NarrowBoat engine conversion

[TheCandleBoat]

Hi everyone this is my first post here.

 

I have a 1982 50ft skillcraft NarrowBoat with a BMC 1500 engine in it.

 

Recently the BMC is becoming increasingly unreliable and has a large amount of piston slap in the block.

It does not smoke but takes a stupid amount of heating cranking and more heating to get it to start and it tends to run on three cylinders out of four until it gets rather high on the revs.  I have done a compression test. There is almost no compression in cylinder 1 but the rest seem ok.

This engine was rebuilt 3 years ago by calcutt boats who I believe are the BMC experts.

After all the hassle of keeping my BMC running I have decided to remove it and install a Lister HR3 in an engine room rather then an engine bay since my boat is ripped out to a shell and I am doing a self fit out.

 

My plans are to have the bedroom at the back of the boat and have the engine room directly after my bedroom then my bathroom and then kitchen and living area. 

 

To install my HR3 I understand that it requires good strong steel bearers for it to live on.

 

My boats baseplate is 5mm thick and I am thinking I am going to have to have this reinforced to take weight of the HR3 as it is 400kg of engine mounted on steel bearers in the middle of the boat.

Am I right in thinking the tourqe that this engine produces could be an issue or would a 5mm base plate be able to handle the stress of the HR3.

 

The gearbox I intend to use is going to be either a PRM 101 or a PRM 160, the gearbox is to be remotely mounted away from the engine on the engine room bulkhead under the bedroom. The prop shaft would be supported by using 3 carry bearings mounted on bearers secured to the base plate.

 

This HR3 Is an ex Generator engine and has no variable speed but I can replace the govener at a later date.

 

Any advice is greatly appreciated

Regards

TCB

[RLWP]

Best advice is find a boatyard that is used to doing this sort of job and work with them

 

I'm working on a BMC 1500 today with a very similar history, I'm expecting it to be OK now

 

Richard

[David Mack]

The BMC could be fixed, or replaced with an exchange unit.

 

But the HR3 is a much nicer engine, although being air cooled (unless its a HRW3) you will need to add cooling ducts, and will lose the benefit of free hot water.

 

If your hull has substantial enough cross members in the area where the new engine is going, then it may be fairly straightforward to weld in some new longitudinals to bolt the engine down to. But if they are light, it would be better to take them out (or cut them back), get some new proper engine beds fitted,  then add suitable reinforcement back to the hull sides. The framing will take the torque, so bottom plate thickness shouldn't be an issue. That said 5mm sounds thin - is this how it was built, or a recent survey measurement showing some loss from an original 6mm (or more) baseplate?

 

As Richard says, unless you know how to do this it would be better to let an experienced boatyard take the strain.

[BWM]

The baseplate shouldn't be a problem as similar engines were installed in historic working boats (6mm), they were however mounted on hefty framework. On thing to consider is wether you have sufficient draft for a suitably large propeller. As others have said, it would be worth consulting an experienced yard before going ahead. 

 Another consideration might be hydraulic drive, as this will allow a more useful headroom in the bedroom-a propshaft running through will seriously reduce this.

Edited July 24, 2018 by BWM

[RLWP]

4 hours ago, RLWP said:

I'm working on a BMC 1500 today with a very similar history, I'm expecting it to be OK now

 

Richard

As predicted, 1500 now runs on on four cylinders with minimal smoke. Just needs advancing a little to be clean

[David Mack]

6 hours ago, TheCandleBoat said:

 

The gearbox I intend to use is going to be either a PRM 101 or a PRM 160, the gearbox is to be remotely mounted away from the engine on the engine room bulkhead under the bedroom. The prop shaft would be supported by using 3 carry bearings mounted on bearers secured to the base plate.

 

Why the remote gearbox? The gearbox output shaft is lower than the input shaft, so by putting the gearbox on the back of the engine you will have a lower shaft through the back cabin, meaning a lower floor and more headroom. A separate gearbox under the floor will mean an even higher section of floor over the box itself.

[TheCandleBoat]

4 hours ago, David Mack said:

The BMC could be fixed, or replaced with an exchange unit.

 

But the HR3 is a much nicer engine, although being air cooled (unless its a HRW3) you will need to add cooling ducts, and will lose the benefit of free hot water.

