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Maudesmaster

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1 hour ago, frangar said:

It’s more usually referred to as the Recreational Craft Directive or RCD……

 

Not really. The regulations governing pre-2017 builds was called the Recreational Craft Directive or RCD, but to distinguish the far stricter regulations introduced in 2017 the name was changed to the Recreational Craft Regulations, so the difference is obvious.

 

But if you two want to continue spreading confusion between the two different sets of regulations, that's fine with me.

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6 hours ago, Maudesmaster said:

Thank you all I am presently awaiting a reply from Jonathan at T Norris and injector pump going to Gardner marine for overhaul 

Gardner Marine quoted me 1500 pounds recently for a pump and cambox overhaul, a rather eye watering price !  There are cheaper places to go.

 

Why are you opting to have this done when the issue may well be elsewhere? Is there another problem with the engine? The earlier post suggested the engine was responding OK. An optical tacho would confirm this.

Edited by jonesthenuke
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My family has two boats with 3LW's and 2:1 gearboxes one is is 50 ft the other 58ft  both are fitted with the same  prop as in the picture. They are 23" X 23" and as can be seen are are of a large blade area. Normal cruising revs are 500, max revs are 1000,  Almost never use anything over 750rpm. Boat stops within its own lengh in deep water.  Although you cannot fit 23" dia the nearer you can get will give you a good result.

 

Steven

Prop.jpg

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4 hours ago, Split Pin said:

My family has two boats with 3LW's and 2:1 gearboxes one is is 50 ft the other 58ft  both are fitted with the same  prop as in the picture. They are 23" X 23" and as can be seen are are of a large blade area. Normal cruising revs are 500, max revs are 1000,  Almost never use anything over 750rpm. Boat stops within its own lengh in deep water.  Although you cannot fit 23" dia the nearer you can get will give you a good result.

 

Steven

Prop.jpg

So much to consider I’m having the injector pump and sprayers  overhauled and calibrated and will refit next week 

I will check gear box oil although very hard to see level on the PRM stick and will re trial the boat and let you all know the results and go from there 

thank you for your input 

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46 minutes ago, Maudesmaster said:

So much to consider I’m having the injector pump and sprayers  overhauled and calibrated and will refit next week 

I will check gear box oil although very hard to see level on the PRM stick and will re trial the boat and let you all know the results and go from there 

thank you for your input 

 

You seem to be going to a helluvalot of trouble and having random expensive work done without ever diagnosing the cause.

 

I would suggest the following action before spending any serious cash:

 

1) Find the data plate on the gearbox and post here what the reduction ratio is.

2) Buy a cheapo ebay rev counter and measure the actual speed of the prop shaft at say 500rpm on the rev counter (Post it here.)

3) Dock the boat, clean the prop boss and read what size it is. Take lots of photos of the blade from various angles. Put the boat back in. Post the size here.

 

Once we have this info, some definitive advice is bound to be forthcoming. Do 1) and 2) first before shelling out £100 for the short docking. 

 

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7 hours ago, MtB said:

 

You seem to be going to a helluvalot of trouble and having random expensive work done without ever diagnosing the cause.

 

I would suggest the following action before spending any serious cash:

 

1) Find the data plate on the gearbox and post here what the reduction ratio is.

2) Buy a cheapo ebay rev counter and measure the actual speed of the prop shaft at say 500rpm on the rev counter (Post it here.)

3) Dock the boat, clean the prop boss and read what size it is. Take lots of photos of the blade from various angles. Put the boat back in. Post the size here.

 

Once we have this info, some definitive advice is bound to be forthcoming. Do 1) and 2) first before shelling out £100 for the short docking. 

 

And before you do 3), it should be possible to measure the approximate length of one propeller blade from the tip to the centre of the propshaft, through the weed hatch, and then double that to get the diameter. (Unless you don't have a weedhatch).

Edited by David Mack
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14 minutes ago, David Mack said:

And before you do 3), it should be possible to measure the approximate length of one propeller blade from the tip to the centre of the propshaft, through the weed hatch, and then double that to get the diameter. (Unless you don't have a weedhatch).

