?

[AnchorageGuy]

Our former sailboat had a Hurth transmission and it always sounded like it had rocks in it when we first started it up and put it in gear. After 17 years of no problem we just ignored it. Not saying you should, just offering our experience. You have yet to say if you have checked the prop to see if it is fouled.

[highseas]

I dont follow,an M3-20B is engine.Top rpms are about 2600 or so,I never run over 2100 at cruising speed.Ran a little higher a few weeks ago trying to catch tide through Dodd narrows,once noise did its initial rattle routine. it ran fine at upper end.its a Campbell 3 blade prop, not sure of specs at this time,apparently all was matched for this setup.When I look at Hughes Yachts diagram of hull profile,it definitely shows more than 2in.of shaft exposed,looks like the 3to 4 in. i remember seeing when boat was out of water.Water is a bit cold and gross here so no I havnt looked at prop lately,noise would be constant,no?Probably need ZF6 M or ZF10 M.Will probably reinstall and get boat back to guys who did install to figure it out.

[highseas]

Chuck,how long did your rock crushing Hurth make noise when you put in gear,did it just stop after a bit.?Have read many reports of premature failure and noisy velvet drive models.Ok I get it,boat is underpowered,this was a concern of mine before purchasing.Actual weight is about 18000lbs.,before stores etc.Former owner wanted to use 30 hp,but wouldnt fit into space under floor.Boat does slip through water easily at 6kn. , 2100rpm.Like I say though,hours of motoring without even a sign of trouble.

[never monday]

Originally Posted by highseas

I dont follow,an M3-20B is engine.Top rpms are about 2600 or so,I never run over 2100 at cruising speed.Ran a little higher a few weeks ago trying to catch tide through Dodd narrows,once noise did its initial rattle routine. it ran fine at upper end.its a Campbell 3 blade prop, not sure of specs at this time,apparently all was matched for this setup.When I look at Hughes Yachts diagram of hull profile,it definitely shows more than 2in.of shaft exposed,looks like the 3to 4 in. i remember seeing when boat was out of water.Water is a bit cold and gross here so no I havnt looked at prop lately,noise would be constant,no?Probably need ZF6 M or ZF10 M.Will probably reinstall and get boat back to guys who did install to figure it out.

if the engine were not physically connected to the trans and providing the power to drive it. You would have a valid point.

The M3-20B has a continuous rating of 3600RPM and should be propped to achieve this. The cruise RPM will be around 2800-3200 RPM.
For now you are overloading the and lugging the power unit. Please reprop to achieve the rated RPM then report back about your gear box noise.

[highseas]

Still doesnt explain why noise dissapears after a short time.Will find out about prop on tuesday from marine mechanic who did install.Not sure I follow,what is noise source then, engine or prop?

[never monday]

Let me see if I can explain this better. if it comes off condescending it isn't.

First, the power unit (eng & trans) is being run out of spec. This in it's self can be the root cause of problems.
Next. A Universal (Kubota) has some roughness to the idle until it is warmed up. This is normal.
Now, with running it out of spec (low) your lugging the engine. To associate the problem. Go drive a car up hill in top gear at 1500rpm. The whole car will shake and complain. It's hard to determine what exactly the problem is.

Put the power unit in spec then we can discuss what's wrong. For now it's operator/installer error.

You never said what speed you can get at 2600 RPM

[highseas]

I believe at full throttle around 26 or 2700rpm,she goes about 7kn.This I think is about hull speed.Going to drain trans. and check for bits,as now it is out I can access lower drain plug,then will reinstall for more evaluation.Have totally babied my shifting since I took possession of vessel,not operator error thats for sure.Still does not explain noise not being constant.Have read many reports of noisy Hurth gears,whats up with this?Does not feel like engine is lugging.When you say roughness is normal,why?At idle mine is fine,its upon acceleration above 1500 in gear it gets chattery,rattly,ringy sounding.It seems like after a bit if I overrev above 2100(cruising speed) briefly a couple of times,noise suddenly vanishes.Will do more seatrials next week to try and get better idea what is actually going on.Just dont want to have to call tow boat.Thanks for your input ,any ideas,advice are getting me more informed.Not sure why it is set up way it is.

[never monday]

why are you not listening to what I'm saying? I do this for a living! 6 days a week.

I'm going to put it in simple terms because your not catching what I'm spelling.

you are over pitched stop chasing a white elephant and get the boat right first!

set the drive line so power unit operates in the correct range then it can be evaluated if there is a problem.

also "babying" your shifts is not the way to shift. Read the study hall at the top on transmissions.
All Kubota based engines have a more coarse vibration at cold idle than at hot idle.

I'm done with the free advice, your not listening anyway.

[highseas]

Thanks ,and yes I am listening to you,and the noise.As I said I will talk to installer asap as to why it is propped this way.Right now Im trying to cover all my bases,before shelling out cash.I understand about pitch and soforth.When I say babying shifts I mean I always make sure engine is idled down first.Im a sailor not an engine mechanic!

[highseas]

Turns out Hurth transmission is toast after only 260 hrs,and no warranty.Even though ATF was regularly changed,metal filings destroyed all surfaces,(either bearing or clutches bits).Prop is also too big,as "never monday" suggested,not sure why previous owner did this.Either wasnt fully engaging into gear ,or alignment issues are apparent reason for failure,which I find hard to believe.I think more likely cause is oversize prop.Probably have to upgrade to ZF6M,as 5 no longer made.Prop size will likely be reduced to around 13x6 3 blade.According to Hurth,only in emergency should you shift gears with rpms up,although its not recomended.The suggested upgrade motor for this boat is only 3hp. more than what I have,many sailboats have smaller engines and do just fine.

[never monday]

I have an HBW50 parts trans. Shipping would be tough

[Chief Engineer]

Not to be crass, but I think I might be looking for another "installer"

[highseas]

As it turns out ,it was owner (former)installed.All seemed normal first 3 months.Install looks professional,had vessel survey ,but not on engine/driveline.Barely broken in and already broken.Not sure what the ZF6M runs at$wise,gotta make sure ratios match up.

[never monday]

I wouldn't worry about matching your current ratios. They obviously didn't work the first time. Get with a good well respected prop shop. Have them run the hull /weight / prop profile and get the best gear/prop combination.