 

If your hull has substantial enough cross members in the area where the new engine is going, then it may be fairly straightforward to weld in some new longitudinals to bolt the engine down to. But if they are light, it would be better to take them out (or cut them back), get some new proper engine beds fitted,  then add suitable reinforcement back to the hull sides. The framing will take the torque, so bottom plate thickness shouldn't be an issue. That said 5mm sounds thin - is this how it was built, or a recent survey measurement showing some loss from an original 6mm (or more) baseplate?

 

As Richard says, unless you know how to do this it would be better to let an experienced boatyard take the strain.

Hi David thanks for your reply.

The base plate on my boat is 5mm original thickness and has almost no pitting on it at all I had a survey recently done and I was very surprised that I didn't need any over plating at all.

The concern I have is some people have said and I have seen some very substantial framework holding these engines and it made me wonder if this could have been too much for the boat, I have got a very experienced welder who is on board for the project and is going to be doing the work for me as I can not weld, the current plan after much discussing is to remove the floor frame work around the new engine room and install two longitudinal beams the length of the boat and then three or four cross beams that also extend up the sides of the hull to spread the weight and torque that this engine produces.

14 minutes ago, David Mack said:

 

Why the remote gearbox? The gearbox output shaft is lower than the input shaft, so by putting the gearbox on the back of the engine you will have a lower shaft through the back cabin, meaning a lower floor and more headroom. A separate gearbox under the floor will mean an even higher section of floor over the box itself.

As for remote mounting of the gearbox this is an industrial engine and I dont have any marine parts for it so the plan is to go direct drive from the engine through the gearbox and onto the propshaft that is to be inline to the stern gland.

With the gearbox mounted on the engine room bulkhead it makes mounting gearbox simpler and easier and I have no marine parts for this engine so this is the simple option to me personally, As for floor height it isnt going to be too bad as my floor runs down the right hand side of my boat not down the centre as the aft doors are on the right hand side, the prop shaft would run under my bed if you like with the gearbox being under my bed as well but with good access for maintenance and servicing.

3 hours ago, BWM said:

The baseplate shouldn't be a problem as similar engines were installed in historic working boats (6mm), they were however mounted on hefty framework. On thing to consider is wether you have sufficient draft for a suitably large propeller. As others have said, it would be worth consulting an experienced yard before going ahead. 

 Another consideration might be hydraulic drive, as this will allow a more useful headroom in the bedroom-a propshaft running through will seriously reduce this.

Currently Chiquita sits around the 2ft 6in area but as there are no vents and drain holes in the sides of the hull the draft could be increased to suit but the prop size I am fitting is a four blade prop at 15x18 as I can not fit anything bigger as I would hit the bottom of the current fuel tank and the rudder from memory this is less then an inch from the fuel tank, the current prop is a 15 10 but the BMC seems fine with it and doesnt seem to be overworked.

2 hours ago, RLWP said:

As predicted, 1500 now runs on on four cylinders with minimal smoke. Just needs advancing a little to be clean

Richard, That is great news would you like my bucket of bolts for spare parts, I dont want anything for it just get it out my way haha.

 

Thank you for all your advice everyone much appreciated 

 

 

 

 

[RLWP]

28 minutes ago, TheCandleBoat said:

Richard, That is great news would you like my bucket of bolts for spare parts, I dont want anything for it just get it out my way haha.

 

 

Yes.

 

A reconditioned pump and a bit of time and it will be a very saleable engine

 

Richard

[alan_fincher]

32 minutes ago, TheCandleBoat said:

Currently Chiquita sits around the 2ft 6in area but as there are no vents and drain holes in the sides of the hull the draft could be increased to suit but the prop size I am fitting is a four blade prop at 15x18 as I can not fit anything bigger as I would hit the bottom of the current fuel tank and the rudder from memory this is less then an inch from the fuel tank, the current

 

 

15" diameter x 18" pitch?

Even if 4 blade, and assuming the reduction on your box no more than 2:1, that sounds very undersized for an HR3.

What reduction will your box be?

15" props are for egg whisk type installations, IMO, not for something slow revving with the grunt of an HR3.

[TheCandleBoat]

18 minutes ago, alan_fincher said:

 

15" diameter x 18" pitch?

Even if 4 blade, and assuming the reduction on your box no more than 2:1, that sounds very undersized for an HR3.

What reduction will your box be?

15" props are for egg whisk type installations, IMO, not for something slow revving with the grunt of an HR3.

Hi Alan, Thanks for your comment.

