Crowthermarine Propellors

[buggsy]

Hi,

I have seen on the net that Crowther's produce very good props. I have asked them to advise on the correct prop for my engine and gearbox and i am considering changing my prop if they recommend a different spec. Has any member any experience of these or any other advice.

 

cheers,

 

Steve

[Gary Peacock]

Hi,

I have seen on the net that Crowther's produce very good props. I have asked them to advise on the correct prop for my engine and gearbox and i am considering changing my prop if they recommend a different spec. Has any member any experience of these or any other advice.

 

cheers,

 

Steve

 

 

They are probably the best in the game within the prices that the inland waterways brigade are prepared to pay.

[RobinJ]

Hi,

I have seen on the net that Crowther's produce very good props. I have asked them to advise on the correct prop for my engine and gearbox and i am considering changing my prop if they recommend a different spec. Has any member any experience of these or any other advice.

Never heard of them getting it wrong and always consider the economics.

[Chris Pink]

Hi,

I have seen on the net that Crowther's produce very good props. I have asked them to advise on the correct prop for my engine and gearbox and i am considering changing my prop if they recommend a different spec. Has any member any experience of these or any other advice.

 

cheers,

 

Steve

 

Could also try Norris of Isleworth for an alternative 'darn sarth'

[AlanH]

Hi,

I have seen on the net that Crowther's produce very good props. I have asked them to advise on the correct prop for my engine and gearbox and i am considering changing my prop if they recommend a different spec. Has any member any experience of these or any other advice.

I decided to change my prop recently and wanted a 15 X 9. I rang Crowthers and they quoted me £217 inc. VAT plus delivery with a four to six week wait. I decided that a 15 X10 would do as it was a common size and rang them again to ask if they had one in stock. They said that they'd get back to me but never did. I've heard from several sources that Crowthers props are prone to "singing" but I've no evidence of this.

TW Marine got me a 15 X 10 next day for £220 including the next day delivery charge and VAT. I believe this prop was made in the Phillipines but it looked/fitted/performs perfectly well.

[Mukiwa]

Hi,

I have seen on the net that Crowther's produce very good props. I have asked them to advise on the correct prop for my engine and gearbox and i am considering changing my prop if they recommend a different spec. Has any member any experience of these or any other advice.

 

cheers,

 

Steve

When my boat was stretched I spoke to them about my prop needs. The advice was excellent and their recommended 16x10 is spot on and I have no singing at all. I would not hesitate to recommend them.

[DHutch]

Ours is a crowther and we have been very happy with it.

- My grandad spec'ed it, drew out a load of charts and the works, talked to them who confirmed his workings, and we have been very happy.

 

Im sure there loads of other place to get props, maybe cheaper, or better, or both. But Crowther work too!

 

Ours is a 26*32" , oversquare, high dir , blade.

 

 

 

Daniel

[GUMPY]

I have changed the prop to a Crowther on ALL of my last 3 boats, there is no other make worth using as far as I am concerned and I have dealt with some of the others in the past.

 

Julian

Edited June 25, 2008 by idleness

[buggsy]

Hi,

I have seen on the net that Crowther's produce very good props. I have asked them to advise on the correct prop for my engine and gearbox and i am considering changing my prop if they recommend a different spec. Has any member any experience of these or any other advice.

 

cheers,

 

Steve

 

To follow on Crowthers have suggested that my 18 x 12 prop was ok for the original Lister STW3 but having replaced the engine with a Perkins D3.152 te correct prop should now be a 22 x14 !!!!!!!!! if i could physically fit it in. I am about to have the boat blacked so i can take some measurements. I should thick the engine will only be on tickover with this soze of prop.

 

thanks for the advice

 

Steve

[Liam]

How long is your boat?

 

Ours is 50ft with a Perkins D3.152 and that swings a 20 x 15 prop.

Edited June 26, 2008 by Liam

[alan_fincher]

How long is your boat?

