Right or left handed propellor identification...

[Timleech]

A fine question... I will ask brother. I wasn't on the boat when he and the engine chap started it. It will be even more Monty Python if it works perfectly forwards after all this panic. I cannot imagine two engine minded boys would be wrong when puzzling it over together, but stranger things have happened at sea....

 

An alternative (if the problem is real and not imagined) might be to change the reduction gearbox for a standard 2-wheel type. You would need to catch one first, though.

There might also be a slight difference in the 'drop' from engine to output coupling.

 

Tim

[alan_fincher]

The standard Petter manual for the AV2 says......

 

The standard rotation is clockwise when looking from the driving shaft end when looking at Marks I, III & V and anti-clockwise when looking from the driving shaft end when looking at Marks II and IV.

 

Engines with reverse rotation can also be supplied if specially requested.

 

So I would say, on balance, that helps not one iota!

[boatymum]

This is making my head go round in circles too....

 

I have just spoken to the engine vendor who was very obliging and went off to check another similar engine there. He has just tried that one and it needs a R/H prop too. He says if you look at the flywheel from the front, if it goes clockwise, then its a R/H prop and vice versa.

 

He remembers that it had a reduction box on it which changes the direction.

 

Very soon we will have to have a boat party and all come and see.

Edited January 9, 2013 by boatymum

[alan_fincher]

I have just spoken to the engine vendor who was very obliging and went off to check another similar engine there. He has just tried that one and it needs a R/H prop too. He says if you look at the flywheel from the front, if it goes clockwise, then its a R/H prop and vice versa.

Sorry, but being pedantic, looking at the rotation of the engine flywheel can only tell you the rotation of the engine, and not necessarily what prop it requires.

 

As I think you are already quite clear on, the gearbox may either preserve the rotation of the engine, and turn the prop the same way, or it may reverse it, so that an engine turning one way causes the prop to turn the other, (all assuming forward gear).

[sociable_hermit]

I have just spoken to the engine vendor who was very obliging and went off to check another similar engine there. He has just tried that one and it needs a R/H prop too. He says if you look at the flywheel from the front, if it goes clockwise, then its a R/H prop and vice versa.

 

He remembers that it had a reduction box on it which changes the direction.

I think you need to be VERY careful with the terminology here.

 

By the sounds of it, what he's saying is that the flywheel on yours spins clockwise, thus the propshaft and prop would normally spin clockwise in forward gear. However he also recalls that it has a reduction prop which changes the direction, so in actual fact the prop will spin anti-clockwise with the engine and gearbox in forward gear.

 

I would run that exact explanation past him and check that's what he means.

 

I'd also check which way the flywheel spins in reality, rather than relying on the world of theory.

[bizzard]

A couple of checks to do.

Almost certainly the gear lever pushed forward will be forward gear. Put a chalk mark say on the engines flywheel ringgear inline with any bit of the engines casting or nut or bolt and mark this with chalk too.

Now go to the gearbox output propshaft half coupling and put a chalk mark on this also aligning the mark with another mark on again say a bit of casting or nut on that reduction gear casing. Flip the engines decompressor levers so the engine turns easily.

Now watch your chalk marks and start turning the engine flywheel in its ''CORRECT NORMAL running direction''. That gearbox is possibly 3.1 reduction so for every 3 times the flywheels chalk marks pass each other the prop half coupling will only rotate once so the chalk mark on the half coupling will go round once and stop at its other mark.

If 2,1 reduction which I doubt the engines flywheel will rotate twice for every one turn of the propshaft half coupling.

Whatever the difference in revolutions between the flywheel and the g/box output coupling is is your reduction gear-ratio.

At the same time note in which direction the gearbox output prop coupling rotates in relation to the flywheel.

Both these checks will determine the gearboxes reduction ratio and the direction the prop turns, ''left or right hand prop needed''.

The pitch of the propeller blades to match the reduction ratio, engine power ect ect is another matter.