 

The calculations for the propeller were that I shall be fitting a 2:1 gearbox and to my calculations below it appears that I could do with fitting a 17 or 18 inch prop but because I can not go larger on Dia I have to increase the pitch of the blades to make up for the same thrust of the prop, during my research the HR3 will tickover to 400 rpm, My BMC ticks over at 750, For sake of argument we will say that the BMC runs at 800, the bmc has a 3.1 gearbox this in tickover spins the current prop at 266 rpm in tickover. With the HR3 it is half the speed of the BMC being in at 400 rpm, this is going through a 2.1 gearbox and would produce 200 rpm at the prop, My HR3 will rev to 2200 rpm max, the BMC  would do 3000 rpm max so there isnt much in the way of difference of RPMs its more over gearbox ratios at the moment I think, Please correct me if I wrong.

 

Below are my calculations for the prop sizes and since i cant fit anything bigger then at absolute max 16 inches dia I must increase the pitch.

 

 

Waterline length in feet:	50 feet
Beam at the waterline in feet:	6.10 feet
Hull draft in feet (excluding keel):	2.6 feet
Vessel weight in pounds:	40000 lbs
Engine Horsepower:	44 HP
Number of engines:	1
Total Engine Horsepower:	44 HP
Engine R.P.M. (max):	2200 RPM
Gear Ratio:	2:1
Shaft R.P.M. (max):	1100 RPM
Number of shaft bearings (per shaft):	3
Desired speed in Knots:	6 knots

Horsepower Calculations

This will calculate the maximum horsepower and torque available at the prop(s).
Total available horsepower at the engine(s):	44 HP
Total available torque ft/lbs at the engine(s):	105 ft/lbs
Horsepower loss of 3% per gearbox:	- 1.3 HP
Horsepower loss of 1.5% per shaft bearing:	- 2.0 HP
Total horsepower available at the propeller(s):	40.7 HP
Total torque ft/lbs available at the propeller(s):	194 ft/lbs

Speed & Power Calculations

Basic displacement speed and horsepower required
Displacement hull speed (1.34 X sqrt of waterline length):	9.48 Knots
Minimum horsepower required at propeller(s) for Hull speed:	87.3 HP
Calculations based on desired speed and available HP
HP required at propeller(s) for desired 6 knots speed:	20 HP
Estimated maximum speed with existing 44 horsepower: This is the speed we will use for the propeller size.	7.55 Knots
At this point it is important to note that all of the calculations above are based on full RPM and HP. Most engines are rated to run at a percentage of thier full RPM. This is what will determine your maximum cruising speed. The propeller sizing calculations below are based on 90% of full RPM. This gives the engine some reserve power to allow for variable loading in the vessel.

 

Propeller Size

Number of blades	Diameter (inches)		Pitch (inches)
2 Blade	21.0	X	13.1
3 Blade	20.0	X	13.0
4 Blade	18.8	X	12.7

 

Many thanks 

TCB

[BWM]

1 hour ago, TheCandleBoat said:

Hi David thanks for your reply.

The base plate on my boat is 5mm original thickness and has almost no pitting on it at all I had a survey recently done and I was very surprised that I didn't need any over plating at all.

The concern I have is some people have said and I have seen some very substantial framework holding these engines and it made me wonder if this could have been too much for the boat, I have got a very experienced welder who is on board for the project and is going to be doing the work for me as I can not weld, the current plan after much discussing is to remove the floor frame work around the new engine room and install two longitudinal beams the length of the boat and then three or four cross beams that also extend up the sides of the hull to spread the weight and torque that this engine produces.

As for remote mounting of the gearbox this is an industrial engine and I dont have any marine parts for it so the plan is to go direct drive from the engine through the gearbox and onto the propshaft that is to be inline to the stern gland.

With the gearbox mounted on the engine room bulkhead it makes mounting gearbox simpler and easier and I have no marine parts for this engine so this is the simple option to me personally, As for floor height it isnt going to be too bad as my floor runs down the right hand side of my boat not down the centre as the aft doors are on the right hand side, the prop shaft would run under my bed if you like with the gearbox being under my bed as well but with good access for maintenance and servicing.

Currently Chiquita sits around the 2ft 6in area but as there are no vents and drain holes in the sides of the hull the draft could be increased to suit but the prop size I am fitting is a four blade prop at 15x18 as I can not fit anything bigger as I would hit the bottom of the current fuel tank and the rudder from memory this is less then an inch from the fuel tank, the current prop is a 15 10 but the BMC seems fine with it and doesnt seem to be overworked.

