Engine size !! Advice please.

[chip]

Hi, Thanks all contributers for a brill forum, I have used this site many times over the past few months whilst I have been working on my sailaway and have now come to a point where I need to ask a question re my choice of engine.

The boat is a 57'' Piper Semi Trad with a 17 - 10 prop, and I am going to fit a Vetus Engine. Vetus have said they think their 33 hp engine would be ok but I was thinking of fitting their larger 44 hp but still use my exsisting prop. Is this a wise thing to do?

I am concerned that in the future when I sell the boat the engine size ie 33 hp may put people off. Would this be the case?

Any input would be greatly appreciated.

Thanks

Chip

[Chris J W]

If it helps, I've a 43hp Beta in a Wilson trad. Not entirely sure about the prop size, but I'd guess at about 20-24 inch.

[Billypownall]

Hi, Thanks all contributers for a brill forum, I have used this site many times over the past few months whilst I have been working on my sailaway and have now come to a point where I need to ask a question re my choice of engine.

The boat is a 57'' Piper Semi Trad with a 17 - 10 prop, and I am going to fit a Vetus Engine. Vetus have said they think their 33 hp engine would be ok but I was thinking of fitting their larger 44 hp but still use my exsisting prop. Is this a wise thing to do?

I am concerned that in the future when I sell the boat the engine size ie 33 hp may put people off. Would this be the case?

Any input would be greatly appreciated.

Thanks

Chip

If you are going to fit a Vetus why not go for the 42h.p. We have this unit in a 57' with the 17" x 10" prop. Seems an ideal match. The 38 h.p. unit would be OK but I think 33 h.p. will leave you underpowered

[PeterF]

Agree with above comments, our boat is 55ft with 40hp, think the prop is 17 x 10 (but not entirely sure) and the engine seems a good fit for the boat size including doing river work.

Edited January 20, 2008 by PeterF

[Timleech]

If you are going to fit a Vetus why not go for the 42h.p. We have this unit in a 57' with the 17" x 10" prop. Seems an ideal match. The 38 h.p. unit would be OK but I think 33 h.p. will leave you underpowered

 

I would have thought that the 33hp would be plenty if it will swing a 17" prop. Can you get it with a 3:1 gearbox?

 

There are those who aren't keen on the Technodrive/Twindisc gearbox, I couldn't possibly comment

 

Tim

[Gary Peacock]

33hp is a bit small these days I would go with a 40-45HP and a good matched prop.

 

Get the prop from somewhere like Crowther Marine and they will match it to the boat engine and gearbox for you.

 

Don't listen to the experts in their own imagination types in your marina etc advice you how to spend your money on the right prop go to someone who does it for a living.

Edited January 20, 2008 by Gary Peacock

[bottle]

Hi Chip and welcome.

 

I understand that you are having a different make of engine but HP is HP

 

Have a look here Beta Marine, it is a PDF document that gives a guide to engine and prop sizing

[Chris-B]

33hp is a bit small these days I would go with a 40-45HP and a good matched prop.

 

Get the prop from somewhere like Crowther Marine and they will match it to the boat engine and gearbox for you.

 

Don't listen to the experts in their own imagination types in your marina etc advice you how to spend your money on the right prop go to someone who does it for a living.

 

 

Wholeheartedly seconded Gary !!!

[Timleech]

Hi Chip and welcome.

 

I understand that you are having a different make of engine but HP is HP

 

 

...except that prop size has a large bearing on efficiency and especially manouvering.

 

Having had a quick look at what Vetus offer, they can supply a Technodrive with 2.5:1 ratio, or a ZF with 2.63:1. Either of these ought to run a 'better size' prop if you have room for it (probably about 18" but talk to the prop experts about that), which should mean the 33hp is more than adequate.

 

Tim

[steelaway]

Hi, Thanks all contributers for a brill forum, I have used this site many times over the past few months whilst I have been working on my sailaway and have now come to a point where I need to ask a question re my choice of engine.

The boat is a 57'' Piper Semi Trad with a 17 - 10 prop, and I am going to fit a Vetus Engine. Vetus have said they think their 33 hp engine would be ok but I was thinking of fitting their larger 44 hp but still use my exsisting prop. Is this a wise thing to do?

I am concerned that in the future when I sell the boat the engine size ie 33 hp may put people off. Would this be the case?