Edited January 9, 2013 by bizzard

[Timleech]

This is making my head go round in circles too....

 

I have just spoken to the engine vendor who was very obliging and went off to check another similar engine there. He has just tried that one and it needs a R/H prop too. He says if you look at the flywheel from the front, if it goes clockwise, then its a R/H prop and vice versa.

 

He remembers that it had a reduction box on it which changes the direction.

 

Very soon we will have to have a boat party and all come and see.

 

The 'other similar engine' probably doesn't have the unusual 3-wheel reduction, so it's prop will (probably) go the opposite way to yours.

If he really has another similar engine to hand, it could easily be the other one of a pair, with opposite handed props. AV2 Petter marine engines are not very common today, so if he had two of them that seems to me to be a reasonable scenario.

 

Edit - don't get confused between Bizzard's 3:1 reduction and my suggestion of a 3-wheel reduction. Totally different aspects of the gearbox, can be either, both or neither

 

Tim

Edited January 9, 2013 by Timleech

[boatymum]

I will send all that chalking info to my brother and we will see.

 

In the meantime, I have invited the propellor vendor to come and have a look at this discussion and we are most likely going to order a left hand propellor anyway as it is sounding like we need one. If we need the leftie on the boat, we will then have a righty to sell and that shouldn't be hard. If we don't need the new leftie, he may let me return it if it is undamaged. The boat was only supposed to be staying over the hols and gone by the 6th of Jan so we are now at the mercy of the marina.

 

Thank you everyone for being so helpful.

Edited January 9, 2013 by boatymum

[Chris Pink]

A fine question... I will ask brother. I wasn't on the boat when he and the engine chap started it. It will be even more Monty Python if it works perfectly forwards after all this panic. I cannot imagine two engine minded boys would be wrong when puzzling it over together, but stranger things have happened at sea....

 

OK, unthreading the information;

 

the boat is in the water, your brother and a mechanic started it and said "it's got the wrong prop on it".

 

Is this right?

 

if so, it does sound like you need a LH propellor.

 

You don't need to worry about any of the mechanical intricacies (I'm not trying to be patronising, honest ;-) all you need to know is "which way does the boat go when you move the gear lever forward"

 

forward: propellor is right

back: propellor is wrong and, as from Post #2 it's a RH one so you need a LH one and the engine supplier gave you the wrong information.

 

if it is going to cost a lot to replace then there are ways of mitigating that cost.

[bizzard]

I will send all that chalking info to my brother and we will see.

 

In the meantime, I have invited the propellor vendor to come and have a look at this discussion and we are most likely going to order a left hand propellor anyway as it is sounding like we need one. If we need the leftie on the boat, we will then have a righty to sell and that shouldn't be hard. If we don't need the new leftie, he may let me return it if it is undamaged. The boat was only supposed to be staying over the hols and gone by the 6th of Jan so we are now at the mercy of the marina.

 

Thank you everyone for being so helpful.

If you carry out my simple chalk checks to the letter you will be ''certain'' of the correct direction prop needed and the gear-ratio.

[RLWP]

<snip>

 

You don't need to worry about any of the mechanical intricacies (I'm not trying to be patronising, honest ;-) all you need to know is "which way does the boat go when you move the gear lever forward"

 

forward: propellor is right

back: propellor is wrong and, as from Post #2 it's a RH one so you need a LH one and the engine supplier gave you the wrong information.

 

if it is going to cost a lot to replace then there are ways of mitigating that cost.

 

 

If you carry out my simple chalk checks to the letter you will be ''certain'' of the correct direction prop needed and the gear-ratio.

 

Yes, but Chris's test is more certain

 

Richard

[boatymum]

I will do them all..... I'm grateful for all advice.