Richard, That is great news would you like my bucket of bolts for spare parts, I dont want anything for it just get it out my way haha.

 

Thank you for all your advice everyone much appreciated 

 

 

 

 

I should have said the distance between the bottom of the counter to the skeg, rather than draft but by the sound of it you do have limited space. The prop you are considering may struggle, the difference being the type of power the engine will produce  - the hr3 producing more torque against the horsepower of the bmc. I can't remember why, but when calculating ours the advice from the supplier was to avoid four blades for canal use.

  

Edited July 24, 2018 by BWM

[alan_fincher]

So, for a 4 blade the prop calculator suggests 18.8" x 12.7"

You are proposing instead 15" x 18", i.e the swept area is less than 2/3rds of the recommendation, which you hope to make up by having the pitch significantly more than the diameter.

I'm really not sure that will work at all well.

If you can only swing a 15" prop, I would suggest that an HR3 on a 2:1 reduction is not really a suitable engine.

[Boater Sam]

3 to 1 gearbox on  Bmc 1.5 is unusual, are you sure? All I have seen are 2 to 1.

My 50 ft boat with 1.8 BMC runs a 18" X 10.5 Crowther High Efficiency prop and is excellent, tick over 650, pulls 2800 if desperate or 2 water skiers. Draught 34".

15" is an egg whisk.  Could I suggest a word with Crowthers about a high efficiency prop with a bigger blade area?

 

[TheCandleBoat]

11 minutes ago, alan_fincher said:

So, for a 4 blade the prop calculator suggests 18.8" x 12.7"

You are proposing instead 15" x 18", i.e the swept area is less than 2/3rds of the recommendation, which you hope to make up by having the pitch significantly more than the diameter.

I'm really not sure that will work at all well.

If you can only swing a 15" prop, I would suggest that an HR3 on a 2:1 reduction is not really a suitable engine.

If this is the case I can most likely reduce the pitch and go 1.1 for the gearbox reduction and reduce the pitch and increase the shaft speed which I think looking over the calculations could reduce the issues of the Dia and too much pitch and increase the speed the prop turns, I am sure I have no lack of torque here with the HR3

 

TCB

[RLWP]

Sorry, you plan on using the HA at 2200rpm, and a cruising speed of 6 knots?

 

An HA in an engine room flat out will drive you crazy. Most narrowboat installations use well below the designed engine speed, substituting a massive prop to give an engine tht's nice to live with

[alan_fincher]

4 minutes ago, TheCandleBoat said:

If this is the case I can most likely reduce the pitch and go 1.1 for the gearbox reduction and reduce the pitch and increase the shaft speed which I think looking over the calculations could reduce the issues of the Dia and too much pitch and increase the speed the prop turns, I am sure I have no lack of torque here with the HR3

 

I don't think that you'll get a suitable PRM box on a 1:1 reduction.

I think 1.5:1 is the lowest standard ratio.

(which could give options for a "less unsuitable" prop, I guess.)

With the limitations you have on prop size, I'd try to sort out the BMC.

[TheCandleBoat]

6 minutes ago, RLWP said:

Sorry, you plan on using the HA at 2200rpm, and a cruising speed of 6 knots?

 

An HA in an engine room flat out will drive you crazy. Most narrowboat installations use well below the designed engine speed, substituting a massive prop to give an engine tht's nice to live with

 

Sorry I should have been a little more clear, That was the absolute maximum speed the HR3 would be capable of delivering, these were the calculations for the same engine but lower RPM speed, These were the Real world RPM usage figures.

 

Waterline length in feet:	50 feet
Beam at the waterline in feet:	6.10 feet
Hull draft in feet (excluding keel):	2.6 feet
Vessel weight in pounds:	40000 lbs
Engine Horsepower:	44 HP
Number of engines:	1
Total Engine Horsepower:	44 HP
Engine R.P.M. (max):	800 RPM
Gear Ratio:	1:1
Shaft R.P.M. (max):	800 RPM
Number of shaft bearings (per shaft):	3
Desired speed in Knots:	6 knots

Horsepower Calculations

This will calculate the maximum horsepower and torque available at the prop(s).
Total available horsepower at the engine(s):	44 HP
Total available torque ft/lbs at the engine(s):	289 ft/lbs
Horsepower loss of 3% per gearbox:	- 1.3 HP
Horsepower loss of 1.5% per shaft bearing:	- 2.0 HP
Total horsepower available at the propeller(s):	40.7 HP
Total torque ft/lbs available at the propeller(s):	267 ft/lbs

