Sr2 engine electrics upgrade - A127 alternator and VSR

[Spoonman]

My boat has a SR2 MGR2 engine and its original  lucas 11ac 45amp alternator thats on the blink and outdated engine electrics.

 

I have been advised on this forum that a 70 - 75 amp A127 style alternator  would be a suitable upgrade  alongside installing a more simple VSR charging system.

 

What factors do i need to take in to consideration when arranging this?

 

. Would the current fan belt ,camshaft pully/alternator pulley be suitable to just install the A127 ,or would more modifications be needed accomodate it?

Some are being described as "marine" versions (insulated terminals?) , others being sold for use on cars? 

 

In regards to the VSR system, i have seen some reasonably priced  "split charge kits" online , where the relay is rated a certain number of amps. Would the vsr need to be "matched" closely to the alternator output (alongside output from solar panels ?) or would say a 140 amp vsr be suitable for any amp output that was under that amount .

 

I have attached some screen shots of potential products I've seen and was wondering if these would be suitable for my purpose

 

Any links to suitable products would be greatly appreciated.

 

[WotEver]

2 minutes ago, Spoonman said:

would say a 140 amp vsr be suitable for any amp output that was under that amount .

Yes, this

[bizzard]

There is usually plenty of room to fit different alternators on the SR2. If you have plenty of adjustment on the alternators slotted bar the old drive belt will probably fit ok as long as the alt pulley groove matches the old one, a notched belt is best.  Again I will mention. Do you have the large diameter alternator drive pulley on the camshaft 10-12'', and not the standard industrial 7'' one.

[BEngo]

Things to watch:

Can you mount the new alternator with the pulley in the same plane as the camshaft pulley? If not belt wear will be high.

Are the old and new belt sizes the same? 

Will the new pulley ratio be enough to get an adequate output from the new alternator?   The SR camshaft will only go up to about 600 rpm, flat out.  So with a 4 to 1 pulley ratio you will not see more than 2400 alternator rpm. Mostly it will be less.  

 

N

 

[OldGoat]

44 minutes ago, BEngo said:

Things to watch:

Can you mount the new alternator with the pulley in the same plane as the camshaft pulley? If not belt wear will be high.

Are the old and new belt sizes the same? 

Will the new pulley ratio be enough to get an adequate output from the new alternator?   The SR camshaft will only go up to about 600 rpm, flat out.  So with a 4 to 1 pulley ratio you will not see more than 2400 alternator rpm. Mostly it will be less.  

 

N

 

Aye - and there's the rub - alternators need to rotate fast to generate any reasonable output and teh only ay for old Listers is a complicated arrangement of pulleys and lay shafts - not very practical. Sorry.

[nicknorman]

Also you should check the rotational direction. Does the camshaft on an SR2 go opposite direction to normal? (Not sure). Rotational direction of the alternator is important for the fan to work properly. Some alternators have a bidirectional fan but the one in you picture looks handed.

[dor]

Is a VSR of any benefit over a conventional relay if there is only one alternator?

[Tony Brooks]

9 minutes ago, dor said:

Is a VSR of any benefit over a conventional relay if there is only one alternator?

Yes, it won't energise while starting unless you have solar charging. If you do have solar it will also charge both banks.

 

@Spoonman make sure you alter the main  alternator charging lead goes to the DOMESTIC battery bank and connect the relay to sense from that bank.

[Spoonman]

52 minutes ago, nicknorman said:

Also you should check the rotational direction. Does the camshaft on an SR2 go opposite direction to normal? (Not sure). Rotational direction of the alternator is important for the fan to work properly. Some alternators have a bidirectional fan but the one in you picture looks handed.

I believe it is normal clockwise rotation ,as  anticlockwise SR's have a letter A  after the engine type?  Looking from the stern end of my boat the fly wheel goes clockwise 

[Tony Brooks]

So the camshaft that drives the alternator on those engines may well turn anticlockwise. Please check unless you get an alternator with a bidirectional/universal fan.

[Tracy D'arth]

17 minutes ago, Spoonman said:

I believe it is normal clockwise rotation ,as  anticlockwise SR's have a letter A  after the engine type?  Looking from the stern end of my boat the fly wheel goes clockwise 

Check that, it sounds odd. Flywheel is not the pulley for the alternator.

[PhilR]

50 minutes ago, Tracy D'arth said:

Check that, it sounds odd. Flywheel is not the pulley for the alternator.

Viewed from the FRONT of the engine standard rotation of the crankshaft is anti-clockwise . The pulley for the alternator, and the starting handle, fit on the camshaft extension.  The camshaft is gear driven from the crankshaft, so the camshaft rotates clockwise (viewed from the front). The reduction box reverses the rotation so the standard prop is left- handed.

 

Edited August 7, 2020 by PhilR

[Spoonman]

1 hour ago, Tony Brooks said:

So the camshaft that drives the alternator on those engines may well turn anticlockwise. Please check unless you get an alternator with a bidirectional/universal fan.

 

47 minutes ago, Tracy D'arth said:

Check that, it sounds odd. Flywheel is not the pulley for the alternator.

 

Ahh ok i misunderstood. On the attached picture the red arrow is the direction the fan belt rotates .