 

Ours is 50ft with a Perkins D3.152 and that swings a 20 x 15 prop.

Don't forget that what reduction there is on the gearbox comes into play. Although you are comparing the same engine, it will only be valid to do so if both have a gearbox with the same reduction.

 

I did think that 22 x 14 sounded a lot, but perhaps the gearbox has a bigger reduction than some ?

[Liam]

Yes very true, ours is 2:1.

[Chris-B]

Baldock ( the boat) also runs a D3.152 with a 3.5 reduction setup

Our prop is a 26 x 22 3 blade 55% bar

and it does exactly what we want with a full length deep draft boat

 

But I have no idea whos prop it is as it was fitted by Foxton Boat Services back in the dark ages

 

Chris

[buggsy]

Don't forget that what reduction there is on the gearbox comes into play. Although you are comparing the same engine, it will only be valid to do so if both have a gearbox with the same reduction.

 

I did think that 22 x 14 sounded a lot, but perhaps the gearbox has a bigger reduction than some ?

 

Our boat is 60 foot and has a 160 VR PRM which from the manual states 2:1 reduction. I thought the recommended prop sounded big. With current prop the egine doesn't sound like it working that hard and i currently only cruise on canals and would say i am a pretty slow cruiser anyway. Would the bigger prop pull the stern down more.

 

Steve

[AlanH]

Our boat is 60 foot and has a 160 VR PRM which from the manual states 2:1 reduction. I thought the recommended prop sounded big. With current prop the egine doesn't sound like it working that hard and i currently only cruise on canals and would say i am a pretty slow cruiser anyway. Would the bigger prop pull the stern down more.

The bigger prop will make you go faster on tickover which is why I changed mine for a smaller one. If it is too big it will cause your engine to give out black smoke at max revs and will also reduce ther max attainable revs.

[John Orentas]

To follow on Crowthers have suggested that my 18 x 12 prop was ok for the original Lister STW3 but having replaced the engine with a Perkins D3.152 te correct prop should now be a 22 x14 !!!!!!!!! if i could physically fit it in. I am about to have the boat blacked so i can take some measurements. I should thick the engine will only be on tickover with this soze of prop.

 

thanks for the advice

 

Steve

 

 

Hi Steve.

 

I think you can do no more than accept the advice given by Crowthers but if your boat can't swing a 22" dia prop there are other things they can do, for example by increasing the percentage area (I can never remember the term) it is possible to reduce the diameter.

[alan_fincher]

Our boat is 60 foot and has a 160 VR PRM which from the manual states 2:1 reduction. I thought the recommended prop sounded big.

Well I'm certainly no propeller sizing expert.

 

But if it's only a 2:1 box, that sounds a big prop compared to others I have come across.

 

Years ago I had the Perkins P3-152, with a Parsons DF box, with a 2:1 reduction and that was propped with a 17" x 17".

 

That was about all it could swing, and it could have been a bit bigger, if there had been space, but I don't think it would have worked well with anything as big as 22".

 

Crowther's were aware they were sizing for a 2:1 reduction, weren't they ?

Edited June 26, 2008 by alan_fincher

[DHutch]

Hi Steve.

 

I think you can do no more than accept the advice given by Crowthers but if your boat can't swing a 22" dia prop there are other things they can do, for example by increasing the percentage area (I can never remember the term) it is possible to reduce the diameter.

Ive heard people used a mix of terms, blade area is usally given as a ratio of the total area given by the nominal diameter as i understand it often called the 'disk-area ratio' or DAR.

 

- As you say, if you are forced to decrease the diameter, you can count it by upping the area, and also increasing the pitch.

- What your fight is prop-slip as im sure you know, increasing the area helps reduce it, increasing the pitch helps reverse the affect of it once its occured!

 

 

Hence a a 20 x 15 prop and 22 x 14 prop are proberbly more simular than you might think, without knowing the blade area of them.

And why oversquare (pitch greater than diameter) props are usally very high area ratios, sometimes even greater than one.

