a couple of Volvo questions

[colhel]

I've just started the Winter work on our Nimbus with a TAMD41A engine.
I may have found the cause of an ongoing issue that has been with the boat since we bought her in August this year where very occasionally, when i first accelerate away there's a kind of rubbing scraping noise, I just throttle back quickly, start again and all is well again. The drive shaft can just be seen through the clamp in the coupling and this is scored quite badly, so I think this could well be the cause, so to rectify I'll need a new shaft and maybe a coupling. I this is the cause is it possible for the shaft to slide out of the coupling, I'm thinking if the shaft is being worn away it could become loose in the coupling, or is there a secondary means the shaft is likely to be secured by? I moved the boat to Weymouth from her home berth in East Cowes so could get a lift out in Portland but ideally I'd like to have lifted and anti fouled in summer back on the Isle of Wight but on the way home I had visions of the shaft dropping out the back.
I've also started work on the cooling system as I've had a couple of impellors go and thanks to our good friend Andy (Andy59 0n here) the seal on the water strainer has been diagnosed as the main culprit, hence it's likely I'll have bits of rubber where don't want them. So I've started to dissmantle and remove the heat exchager and noticed a couple of anomalies, when I drained the gearbox water it was clear, but when I drained the turbo it was red with coolant. I topped up the coolant with plain water before leaving Cowes for Weymouth so the engine was running at a steady 3000 rpm with the temperature gauge reading normal. I'm guessing stray bits of rubber in the system?

Cheers

Col

 

[Plum]

I've just started the Winter work on our Nimbus with a TAMD41A engine.
I may have found the cause of an ongoing issue that has been with the boat since we bought her in August this year where very occasionally, when i first accelerate away there's a kind of rubbing scraping noise, I just throttle back quickly, start again and all is well again. The drive shaft can just be seen through the clamp in the coupling and this is scored quite badly, so I think this could well be the cause, so to rectify I'll need a new shaft and maybe a coupling. I this is the cause is it possible for the shaft to slide out of the coupling, I'm thinking if the shaft is being worn away it could become loose in the coupling, or is there a secondary means the shaft is likely to be secured by? I moved the boat to Weymouth from her home berth in East Cowes so could get a lift out in Portland but ideally I'd like to have lifted and anti fouled in summer back on the Isle of Wight but on the way home I had visions of the shaft dropping out the back.
I've also started work on the cooling system as I've had a couple of impellors go and thanks to our good friend Andy (Andy59 0n here) the seal on the water strainer has been diagnosed as the main culprit, hence it's likely I'll have bits of rubber where don't want them. So I've started to dissmantle and remove the heat exchager and noticed a couple of anomalies, when I drained the gearbox water it was clear, but when I drained the turbo it was red with coolant. I topped up the coolant with plain water before leaving Cowes for Weymouth so the engine was running at a steady 3000 rpm with the temperature gauge reading normal. I'm guessing stray bits of rubber in the system?

Cheers

Col

I am assuming you do not have an outdrive. A shaft coupling that relies on clamp pressure only is not uncommon but obviously, assuming it is of the correct specification for your boat, the clamp bolts have to be tightened correctly. Yes, if there is no other fastening then the shaft could slide out in reverse (until the prop hits the rudder) or it could slide forward enough to bind the coupling or the prop against the cutlass bearing which will do damage but not sink the boat. Put a felt tip pen mark on the shaft and one adjacent on the coupling. Go for a short blast and see if there is any relative movement.

The gearbox cooler has seawater in it so should be clear. The turbo has coolant in it so should be coolant colour (green if using VP coolant). You should drain thd fresh water and replace with correct spec coolant asap in case we suddenly get freezing temperatures although the coolant also is a corrosion inhibitor.

Having had two impeller failures (assuming when you removed them there were bits of vanes unaccounted-for) then yes you need to find them (in the main heat exchanger) but as your running temperature is normal there is no great priority.