[Tracy D'arth]

8 minutes ago, PhilR said:

Viewed from the front of the engine standard rotation of the crankshaft is anti-clockwise. The pulley for the alternator and the starting handle fit on the camshaft extension.  The camshaft is gear driven from the crankshaft, so the camshaft rotates clockwise.

That's what I remembered, the OP has it A about F?   Not if the alternator runs the opposite way from the conventional. He needs a counterclockwise alternator. He is correct, the engine runs conventionally clockwise from the front so the cam and alternator run counter clock.

Edited August 7, 2020 by Tracy D'arth

[Spoonman]

3 hours ago, bizzard said:

  Do you have the large diameter alternator drive pulley on the camshaft 10-12'', and not the standard industrial 7'' one.

This is something i will need to check , but i will assume it is the standard as little has been changed n to this engine in a long time. So increasing the size of this will increase the pulley ratio between the one on the alternator and the one in the camshaft, and lead to a higher rpm for the alternator?

 

3 hours ago, BEngo said:

the SR camshaft will only go up to about 600 rpm, flat out.  So with a 4 to 1 pulley ratio you will not see more than 2400 alternator rpm. Mostly it will be less.  

 

[Sir Nibble]

You want the cheaper car alternator. If you have an anti clockwise or bi-directional fan on your existing alternator you can fit that but will need someone to take the 15mm shaft hole in the centre out to 17mm. I will have a look and see if I have a suitable fan just in case.

[Sir Nibble]

Bit of a shitstorm has descended on me so I've not had chance for a proper look. I shall sort something out Monday. Check that the new alternator comes with a pulley, if not I can find that too.

[Spoonman]

I've uploaded some pictures.

On 07/08/2020 at 11:36, bizzard said:

There is usually plenty of room to fit different alternators on the SR2. If you have plenty of adjustment on the alternators slotted bar the old drive belt will probably fit ok as long as the alt pulley groove matches the old one, a notched belt is best.  Again I will mention. Do you have the large diameter alternator drive pulley on the camshaft 10-12'', and not the standard industrial 7'' one.

 

The pulley on the engine is approximately 8in diameter, but I'm not sure if there would be room to add a bigger one in the current position that the alternator bar and cam shaft pulley are in.

 

The belt is a 6226MC.

 

I would be looking for a right hand fixings on the  alternator?

Edited August 9, 2020 by Spoonman

[Tracy D'arth]

Leece Neville Prestolite  90 amp alternators come as universal mounting, will do left and right. remember you need a reverse or no matter fan.

90 to 100 amps is the max on a single v belt.

[Steve56]

On 07/08/2020 at 19:37, Spoonman said:

I believe it is normal clockwise rotation ,as  anticlockwise SR's have a letter A  after the engine type?  Looking from the stern end of my boat the fly wheel goes clockwise 

That is correct. The letter A denotes anti clockwise rotation. So your engine will be clockwise rotation.Therefore the alternator drive from the camshaft will also be clockwise rotation.

[Steve56]

Just for information as there seems to be some confusion. The std SR engine for marine use is clockwise rotation . This is always rotation of the flywheel when looking from behind. If it was anti clockwise rotation it would have a letter A in the number, but very rare for a marine engine. Therefore if standard rotation ( clockwise) the camshaft will also be running in a clockwise rotation.

[Tony Brooks]

9 minutes ago, Steve56 said:

That is correct. The letter A denotes anti clockwise rotation. So your engine will be clockwise rotation.Therefore the alternator drive from the camshaft will also be clockwise rotation.

I must be thick or something. I was not aware that Listers had an idler gear in the cam shaft  drive so the camshaft will go the opposite way to the crankshaft - do they use an idler

Edited August 9, 2020 by Tony Brooks

[Steve56]

Exactly. If you look at the flywheel from the rear of the engine it will be turning clockwise. If you look at the camshaft from the front of the engine it will also be turning clockwise.

[Tracy D'arth]

21 minutes ago, Steve56 said:

That is correct. The letter A denotes anti clockwise rotation. So your engine will be clockwise rotation.Therefore the alternator drive from the camshaft will also be clockwise rotation.

Sorry, I think that is incorrect.

13 minutes ago, Steve56 said:

Just for information as there seems to be some confusion. The std SR engine for marine use is clockwise rotation . This is always rotation of the flywheel when looking from behind. If it was anti clockwise rotation it would have a letter A in the number, but very rare for a marine engine. Therefore if standard rotation ( clockwise) the camshaft will also be running in a clockwise rotation.

Now I am really confused I always look at the front of an engine, crank pulley if it had one and surely this is a clockwise rotating engine as most are?

 

EDIT Listers seem to agree with you,   http://listerparts.co.uk/SR.html

 

I never realised that!!! But the camshaft rotates in the opposite if its gear driven?  Yet the OP marked his photo as running the other way.

 

Hopelessly confused, we need clarification.

Edited August 9, 2020 by Tracy D'arth

[Steve56]

4 minutes ago, Tracy D'arth said:

Sorry, I think that is incorrect.

Now I am really confused I always look at the front of an engine, crank pulley if it had one and surely this is a clockwise rotating engine as most are?

Lister always quote engine rotation as looking at the flywheel. As you are looking at the camshaft it is also turning clockwise.