In his original post he says how big his prop is and how much space he has

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12 hours ago, MtB said:

 

You seem to be going to a helluvalot of trouble and having random expensive work done without ever diagnosing the cause.

 

I would suggest the following action before spending any serious cash:

 

1) Find the data plate on the gearbox and post here what the reduction ratio is.

2) Buy a cheapo ebay rev counter and measure the actual speed of the prop shaft at say 500rpm on the rev counter (Post it here.)

3) Dock the boat, clean the prop boss and read what size it is. Take lots of photos of the blade from various angles. Put the boat back in. Post the size here.

 

Once we have this info, some definitive advice is bound to be forthcoming. Do 1) and 2) first before shelling out £100 for the short docking. 

 

The gearbox is a new PRM 500 the prop is a new 21” x 18 the engine is a 3LW 

from a Folkestone fishing boat the injector pump and sprayers are being overhauled because of age, black smoke and leaking diesel from holes behind the levers 21AED740-D340-4DDC-AE15-E923A784375F.jpeg.10ddbdbee6ecec1612ff352658e0a29e.jpeg21AED740-D340-4DDC-AE15-E923A784375F.jpeg.10ddbdbee6ecec1612ff352658e0a29e.jpeg

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5 hours ago, Maudesmaster said:

The gearbox is a new PRM 500 the prop is a new 21” x 18 the engine is a 3LW 

What reduction is the gearbox? 

They come in four different ratios:

Model.     Ratio

500D1.5   1.459:1

500D2     1.935:1

500D2.5  2.565:1

500D3     2.904:1

 

A 500D3 will spin the prop at half the speed of a 500D1.5

 

With a 21x18 I would think that a  500D2 or a 500D1.5 would be required.

Edited by Loddon
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8 minutes ago, Loddon said:

What reduction is the gearbox? 

They come in four different ratios:

Model.     Ratio

500D1.5   1.459:1

500D2     1.935:1

500D2.5  2.565:1

500D3     2.904:1

 

A 500D3 will spin the prop at half the speed of a 500D1.5

 

With a 21x18 I would think that a  500D2 or a 500D1.5 would be required.

 

Thank you for expanding on why I am asking for the gearbox model number as stated on the gearbox data plate.

 

My money is on it turning out to be a 500D3, when with that blade it ought to be a D1.5. I'm not sure about the D500 but sometimes the reduction gears can be changed to a different ratio rather than having to replace the whole gearbox, should it turn out to be a 500D3. 

 

 

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I've played this game before😉

When I bought Parglena it had a D3 and was woefully under propped, swapped to a D2 and was over propped, got Crowthers to make me a matched prop and all was fine 😁

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Maybe a daft question - but - you have a left handed prop.

1) does your gearbox require a left handed prop ?

2) is your engine RH or LH rotation ?

 

And, remember that the 500 gear box can be set up to run RH or LH - is it set up for RH and you have put a LH prop on it ?

 

 

 

Screenshot (622).png

Edited by Alan de Enfield
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13 minutes ago, Loddon said:

I've played this game before😉

When I bought Parglena it had a D3 and was woefully under propped, swapped to a D2 and was over propped, got Crowthers to make me a matched prop and all was fine 😁

 

Me too!

 

The 21 x 18 blade in the photos is awfully close to the 21 x 19 on my own boat, which works great with a 1:1 final drive and Kelvin K1, revving to about 500rpm in deep water.

 

So I reckon the OP's slightly finer blade with a faster ticking over modern diesel like the Gardner will be fine with a 1.5 reduction.

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2 minutes ago, Alan de Enfield said:

Maybe a daft question - but -

1) does your gearbox require a left handed prop ?

2) is your engine RH or LH rotation ?

 

And, remember that the 500 gear box can be set up to run RH or LH - is it set up for RH and you have put a LH prop on it ?

 

 

 

Screenshot (622).png

 

If the op had the wrong prop then he would know because the boat would go backwards rather than going forwards slowly 😀

 

I believe that PRM boxes are happy in either direction so can take either hand of prop and the performance will be almost identical in either direction.