Any input would be greatly appreciated.

Thanks

Chip

 

Hi There

Have a look here - discussed in detail last week

http://www.canalworld.net/forums/index.php...c=12543&hl=

Alex

[chip]

Thanks all for help, so it seems as though I will go for larger engine ( I will alter order details tomorrow and maybe have it with me wed ).

 

RE the prop is it possible to change that through the weed hatch? The boat is already in the water and I hope to drop the engine in whilst it is floating too. Never fit one before so it may turn around and bite me.

Cheers

[steelaway]

Thanks all for help, so it seems as though I will go for larger engine ( I will alter order details tomorrow and maybe have it with me wed ).

 

RE the prop is it possible to change that through the weed hatch? The boat is already in the water and I hope to drop the engine in whilst it is floating too. Never fit one before so it may turn around and bite me.

Cheers

Yes you can change the prop through the weed hatch, I have done it twice.

It will necessary to have the drive shaft connected to the engine.

Remove the split pin - remove the nut and washer - turn the prop until you have the key & keyway at the top - mark this position on the drive shaft inside the engine bay. Replace the nut a couple of turns - now you need a wedge to drive between the hull bearing and the prop. I have used a mooring pin - the prop is on a taper and the shock of an hammer blow should loosen it. As soon as you break the taper the prop will be loose. tie a rope around the prop and secure it to something in the boat. Remove the nut and making sure the keyway is at the top and slide of the prop, remove the key.

After the replacement of the new prop, the major problem in changing the prop through the weed hatch is finding the hole for the split pin, if it in a castle nut it is easy - if it is drilled through the nut you may have problems. You may have to buy or make a castle nut.

Good luck

Alex

[chip]

Yes you can change the prop through the weed hatch, I have done it twice.

It will necessary to have the drive shaft connected to the engine.

Remove the split pin - remove the nut and washer - turn the prop until you have the key & keyway at the top - mark this position on the drive shaft inside the engine bay. Replace the nut a couple of turns - now you need a wedge to drive between the hull bearing and the prop. I have used a mooring pin - the prop is on a taper and the shock of an hammer blow should loosen it. As soon as you break the taper the prop will be loose. tie a rope around the prop and secure it to something in the boat. Remove the nut and making sure the keyway is at the top and slide of the prop, remove the key.

After the replacement of the new prop, the major problem in changing the prop through the weed hatch is finding the hole for the split pin, if it in a castle nut it is easy - if it is drilled through the nut you may have problems. You may have to buy or make a castle nut.

Good luck

Alex

Brill, thanks alex. best get some spare split pins then.

Where are u in shardlow, Rons?

[steelaway]

Brill, thanks alex. best get some spare split pins then.

Where are u in shardlow, Rons?

 

Hi Rons

Not at Shardlow at the moment I had to leave my boat on the River Lea in London for a while.

You shouldn't need more split pins. My method of finding the hole was to feel with a terminal screw driver - about the diameter, but if you can't get it lined up contact me and I will make you a castle nut.

Alex

[chip]

Hi Rons

Not at Shardlow at the moment I had to leave my boat on the River Lea in London for a while.

You shouldn't need more split pins. My method of finding the hole was to feel with a terminal screw driver - about the diameter, but if you can't get it lined up contact me and I will make you a castle nut.

Alex

Cheers

I was refering to Ron Grundy, thanks for offer.

[Tony Brooks]

Hi, Thanks all contributers for a brill forum, I have used this site many times over the past few months whilst I have been working on my sailaway and have now come to a point where I need to ask a question re my choice of engine.

The boat is a 57'' Piper Semi Trad with a 17 - 10 prop, and I am going to fit a Vetus Engine. Vetus have said they think their 33 hp engine would be ok but I was thinking of fitting their larger 44 hp but still use my exsisting prop. Is this a wise thing to do?

I am concerned that in the future when I sell the boat the engine size ie 33 hp may put people off. Would this be the case?

Any input would be greatly appreciated.

Thanks

Chip

 

 

Please look back through the threads for info on the Technodrive gearbox that Vetus tend to use. Please also note that Vetus state very short "running out of gear times" for their engines (unlike Beta with who I have no connection).

 

In my view verbal statements I received from Vetus plus written documentation severely questions any CE marking they give their engines for INLAND (not estuary or seagoing) use. I feel they do not meet the suitability for purpose requirement.

