V-Drive Coupling Bolt - Help, Please

[theway]

I found this bolt under the engine, and it looks to go into the end of the coupling on the end. It fits well, but doesnt thread easily into the hole. I put it in once, and tightened it a bit, but not all the way because there was some resistance to threading/screwing. It has fallen out again and im wondering if anyone has a good solution and knows what this bolt does. Any help is appreciated




Im fairly new to engines

thanks
austin

[SkiprJohn]

Sorry I can't help with that one but there are others here more familiar with v-drives. They'll post soon I hope.
Is your shaft on the other side of the v-drive and under the engine and is there another coupling under the engine?
I'd check (by mirror or feel) all other places where a bolt might have come out before proceeding too much further. It appears to be the same size as coupling bolts.
kind regards,

[Hillbillyfunk]

take a piece of string, tie the bolt to something nearby, if bad things happen put the bolt in the hole, if nothing bad is happening now, leave the bolt on the string

[Laidback]

Austin
Please supply Make & Model of Engine

[never monday]

looks like a Yanmar

OP,
No bolts go in the center hole of the coupler. It may go in a hole on the outside circumference. After looking again. See the hole 90 deg from the end hole. Try that one.

[delmarrey]

I'd take a wild guess and say it's a 'stop bolt' for the end of the prop shaft. Also one of the set screws that holds the shaft in place is missing (That hole on the side of the coupler).

[perchance]

I am inclined to agree with delmarrey in that it looks like a keeper bolt that threads into the end of the prop shaft. If the threads are tight get a tap and chase out the threads and use thread locker when you re install it. If the threads on the bolt are distorted or worn in any way don't reuse it.

[delmarrey]

Originally Posted by perchance

I am inclined to agree with delmarrey in that it looks like a keeper bolt that threads into the end of the prop shaft. If the threads are tight get a tap and chase out the threads and use thread locker when you re install it. If the threads on the bolt are distorted or worn in any way don't reuse it.

If it were a keeper bolt the coupler would not be threaded. It could be really rusty making it look like the coupler has threads.

I would pull the coupler to find out for sure!

It's the wrong kind of bolt to be the set screw unless someone not knowing the difference installed a bolt instead.

[perchance]

The coupler is not threaded, the prop shaft is. Kind of a belt and suspenders approach used in conjunction with set screws. The set screw may not be missing just recessed out of sight.

[ShipShape]

It looks like it has a separate washer - every significant bolt on my Yanmar is a numbered, flanged hex. Delmarrey's idea of a stop bolt seems plausible, but that application would not use a washer.

It may be a bolt from some other part of the boat that just rolled into the bilge and everybody before you was too lazy to retrieve it. When I cleaned my bilge there was quite the assortment of fasteners and "things". I cleaned them all and kept them until I figured out their origin - only one bolt was missing from the engine. Other items from the engine apparently got in the bilge because of mechanics using the bilge as a disposal area.

[Chief Engineer]

I would take a look at the bolts in the coupling.....There might be a "newer" bolt in there. As it has a washer on it....it is not a bolt that goes into the coupler to secure the shaft.

Check over the transmission/bellhousing and where the engine mount attach to the engine.

Believe me, would be amazed at the amount of detritus you find under old engines.

I find it funny that this alleged Yanmar is Painted Universal Bronze/copper

[perchance]

This is my thoughts on this. The output shaft of the vee drive is hollow allowing the prop shaft to project through it. The shaft coupling is keyed to the shaft and the coupling is bolted to it. The bolt in hand appears to have come from the hole in the end of the coupling as there appears to be clean metal in the hole. This is just my opinion but I could be wrong.

[Chief Engineer]

What you are showing in the picture is not a vee-drive.

It is an offset drive

[capngeo]

Originally Posted by Chief Engineer

What you are showing in the picture is not a vee-drive.

It is an offset drive

CE: I was just going to say that and you beat me with your edit!

To the OP: It appears as others mentioned it "keeps" the shaft under reverse thrust... and as others said you are missing at least one set screw. Inasmuch as the shaft is likely frozen into the coupling never to come out without much fuss and fanfare, Murphy's law dictates it WILL pull out at the least opportune moment.

My advise? Get someone who is mechanically inclined to chase threads as required and replace the missing fasteners. Use a thread locker or safety wire to retain them afterwards.

[theway]

Wow, thank for all the replies, i was busy looking at other forums...

I have place the screw back in and tightened it as much as possible, there is resistance before it gets all the way in. The bolt still falls out. I have been using the engine for about 4hrs today and all seems well.

The engine is a yanmar 30g and the shaft does run back under the engine.

It doesnt go in the hole 90 degrees on the site, ther is already a hex in there.

This is the end of the coupler (looking) piece, there was old white paint on the piece, and on the bold, and there are clear threads inside the hole, so im sure the bolt goes here, it just wont tighten all the way, and come out when i use the engine, i am single handing, so its hard to watch the engine and have it in gear.






Thank you all, any more thoughts with the new images?