 

A very few engines rotate backwards and in this case the box needs adjusting (I think) so that its pump is working correctly. I don't think the 3LW is a backwards engine and PRM would not normally supply a box set backwards, but its worth checking. A tacho of some sort is also a very good idea.

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2 minutes ago, dmr said:

 

If the op had the wrong prop then he would know because the boat would go backwards rather than going forwards slowly 😀

 

I believe that PRM boxes are happy in either direction so can take either hand of prop and the performance will be almost identical in either direction.

 

A very few engines rotate backwards and in this case the box needs adjusting (I think) so that its pump is working correctly. I don't think the 3LW is a backwards engine and PRM would not normally supply a box set backwards, but its worth checking. A tacho of some sort is also a very good idea.

 

 

My suggestion was that maybe the gearbox is set up for RH rotation, the shaft is rotating RH but he has a LH propfi tted (hence the L marked on the prop) so he will be getting very poor perfomance and stopping power if the LH prop is turning in the 'wrong direction'.

 

It will be 'skidding' thru the water rather than 'screwing / pulling' thru water as the angles will be all-wrong.

 

Does the OP even know he has a LH rotation prop ?

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3 minutes ago, dmr said:

I believe that PRM boxes are happy in either direction so can take either hand of prop and the performance will be almost identical in either direction.

 

PRM state that their boxes can take full power in either rotation as the internal gearing is identical.  You just need to pull/push the gear selector the opposite way, usually by mounting the Morse cable to the opposite side.

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2 minutes ago, Alan de Enfield said:

My suggestion was that maybe the gearbox is set up for RH rotation, the shaft is rotating RH but he has a LH propfi tted (hence the L marked on the prop) so he will be getting very poor perfomance and stopping power if the LH prop is turning in the 'wrong direction'.

 

But as Dave points out, if an LH prop is turned the "wrong direction", the boat goes backwards (or stops). 

 

And as Mr Biscuits points out, PRM hydraulic boxes are symmetrical, they run either way and need setting to suit the prop hand. 

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5 minutes ago, Alan de Enfield said:

 

 

My suggestion was that maybe the gearbox is set up for RH rotation, the shaft is rotating RH but he has a LH propfi tted (hence the L marked on the prop) so he will be getting very poor perfomance and stopping power if the LH prop is turning in the 'wrong direction'.

 

It will be 'skidding' thru the water rather than 'screwing / pulling' thru water as the angles will be all-wrong.

 

Does the OP even know he has a LH rotation prop ?

If the OP has a LH prop rotating RH the boat will be going backwards. Surely the effect you describe could only arise if the prop was fitted back to front. And that could only happen if the manufacturer has bored the taper from the wrong end of the boss. Unlikely I think.

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5 minutes ago, TheBiscuits said:

 

PRM state that their boxes can take full power in either rotation as the internal gearing is identical.  You just need to pull/push the gear selector the opposite way, usually by mounting the Morse cable to the opposite side.

 

Yes, I said almost identical performance because (I think) in one direction the drive goes through an extra gear pair and a pedant might point out that a loaded gear mesh has marginally more loss than an unloaded mesh 😀

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3 minutes ago, David Mack said:

If the OP has a LH prop rotating RH the boat will be going backwards. Surely the effect you describe could only arise if the prop was fitted back to front. And that could only happen if the manufacturer has bored the taper from the wrong end of the boss. Unlikely I think.

 

Well they stamped it upside down, so it's possible ... :D

 

 

 

 

Edited by TheBiscuits
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Just now, David Mack said:

If the OP has a LH prop rotating RH the boat will be going backwards. Surely the effect you describe could only arise if the prop was fitted back to front. And that could only happen if the manufacturer has bored the taper from the wrong end of the boss. Unlikely I think.

 

Even then, no it couldn't. If you turn a fan blade (or propeller) around on it's shaft it still blows the same way if you think about it. (You will have turned the blades through 180 degrees.)

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