 

I know there are hundreds of Vetus engines out there but I am sure there are better choices.

[Timleech]

Please look back through the threads for info on the Technodrive gearbox that Vetus tend to use. Please also note that Vetus state very short "running out of gear times" for their engines (unlike Beta with who I have no connection).

 

In my view verbal statements I received from Vetus plus written documentation severely questions any CE marking they give their engines for INLAND (not estuary or seagoing) use. I feel they do not meet the suitability for purpose requirement.

 

I know there are hundreds of Vetus engines out there but I am sure there are better choices.

 

Tony

 

I've tried to drop gentle hints about the Technodrive box in this thread, but Vetus do offer other boxes including the PRM 150 (for more money, of course). The Mitsubishi base engine is IMO a pretty good unit (apart from the frequency of oil changes needed )

 

Tim

[blackrose]

According to the Beta guide my 57' x 12' (28 - 30 tonne) widebeam is well underpowered as she only has an Izusu 55hp engine. However, I've never found there to be a lack of power - even turning into the ebb tide on the Thames to enter the Limehouse basin was ok.

 

I have a PRM 150 gearbox and a 19" x 13" prop. The smallprint at the top of the Beta guide mentions reducing prop pitch to achieve maximum rpm. How does this work and are there any advantages to having a longer prop pitch like mine?

Edited January 21, 2008 by blackrose

[Timleech]

According to the Beta guide my 57' x 12' (28 - 30 tonne) widebeam is well underpowered as she only has an Izusu 55hp engine. However, I've never found there to be a lack of power - even turning into the ebb tide on the Thames to enter the Limehouse basin was ok.

 

I have a PRM 150 gearbox and a 19" x 13" prop. The smallprint at the top of the Beta guide mentions reducing prop pitch to achieve maximum rpm. How does this work and are there any advantages to having a longer prop pitch like mine?

 

My interpretation is that their recommended prop size for IW use is slightly oversize, presumably based on what gives best results in practice, balancing things such as comfortable cruising revs etc. This does mean that the engine won't be able to produce its full rated power, so if you *need* the full rated power you need to go to a smaller prop. Bear in mind that this doesn't necessarily mean that you will have any more effective 'manouvring power'.

 

Tim

[Timleech]

I know there are hundreds of Vetus engines out there but I am sure there are better choices.

 

Might just be worth looking at the Thonycroft versions of Mitsubishi, such as

 

http://www.thornycroftengines.co.uk/type95.htm

 

Tim

[Yoda]

Simple rule. Widebeams that mostly move short distances need manuvering power from the engine therefore a prop that allows all the power from the engine. narrow boats need cruising efficiency and need to be overproped. The prop should be sized by the sfc curve of the engine.

[Keeping Up]

Simple rule. Widebeams that mostly move short distances need manuvering power from the engine therefore a prop that allows all the power from the engine. narrow boats need cruising efficiency and need to be overproped. The prop should be sized by the sfc curve of the engine.

I disagree

[blackrose]

I disagree

 

Good, because I still don't understand!

 

Are we saying that within a certain range appropriate for the engine size, big props = more manouvearability but less power than small props? Could a bigger prop offer less revs but more torque/rev perhaps?

 

And what about the pitch, where does that come into it?

Edited January 21, 2008 by blackrose

[Yoda]

I disagree

 

Ok Allan you can but the statement that for maximum efficiency the prop needs to be sized for rpm in the sfc curve still holds true.

[Keeping Up]

Ok Allan you can but the statement that for maximum efficiency the prop needs to be sized for rpm in the sfc curve still holds true.

Yes I agree with that statement 100%. However the very minor inefficiencies that result from setting things up diferently are usually far outweighed by other considerations for canal-based narrowboats.

• Most narrowboats have engines that are more powerful than they require for canal use. If that engine is over-propped, the slowest attainable speed of travel is usually too fast.
  
• Under-propping generally means that the engine has a reserve of power available to enable it to turn the propellor at a reasonable speed even when it has a bundle of old rope and plastic bags wrapped around it.
  
• Under-propping corresponds to an increase in engine revs which will often allow faster battery-charging at slow speeds.
  
• Excessive over-propping may limit the engine revs and prevent it from reaching its maximum revs or delivering its maximum power.