 

If the boat isn't going to go forwards when we want it to then the replacement prop and fitting costs just have to be absorbed. What a complete waste of money though. We saw the engine working when we picked it up but we weren't buying the prop at the time just listening to the nice 'put put put' noise and considering the price etc etc. If only we had bought a prop off the engine vendor at the time. But 'if onlys' have to be forgotten.... not a way forward. As a greenie I just took all advice at face value. Most seasoned boatys would know these things without thinking. But now we are one more step to being seasoned by experience.... Onwards and hopefully forward soon.....

Edited January 10, 2013 by boatymum

[bizzard]

Yes, but Chris's test is more certain

 

Richard

Ah yes Richard I thought the boat was still out of the water, not read all the posts.

[BEngo]

 

 

The nice thing is that apparently the engine sounds wonderful. Unfortunately this is going to be hugely expensive to put right. Apparently the boat has to be lifted out of the water again which involves full crane costs plus labour. That blows the entire budget for any windows. We shall have to paint them on!!!

 

 

It is quite possible to change the prop without having to take the boat out of the water or hire a crane. I have done it a few times and have posted details on here before of the method, but you do need a bit of spare propshaft and sufficient depth of water to get the rudder out. PM me if you would like the instructions.

 

 

The prop you currently have should be re-saleable, unless its some sort of weird size, and the supplier may well exchange it for a LH replacement less a re-stocking charge.

 

N

 

PS where is the boat?

Edited January 9, 2013 by BEngo

[ditchcrawler]

If the boat is in the water have you tried running the engine and pushing the gear leaver forward. If so which way does it go? If its forward it's fine, stop erring, if backwards its wrong.

You seam to be worrying about what people tell you things should be.

[twbm]

 

.... I was tearing my hair out before finding this forum. Nothing was making any sense....

 

That's also the opposite way round as it happens.

[sociable_hermit]

OK, unthreading the information;

 

the boat is in the water, your brother and a mechanic started it and said "it's got the wrong prop on it".

 

Is this right?

 

if so, it does sound like you need a LH propellor.

 

You don't need to worry about any of the mechanical intricacies (I'm not trying to be patronising, honest ;-) all you need to know is "which way does the boat go when you move the gear lever forward"

 

EXCEPT we do need to establish for definite that the gearbox is in its normal 'forward' running position when the boat is going forward. As others have said, the gearbox won't like running in back gear as its normal setting, which might be the engine + gearbox + control linkage + prop combination that would currently give forward motion with a LH prop.

 

I know that's a bit unlikely but gearbox repairs don't tend to be cheap or easy, so best to get it right if possible.

[Chris Pink]

how many gearboxes have you come across where you move the lever back to go forward and forward to go back? KIS

[Timleech]

how many gearboxes have you come across where you move the lever back to go forward and forward to go back? KIS

 

That's a bog standard Newage (BMC) mechanical box, apart from the possible 3-wheel reduction, and yes the Ahead position of the lever is forward as you would expect.

 

Tim

[sociable_hermit]

That's a bog standard Newage (BMC) mechanical box, apart from the possible 3-wheel reduction, and yes the Ahead position of the lever is forward as you would expect.

 

Tim

Is it possible to get the lever on the gearbox opposite to the operating handle, though? For example if it's mechanically linked, rather than a cable?

 

If not, then I agree with Chris Pink - if it works, it works.

 

However your post earlier gave the impression that it might be possible to end up with the gearbox running back to front as its default when the boat was going forwards. It's one thing doing that deliberately knowing it is wrong, quite another to get to that position by accident.

[bizzard]

The extra gear wheel in the reduction unit looks as if it is the same size as the gearboxes output gearwheel so just reversing the rotation and not altering the gear-ratio, so was possibly intended for use on a twin screw boat where its mate on another engine and gearox didn't have the extra wheel to allow the props to contra-rotate.

[Timleech]

The extra gear wheel in the reduction unit looks as if it is the same size as the gearboxes output gearwheel so just reversing the rotation and not altering the gear-ratio, so was possibly intended for use on a twin screw boat where its mate on another engine and gearox didn't have the extra wheel to allow the props to contra-rotate.

