Universal M-30 Clanging Noise

[Quadrille in JB]

My universal M 30 makes a clanging noise after I shift from reverse to forward when backing out of my slip. The RPM is low but when I increase the RPM it ceases after about 15 seconds and the engine runs smoothly.
I have just changed the torque plate, added a Federal Transmission vibration shaft damper, and changed the Cutless bearing. The shaft coupler to transmission alignment is good and there is no vibration in the shaft. The problem was present before I made these changes and it’s still there.
This just happens when backing out of the slip and immediately after shifting to forward.
The frequency of the clanging sounds about right for the shaft rpm.
Has anyone experienced this?
Does anyone have any good ideas on how to correct it?
Thanks for your responses in advance...

[a64pilot]

What kind of prop?

[boden36]

Is the prop nut tight?

[Quadrille in JB]

It’s a 2 blade 16x12 and the nut is tight. This pic was taken yesterday morning before splashing.
Thanks

[Tetepare]

Sounds like you are pretty savvy but I’ll ask anyway did you check the motor mount nuts?

[Boatyarddog]

Originally Posted by Quadrille in JB

It’s a 2 blade 16x12 and the nut is tight. This pic was taken yesterday morning before splashing.
Thanks

Question, did you paint over your shaft zinc?
Its not gonna work well like that.
Check to see if the shaft is clanging against the packing gland.
SV Cloud Duster

[Dooglas]

Originally Posted by Boatyarddog

Question, did you paint over your shaft zinc?
Its not gonna work well like that.

That looks like blue 3M tape. The bottom paint appears to be black.

[Boatyarddog]

Originally Posted by Dooglas

That looks like blue 3M tape. The bottom paint appears to be black.

Ok, whew, my bad.
Thanks
SV Cloud Duster

[DaveSIM]

Davesim Did you check the prop strut to see if it has broken? It sounds to me like your clutch plate between engine and gearbox is about to fail. Switching from reverse to forward implies loose connection somewhere and the plate springs could be failing allowing excessive play as you shift. How is the stuffing box ? Nothing loose there? Keep us posted. Dave

[Cat36Mahalo]

Since you just changed the torque plate (damper plate) I suspect that the spline mesh up is sloppy. I’ve seen several complaints about poor splines on Hurth transmissions. Either live with it or pull the trans and check the play of the plate on the splines.

[motretu]

do you get the same symptoms going from forward to neutral to forward [assumes idle rpm]?

[Quadrille in JB]

Thanks for all of the replies
Yes, the engine mount nuts are tight
Yes, that’s blue tape over the zinc so I didn’t get it coated with prop speed, I removed the tape before splash
Yes, I replaced the torque plate and the splines were very tight. This was less than two hours run time ago
No, the strut is not broken. It’s very solid
Yes, it actually makes the noise when going from neutral to forward, we’re sailing this weekend and I just checked it out
I think it’s actually just a function of the three cylinder harmonic at lower rpm causing something to slap slap around this sounds like sheet metal clanking
Once it’s up to over 1500 RPM it runs like a sewing machine with no vibration
Unless someone comes up with a better idea I’ll just have to live with it
Thanks again
Bill

[DougR]

Maybe you need someone in the engine room while maneuvering from reverse to forward, etc. to try to pinpoint the location of the noise more closely......

Is the "clang" a one time noise, or does it occur continuously for 15 seconds? ie., clang,clang,clang, etc. metal on metal? Metal on rubber?

By the way, next time the prop is off, reinstall the prop with the thin nut on the shaft first, followed by the thick nut. This allows the more threads of the thick nut to take the load against the prop.

DougR

[Orion Jim]

Originally Posted by DougR

By the way, next time the prop is off, reinstall the prop with the thin nut on the shaft first, followed by the thick nut. This allows the more threads of the thick nut to take the load against the prop.

DougR

You are correct. It’s amazing how often they are installed incorrectly.

[Quadrille in JB]

I hadn’t thought of the thick nut going on first but it does make sense. But it probably doesn’t make a lot of difference with 25 horse power
I’ll try to take a video with sound of the clanging noise to see what everybody thinks. Have to get the Admiral to run the boat