Propellors

[peterboat]

My boat is in dry dock being blasted and zingered, I have fixed the leaking stern tube and insert, and at the same time I have sorted out the prop issue the boat is a 57 x 12 widebeam with wheelhouse that weighs about 30 tonnes, it should have had a Barrus Shire 65 in it but on investigation Little brown mouse rogered the first owner and put a 50 hp in it they also fitted a prop 19 x 14 which was to big for it, it would only rev to 2000 rpm. So today I went to Woodwards in Hull to have it sorted so what size do you folks think I ended up with

 

Peter

[GUMPY]

19x12 or possibly 17x14

Assuming 2:1 reduction

Edited July 9, 2015 by Loddon

[peterboat]

I thought 19 x 12 but I was wrong that would have been right for a 65hp, and the 19 x 14 would have been right for the boat pre stretch and with a 65hp. Very complicated these props.. So I have ended up with a 19 x 10 they repitched my prop straightened it out balanced and polished it cant wait to try it just to see if the puter got it right

 

Peter

[zenataomm]

It took them several runs at it to get the blades right on the QEII ...... probably didn't have 'pooters back then for that sort of thing, so probably did it quicker

[GUMPY]

I've got a 19x14 on my 50hp Beta in a 60ft narrowboat, revs to 2300 and does 7mph but then the underwater shape is a bit special for a modern boat.

I would have thought 50hp would be a tad light for a big boat, we had 110 in a 60ftx11'6 barge and that was just nice with a 23x16 .

[PaulG]

with wheelhouse that weighs about 30 tonnes.....

Get a lighter wheelhouse?

[bargemast]

Get a lighter wheelhouse?

 

Didn't know lighters had wheelhouses, and are they not as heavy then ?

 

Peter.

[PaulG]

 

Didn't know lighters had wheelhouses, and are they not as heavy then ?

 

Peter.

[peterboat]

I've got a 19x14 on my 50hp Beta in a 60ft narrowboat, revs to 2300 and does 7mph but then the underwater shape is a bit special for a modern boat.

I would have thought 50hp would be a tad light for a big boat, we had 110 in a 60ftx11'6 barge and that was just nice with a 23x16 .

It is a tad light it was supposed to be a 65hp in a 50 foot widebeam which would have been ok but little brown mouse cheated and fitted a 50hp but still did all paperwork for a 65. when I stretched it 7 foot I had no idea it had the wrong engine in it. So now a few years down the line I have to sort it out which hopefully this prop will do

[magnetman]

It is a tad light it was supposed to be a 65hp in a 50 foot widebeam which would have been ok but little brown mouse cheated and fitted a 50hp but still did all paperwork for a 65. when I stretched it 7 foot I had no idea it had the wrong engine in it. So now a few years down the line I have to sort it out which hopefully this prop will do

Good luck with that

 

I've got a Beta 90 (original unit was a Perkins M90 which I replaced with an equivalent in terms of power/torque) in my 58x12' barge which is about 30-35 tonnes. This is ample power with a very comfortable reserve. My boat is a Pickwell and Arnold which have an unusual underwater shape and are very easily driven (very long swims and 45' chines rather than slab sides). I could manage with 70hp (modern unit) but would not want much less in that size boat really. Can't rememBer my prop size but its just right.

 

I hope the new prop does help but I also feel that a (modern unit revving to 2500/2800rpm with 2:1 box) 50hp engine is somewhat underpowered unless the boat is only ever used on canals.

 

My 2p

[peterboat]

Good luck with that

 

I've got a Beta 90 (original unit was a Perkins M90 which I replaced with an equivalent in terms of power/torque) in my 58x12' barge which is about 30-35 tonnes. This is ample power with a very comfortable reserve. My boat is a Pickwell and Arnold which have an unusual underwater shape and are very easily driven (very long swims and 45' chines rather than slab sides). I could manage with 70hp (modern unit) but would not want much less in that size boat really. Can't rememBer my prop size but its just right.