Speed & Power Calculations

Basic displacement speed and horsepower required
Displacement hull speed (1.34 X sqrt of waterline length):	9.48 Knots
Minimum horsepower required at propeller(s) for Hull speed:	87.3 HP
Calculations based on desired speed and available HP
HP required at propeller(s) for desired 6 knots speed:	20 HP
Estimated maximum speed with existing 44 horsepower: This is the speed we will use for the propeller size.	7.55 Knots
At this point it is important to note that all of the calculations above are based on full RPM and HP. Most engines are rated to run at a percentage of thier full RPM. This is what will determine your maximum cruising speed. The propeller sizing calculations below are based on 90% of full RPM. This gives the engine some reserve power to allow for variable loading in the vessel.

 

Propeller Size

Number of blades	Diameter (inches)		Pitch (inches)
2 Blade	25.4	X	18.0
3 Blade	24.2	X	17.9
4 Blade	22.8	X	17.5

 

 

As you can see the prop size once again is an issue but I am sure there are ways around this by using a some going 1.2 or even 1.3 at the extreme  to increase the shaft over the engine RPM engine speed this could be a little extreme but I am sure there are ways around these things and I am very sure I have no lack of torque from the HR3.

 

4 minutes ago, alan_fincher said:

 

I don't think that you'll get a suitable PRM box on a 1:1 reduction.

I think 1.5:1 is the lowest standard ratio.

(which could give options for a "less unsuitable" prop, I guess.)

With the limitations you have on prop size, I'd try to sort out the BMC.

In all honesty Alan I have had enough of the BMC yes its a nice engine but its just not worth my time spending another 3K on it with already spending 4k on having it rebuilt back in 2015 by Calcutt boats who did not do a good job on it for it to fail this soon, its not worth the time or the money, Id rather have the HR3 in it as its more reliable then a BMC anyway.

[RLWP]

1 minute ago, TheCandleBoat said:

In all honesty Alan I have had enough of the BMC yes its a nice engine but its just not worth my time spending another 3K on it

Today's job was a lot, lot less than that

 

Richard

[David Mack]

This hull of yours sounds very odd. Apart from Springers I can't think of any other leisure narrowboat built with a less than 6mm bottom, but you say it was originally 5mm. That suggests it may have been very much a budget shell, in which case I wonder how much effort is worth putting into it.

You say the draft is 2' 6" yet you can only swing a 15" prop without hitting the bottom of the fuel tank. 

It doesn't add up!

[alan_fincher]

39 minutes ago, TheCandleBoat said:

In all honesty Alan I have had enough of the BMC yes its a nice engine but its just not worth my time spending another 3K on it with already spending 4k on having it rebuilt back in 2015 by Calcutt boats who did not do a good job on it for it to fail this soon, its not worth the time or the money, Id rather have the HR3 in it as its more reliable then a BMC anyway.

 

I sincerely wish I could have kept the level of spend required to rebuild one of my Lister HA2s down to the total spend I made on a BMC 1800 over 10 years of ownership.

I'll duck out, but I still think the amount of space you have for the prop makes an HR3 an unsuitable choice.

(Plus it is just too powerful for a 50' leisure narrow boat, IMO).

[X Alan W]

With all the hassle you are going to encounter time & money wise I would seriously consider replacing the motor with like (BMC 1500 )either wih replacement/rebuilt Etc the GMC unit in good nick ts although dated is a reliable unit(#of units in use ) the recon unit will fit with little /no modification & a good amount less cost But then again It's your call

[Neil Smith]

get Richard to give you a quote to fix the bmc, it will be cheaper than you think, not all are as expensive as calcutt.

 

Neil

[Alan de Enfield]

20 hours ago, TheCandleBoat said:

 

Sorry I should have been a little more clear, That was the absolute maximum speed the HR3 would be capable of delivering, these were the calculations for the same engine but lower RPM speed, These were the Real world RPM usage figures.

 

 

Are you aware of the RCD regulations that came into force in 2017 (regarding the re placing the engine of a boat) ??

[Neil Smith]

Is that something to do with emissions and affects boats built after a certain year unless replica historic boats.

 

Neil

[philjw]

On 24/07/2018 at 13:09, TheCandleBoat said:

 

I have a 1982 50ft skillcraft NarrowBoat with a BMC 1500 engine in it.

Isn't this boat too old to be affect by the RCD?

Edited July 26, 2018 by philjw
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