 

..erm..

 

I think I said that ages ago...

 

Tim

 

Is it possible to get the lever on the gearbox opposite to the operating handle, though? For example if it's mechanically linked, rather than a cable?

 

If not, then I agree with Chris Pink - if it works, it works.

 

However your post earlier gave the impression that it might be possible to end up with the gearbox running back to front as its default when the boat was going forwards. It's one thing doing that deliberately knowing it is wrong, quite another to get to that position by accident.

 

I'm not sure how you work that out, I've just re-read my own posts, but my apologies if that impression was obtainable.

 

Tim

[RLWP]

Is it possible to get the lever on the gearbox opposite to the operating handle, though? For example if it's mechanically linked, rather than a cable?

 

If not, then I agree with Chris Pink - if it works, it works.

 

However your post earlier gave the impression that it might be possible to end up with the gearbox running back to front as its default when the boat was going forwards. It's one thing doing that deliberately knowing it is wrong, quite another to get to that position by accident.

 

You (and Bizzard) are getting confused.

 

 

The operating lever shown is in the standard place, just with a long lever and a rubber hand grip. Forwards is forwards.

 

On the back of the gearbox is this:

 

 

This is a version of the reduction gear on the back of the gearbox.

 

Normally, in this casing, there would be a small gear on the top meshing with a big gear on the output shaft, giving a reduction in speed, increase in torque and reversing the rotation of the shaft relative to the engine.

 

In this case (hah!), there is an additional gear in the bulge circled. This means that the output shaft will now go the same way around as the engine. So, by having two identical engines, with two identical gearboxes, you can fit one two wheel reduction box to one, and a three wheel reduction box to the other. In forward, one propeller goes one way round, the other propeller goes the other way around. One shaft gets a left handed prop, the other gets a right handed prop, the boat goes forward on both engines BUT the prop-walk is eliminated

 

Does that help?

 

Richard

Edited January 9, 2013 by RLWP

[bizzard]

You (and Bizzard) are getting confused.

 

 

The operating lever shown is in the standard place, just with a long lever and a rubber hand grip. Forwards is forwards.

 

On the back of the gearbox is this:

 

 

This is a version of the reduction gear on the back of the gearbox.

 

Normally, in this casing, there would be a small gear on the top meshing with a big gear on the output shaft, giving a reduction in speed, increase in torque and reversing the rotation of the shaft relative to the engine.

 

In this case (hah!), there is an additional gear in the bulge circled. This means that the output shaft will now go the same way around as the engine. So, by having two identical engines, with two identical gearboxes, you can fit one two wheel reduction box to one, and a three wheel reduction box to the other. In forward, one propeller goes one way round, the other propeller goes the other way around. One shaft gets a left handed prop, the other gets a right handed prop, the boat goes forward on both engines BUT the prop-walk is eliminated

 

Does that help?

 

Richard

I'm not confused, i've had several boats in the past with mechanical gearboxes ie Gray marine, Paragon, Coventry and Lister. And have already said that when the gearlever is pushed forward it should put the box into fore-gear.

[boatymum]

Update

 

Brother did flywheel test and it is a 2:1 and propshaft goes backwards. He says he and the engine chap had engine in forwards and boat went backwards, and in reverse it went forwards. His words:- From behind, engine clock, prop anti.

 

There really isn't much doubt left that we have a cack handed engine one way or another....!

 

The two marina men know their Petters and Listers inside out so they are going to fix the problem. They also say that the engine has been mounted on flexible mounts which is wrong for an old engine like that. I feel they know exactly what they are doing so I shall be ordering that other prop.\

 

You guys have been so nice to a newbie. I'm still not sure I quite understand prop-erly....

 

I promise to tell you when we are able to move forwards.

Edited January 10, 2013 by boatymum