 

I hope the new prop does help but I also feel that a (modern unit revving to 2500/2800rpm with 2:1 box) 50hp engine is somewhat underpowered unless the boat is only ever used on canals.

 

My 2p

Its hard to dump an engine when it has very low hours on it the new prop should allow it to give its full 50 hp at 3000rpm, so for the most I am on canals but we do go on the Trent where its lack of revs has been a problem so we will see what we see. I have thought of putting a small turbo on it to up its power a bit and also clean up the emissions, but that is after I have tried this fix. The boat is a Johnathon Wilson shell and the swim is very long in fact with the old prop in still water tickover was to fast so hopefully it will be easier to park up

 

Peter

[magnetman]

If you can get the full revs out of it then maybe its ok. Hopefully it'll go (and stop!) Nicely

 

Not sure about retrofitting a turbo - that would be an interesting project !

[peterboat]

They used to have 20 - 30 hp listers in sheffield size boats and they went up and down the trent fully loaded so I really do have my fingers crossed for a good result, who would have thought props are rocket science

 

Peter

[Tony Dunkley]

They used to have 20 - 30 hp listers in sheffield size boats and they went up and down the trent fully loaded so I really do have my fingers crossed for a good result, who would have thought props are rocket science

 

Peter

 

That's very true, but it must be remembered that there were two things in their favour that modern pleasure craft rarely have.

One was a large diameter, slow revving propeller . . . . 27'' to 28'' diameter and 500-600 rpm maximum . . . . . . very much more efficient at converting horsepower into propulsive thrust than todays small diameter high revving jobs.

The second great advantage was that these boats were in the charge of experienced rivermen who knew how to work tides.

Woodwards will have provided you with the best that can be achieved given the limitations in performance and efficiency that come with slow displacement hulls that can't accommodate a respectably sized propellor because of their shallow draught. The lighter pitch will allow your engine to rev to it's full rated power output, but there will be a small price to pay in terms of slightly reduced efficiency at those increased revs.

A small propeller turning at 1500 rpm is never going to give great performance on a slow displacement vessel, so don't expect too much.

Edited July 11, 2015 by Tony Dunkley

[Dalslandia]

 

That's very true, but it must be remembered that there were two things in their favour that modern pleasure craft rarely have.

One was a large diameter, slow revving propeller . . . . 27'' to 28'' diameter and 500-600 rpm maximum . . . . . . very much more efficient at converting horsepower into propulsive thrust than todays small diameter high revving jobs.

The second great advantage was that these boats were in the charge of experienced rivermen who knew how to work tides.

Woodwards will have provided you with the best that can be achieved given the limitations in performance and efficiency that come with slow displacement hulls that can't accommodate a respectably sized propellor because of their shallow draught. The lighter pitch will allow your engine to rev to it's full rated power output, but there will be a small price to pay in terms of slightly reduced efficiency at those increased revs.

A small propeller turning at 1500 rpm is never going to give great performance on a slow displacement vessel, so don't expect too much.

 

Very Correct, something to Think about, if there is room for a bigger prop, use a higher gear ratio, like 3 or 4 to one. And a bigger correctly sized propeller.

[blackrose]

My boat is in dry dock being blasted and zingered, I have fixed the leaking stern tube and insert, and at the same time I have sorted out the prop issue the boat is a 57 x 12 widebeam with wheelhouse that weighs about 30 tonnes, it should have had a Barrus Shire 65 in it but on investigation Little brown mouse rogered the first owner and put a 50 hp in it they also fitted a prop 19 x 14 which was to big for it, it would only rev to 2000 rpm. So today I went to Woodwards in Hull to have it sorted so what size do you folks think I ended up with

 

Peter

I have the same size boat with an Isuzu 55, PRM 150 (2.09:1 reduction ratio) and had my prop repitched from 19 x13 to 18.5 x 11.5. It used to only rev to 1950rpm and now revs to 2200, so only another 250rpm but a lot more power.

 

Norris said they could reduce the pitch further if I wanted but were reluctant to make the prop too flat as it would have no "bite". I wonder if 10" is too flat?