Www.solocoastalsailing.co.uk

 

[colhel]

Thank You Plum, very useful (and reassuring)
The coolant has been in since pre purchase and as it's obviously loosing fresh water from somewhere I think the systems due a service.
No doubt more questions to follow

 

[oldgit]

Thank You Plum, very useful (and reassuring)
The coolant has been in since pre purchase and as it's obviously loosing fresh water from somewhere I think the systems due a service.
No doubt more questions to follow

Shaft may also be secured in the coupling by a roll pin and might be tapered.
Pin could be hidden by coats of paint.
Will need to be drifted out before shaft can be withdrawn.
Good idea to change oil in gearbox as well.
Also check cutlass bearing, new one only around £50.00.
Which gearbox.
Is it the notorious VP MS4 or something more reliable such as Velvet Drive 72.

 

[colhel]

Thanks OG.
The coupling Flange is like this one https://www.marinepartseurope.com/en/volvo-penta-explodedview-7745630-90-19647B.aspx
On mine there is a stainless cap head screw in the middle level with the centre of the bore which I guessed could be securing a pin or key, however assuming the shaft is spinning in the bore, it must be broke. I couldn't tell if it's tapered, but thinking about it that clamp would have to be extremely tight if there was no key or tape.
If you click on the link below (still can't post pics properly) you'll see a photo of the gearbox. I'm assuming the stainless cheese head is the dipstick, is there a another drain somewhere, or do I have to pump it out through the top? Incidentally, said screw is extremely tight and as yet I've not been able to undo it. There is an Allen head to the rear and wondered if I could drain and fill from this.

https://photos.google.com/u/1/photo/AF1QipPQHhm8oLrEGlr5ymPbxlIlE-0L9SuM9WKT8DKE

 

[scottie]

As others have said it’s a clamp type coupling which should have at least a pinch screw which locate the shaft both fore and aft and axially
This can be simply a shallow hole drilled into the shaft allowing the screw to locate and stop relative movement.
Other methods include drilling through the shaft at 90deg or preferably across the edge of the shaft as in a cycle cotter pin which is preferable as it does not reduce the strength if the shaft.
As old git says it can be parallel or tapered.
You are not likely to have the shaft drop out whilst you have 150plus horses pushing it forward but a quick burst astern could be embarrassing!
There are several options available as you but all will depend on what you find when you strip the shaft ranging from tightening the clamping bolts and fitting a scecuring screw to replacing the lot including machining the existing shaft to enable using a slightly smaller coupling either split or solid with or without a key so worth having a look at both R&D and VP catalogs but it’s all basically simple engineering.

 

[Plum]

Thanks OG.
The coupling Flange is like this one https://www.marinepartseurope.com/en/volvo-penta-explodedview-7745630-90-19647B.aspx
On mine there is a stainless cap head screw in the middle level with the centre of the bore which I guessed could be securing a pin or key, however assuming the shaft is spinning in the bore, it must be broke. I couldn't tell if it's tapered, but thinking about it that clamp would have to be extremely tight if there was no key or tape.
If you click on the link below (still can't post pics properly) you'll see a photo of the gearbox. I'm assuming the stainless cheese head is the dipstick, is there a another drain somewhere, or do I have to pump it out through the top? Incidentally, said screw is extremely tight and as yet I've not been able to undo it. There is an Allen head to the rear and wondered if I could drain and fill from this.

https://photos.google.com/u/1/photo/AF1QipPQHhm8oLrEGlr5ymPbxlIlE-0L9SuM9WKT8DKE

Unfortunately your link to the gearbox picture does not work for me. The coupling you refer to does not have the cross drilling. Those couplings, and some other makes too, rely solely on the clamping to retain the shaft. Nothing wrong with that if you have the correct matching undamaged shaft and the bolts/screws are tightened to the specified torque. You still need to establish if that coupling is slipping or not before you do anything as you still don't know if this is the cause of your symptoms.

Www.solocoastalsailing.co.uk

 

[colhel]

A picture of the gearbox. Thanks for all your help so far.

https://photos.app.goo.gl/Gsh257R5VJNz6hUc6