 

 

 

Daniel

[Blackdog]

I was talking to someone at a boat yard a while ago on this subject. I,ve got a JD3 on a 1.93 gearbox turning a 20 by 20 prop. I was looking at changing the prop as the engine is very lightly loaded. Got no room to go larger in diameter so I was thinking of going for an increase in pitch. The guy at the boat yard said they had a similar problem and they fitted a 4 bladed prop, he said it worked well. Has anyone got a 4 bladed prop or should I go for a pitch change.

[Liam]

The only 4 bladed prop I've heard of (and seen) is on the Leeds Liverpool boat Ambush which is powered by a 4cyl Gardner.

 

It used to have a 2cyl Gardner and he regrets swapping it now.

[onthecut]

Hi all.

 

Crowthers --- my experience with them is a 10 / 10 rating. Highly competent, work done to time, friendly and approachable. Wouldn't hesitate to recommend them.

 

 

Mike.

[buggsy]

Some further questions.

 

I have been speaking to a local boat yard and they recommend "under propping" so that the engine works harder to avoid glazing of the pots.

 

What does the term singing prop actually mean and how do you avoid it.

 

Crowther's recommend 22 x 14 but would there be any benefit from going from 18 x 12 to say 20 x 14?

 

Whats the best way to measure the depth of the skeg whilst the boat is in the water?

 

cheers,

 

Steve

[johnthebridge]

Some further questions.

 

I have been speaking to a local boat yard and they recommend "under propping" so that the engine works harder to avoid glazing of the pots.

 

What does the term singing prop actually mean and how do you avoid it.

 

Crowther's recommend 22 x 14 but would there be any benefit from going from 18 x 12 to say 20 x 14?

 

Whats the best way to measure the depth of the skeg whilst the boat is in the water?

 

cheers,

 

Steve

1)Can't agree with the first point-under propping will only allow the engine to run faster. Over propping will make the engine slog, and usually work harder. This is (arguably) more likely to lessen glazing of the bores.

2)Singing prop is an expression that's not fully understood, but it's likely to be related to cavitation or slippage. If it is, then you'll have to play with the prop size to get rid of it, but it isn't in itself a particular problem, merely an aggravation.

3) Probably not. Crowthers recommendations are usually pretty accurate.

4)Unless you're familiar with the shape of the skeg on your boat, it's going to be difficult. Obviously you can gain a good idea of the draught of your boat by measuring the inside of the hull at the stern, but if the skeg "hangs" down (admittedly unlikely on a modern boat) then you cannot say for certain. Why do you want this measurement?

[buggsy]

1)Can't agree with the first point-under propping will only allow the engine to run faster. Over propping will make the engine slog, and usually work harder. This is (arguably) more likely to lessen glazing of the bores.

2)Singing prop is an expression that's not fully understood, but it's likely to be related to cavitation or slippage. If it is, then you'll have to play with the prop size to get rid of it, but it isn't in itself a particular problem, merely an aggravation.

3) Probably not. Crowthers recommendations are usually pretty accurate.

4)Unless you're familiar with the shape of the skeg on your boat, it's going to be difficult. Obviously you can gain a good idea of the draught of your boat by measuring the inside of the hull at the stern, but if the skeg "hangs" down (admittedly unlikely on a modern boat) then you cannot say for certain. Why do you want this measurement?

 

 

Thanks John for the replies. I was asking about the measuring to see if i can actually fit the larger prop.

 

cheers,

 

steve

[steelaway]

Thanks John for the replies. I was asking about the measuring to see if i can actually fit the larger prop.

 

cheers,

 

steve

 

Hi There

 

You should be able to measure down to the skeg through the weedhatch, the bottom of the weedhatch is the top of the swim.

Also remember to leave enough room to allow the prop to clear itself of any debri.

I dont think any one on here agrees with me, but my theory is that the cruising speed should be within the max torque of the engines rpm.

 

Alex