 

I will be interested in the results.

Edited July 12, 2015 by blackrose

[blackrose]

Good luck with that

 

I've got a Beta 90 (original unit was a Perkins M90 which I replaced with an equivalent in terms of power/torque) in my 58x12' barge which is about 30-35 tonnes. This is ample power with a very comfortable reserve. My boat is a Pickwell and Arnold which have an unusual underwater shape and are very easily driven (very long swims and 45' chines rather than slab sides). I could manage with 70hp (modern unit) but would not want much less in that size boat really. Can't rememBer my prop size but its just right.

 

I hope the new prop does help but I also feel that a (modern unit revving to 2500/2800rpm with 2:1 box) 50hp engine is somewhat underpowered unless the boat is only ever used on canals.

 

My 2p

It certainly will help...

 

The pilot who took my boat across the Bristol channel told me my boat had plenty of power and was happy because we made the crossing in good time. He said that whatever combination of engine, gearbox and prop I had was well matched. This was after the prop repitch.

 

About 3 years ago I had a burn up on the Thames with a friend of mine who has the same Liverpool widebeam with a 70hp Isuzu. We were neck and neck for about half a mile until we both had to slow down. This was before the prop repitch.

 

Big engines are often redundant on displacement craft due to the hull speed of the boat. That will be its main limitation. The most important thing is to make sure the engine, gearbox and prop are well-suited to each other.

Edited July 12, 2015 by blackrose

[magnetman]

I like being able to get the boat where I want it with very little revving up and minimal bother

Not at all concerned about racing anyone Or time trials (which I would win anyway ) but I really do like a bit of low end torque for maneuvering. It makes a big difference in my experience.

 

Edit to do something

Edited July 12, 2015 by magnetman

[magnetman]

I am guessing the op boat may have a bowthruster which will help a little bit for maneuvering but I would rather a boat with a large torquey engine (and a boat shaped underwater section) and no bowthruster than a smaller less torquey engine with a girlie button.

 

Personal preference

[Tony Dunkley]

It certainly will help...

 

The pilot who took my boat across the Bristol channel told me my boat had plenty of power and was happy because we made the crossing in good time. He said that whatever combination of engine, gearbox and prop I had was well matched. This was after the prop repitch.

 

About 3 years ago I had a burn up on the Thames with a friend of mine who has the same Liverpool widebeam with a 70hp Isuzu. We were neck and neck for about half a mile until we both had to slow down. This was before the prop repitch.

 

Big engines are often redundant on displacement craft due to the hull speed of the boat. That will be its main limitation. The most important thing is to make sure the engine, gearbox and prop are well-suited to each other.

 

You need to bear in mind that this complimentary pilot was probably comparing your boats' performance with that of similar badly designed and shaped hulls with comparably inefficient propellers.

[Dalslandia]

Dalslandia have a 32"X26" 3 blade propeller, a 3:1 SCG gearbox, and a 11 liter 6 cylinder Scania, 163 HP, and a very usefull bowthruster of 11 kW, 400 mm tube.

[peterboat]

I am guessing the op boat may have a bowthruster which will help a little bit for maneuvering but I would rather a boat with a large torquey engine (and a boat shaped underwater section) and no bowthruster than a smaller less torquey engine with a girlie button.

 

Personal preference

No bowthruster and no need of it to be honest I was taught to boat by a trent/shefield boatman and his lessons have helped me no end over the years I am looking forward to trying it out on thursday night so will report on how good or poor it is

 

Peter

[magnetman]

Do let us know as in my opinion this is quite an interesting topic. Very boaty.

[peterboat]

For a change it is and nothing negative. For me I am trying to make the best of a bad job I have the wrong engine but that shouldnt stop me making the boat safer on strong flowing rivers

 

Peter

[peterboat]

Hi all boat back in water engine now pulls to 3000 rpm si right on the button for max power cruises at 1600 and still stops ok big plus is it will now go slow so expensive zinga doesnt get damaged perfik

 

Peter