Gearbox flange bolts

[Colin K]

Hello,
I wondered if anyone knew the imperial spec of the bolts used on my Fairline Corniche. TAMD41b engines MS4B box. The nuts/bolt head are 5/8. The bilge monster has stolen a couple of nuts and the bolts are not very pretty rusty one in the photo.

Cheers, Colin

 

[scottie]

Look up R&D coupling
Could be 7/16 unf should be nyloc and changed anyway if disturbed
Volvo would be either 8 or 10mm

 

[superheat6k]

Defo R&D

Brochure here - might help https://www.dropbox.com/s/w8rac6m9ubmv4ye/R and D Flexible Shaft Couplings.pdf?dl=0

 

[burgundyben]

The bolt top right looks newer, suggesting someone has been meddling previously.

Why has it come loose?

Bilge Monster eating nuts is mildy amusing, but the implications of that assembly failing at sea are serious.

 

[gery w]

I replaced the R&D couplings in my corniche, the new one came with stainless bolts.
I also considered leaving the R&D couplings out as I can’t see any benefits of having them.

 

[omega2]

Until you foul up then you will save a lot of money!!

 

[gery w]

R&D couplings are designed to fail safe, so wouldn’t help you in a prop foul situation?

 

[Seastoke]

Look up R&D coupling
Could be 7/16 unf should be nyloc and changed anyway if disturbed
Volvo would be either 8 or 10mm

looks to course for unf could be unc or wittworth

 

[Colin K]

Hello Chaps,
Thanks for the pointers yes it is a really course thread I confess the shiny bolt that you can just see is an M10 that I fitted courtesy of Screwfix I just used it to pull it all together as I was rebuilding her.
I tend to put a bit of thread lock on them when I do the final tighten up and never had one shake loose fingers crossed!!

I can confirm that the R+D couplings do not break if you get fouled. The reason that I am intimate with the transmission on my Corniche is due to me picking up a hefty rope five miles out of Ipswich last Summer and the first thing to go bang was the slip clutch on the gearbox (although it did not just slip it stripped the teeth off it ) " it blew up ha ha "
My bilge monster is a devote hoarder, Last weekend when the new box went in I had said shaft nuts lined up neatly like soldiers, Then kicked them into the bilge when I got into the engine bay to grunt the splines together so two nuts and two jubilee clips cannot be found presumed eaten. It is a bit of a worry as I also keep my "wife hidden" supply of pre mixed G+T's down there!!!
I guess really the main thing is to get the diameter of the bolt shaft right so will go armed with a micrometre next visit.

Once again thanks all. All the best Colin.

 

[superheat6k]

I remember intimately the bolts on the R&D coupling on my Turbo 36 were definitely a fine thread. These were a distinct advantage when I was using them to pull up the heavy plate I was using to get the coupling free of the shaft - a fine thread exerts a far higher pressure when used to force a bad via a bolt. I would suggest something like 1/2" UNF or possibly M12 Fine. One of the originals has a flat machined on to one of the bolt heads to check the alignment with.

 

[omega2]

Seen gearbox torn off the engine, because they did not fail, if none there then the whole power train would be a goner.

 

[Colin K]

Look up R&D coupling
Could be 7/16 unf should be nyloc and changed anyway if disturbed
Volvo would be either 8 or 10mm

Hello,
Well brought a bolt home so I could study it a bit closer easier than being upside down in the engine hatch!

Yup you got it right 7/16 and unf. (Fine thread). 3" long. Ordered a full set for both shafts bit horrified that i could spin the nut along the threads nyloc way past its best.

Cheers, Col.

 

[Amour]

Hi Colin hope all well glad to see getting box back in mine went back in boat last weekend . Roll on April to relaunch and test . Keeping an eye on your boat on web cam . We must try and meet up in the spring for a weekend cruise .

Gavin .