Swaping Lister SR2 to a BMC 1800

[chris63]

Just wondering what problems I might have in doing the above, I know I will have to fit skin tanks and alter the mounting frame but will there be any other issues? cheers Chris.

[RLWP]

Skin tanks, modified engine bearers, new gearbox, drive flange and flexible coupling, new engine mounts, new exhaust on opposite side, new electrical system, cooling system, controls.

 

You can probably reuse the stop cable

 

Richard

Edited August 10, 2014 by RLWP

[luctor et emergo]

Why?

[chris63]

I have had two narrow boats with SR engines and now ready for a quieter engine, the SR2 that's in at the moment has no oil pressure whatsoever and we are on the Chesterfield canal, when we come back onto the canal from the tidal part of the trent [ West Stockwith ] we really struggle as it's under powered, so as try and sort the Lister out am thinking about putting a BMC in to hopefully give me a bit more power, also the weed is terrible at times on our canal and the engine is constantly running too hot, so a more powerful engine will hopefully chop the weed up better.

[RLWP]

Ah yes, good point. You'll need a new prop too

 

It will cost you more to install the BMC than to rebuild your Lister

 

Richard

[lexicon]

Do you have the 1.8 ready to install?

[chris63]

No not yet, just trying to work out the best route to go down, why should the prop be a problem? the prop on the boat at the moment is a 14 or 15ins not sure which with a 15 pitch.

[RLWP]

Because the prop depends on the boat, the gearbox and the torque curve of the engine. The torque curve of a high revving engine is very different to a low revving SR2

 

Richard

[chris63]

How would I find out what prop I would need.

[PhilR]

I doubt that a more powerful engine will help much at chopping up weed, but I can understand why you want a quieter and more powerful engine for the R.Trent.

But maybe the BMC will not be sufficiently quieter? They aren't the quietest of water cooled engines!

 

If your SR2 is still running with *no oil pressure whatsoever* that is a testament to British engineering. If you have room to fit an SR3 that might be another option? But you will need a new prop to get the benefit + some decent sound insulation.

 

If you are still intending to change the engine you might want to allow for a new prop too? Most of the BMC and Thorneycroft conversions have heat exchangers fitted which might be much cheaper than going to the expense of skin tanks.

 

If you go ahead please keep us posted.

Good luck.

 

EDited to add: A few more post have arrived whilst I was typing this.

 

Ideally an SR2 would have an 18 x 12. This might be OK for a BMC 1800 with max RPM around 3,000 and 2:1 reduction.

Edited August 10, 2014 by PhilR

[RLWP]

How would I find out what prop I would need.

Best bet is to talk it through with Crowthers. They will need to know what gearbox you are going to use though

 

Richard

 

BMC 1.5, cheap (if you can find one) £1000. A PRM if you can find one, £500. Skin tank, £500, prop, £150, other parts, £600

 

I'm guessing low here.

 

Last SR2 rebuild I did came out at under £2000, including removal and reinstallation and some gearbox work

Edited August 10, 2014 by RLWP

[chris63]

That's what I did with my last boat put a SR3 in and had the prop repitched to 15 and it worked fine, and we did sound proof it but that started to overheat, so had to remove I all. Yes the Listers are good, we still use the boat but only for short runs.

[RLWP]

So, why does your Lister overheat? Have you got you hot air ducts installed correctly?

 

Richard

[Stilllearning]

On the prop , is it possible that SRs rotate the opposite way to most other engines, so a new prop is unavoidable?

[PhilR]

I think the standard rotation is left hand

[alan_fincher]

I also think that, (engine-wise at least), a Lister SR will likely rotate the opposite way to the BMC.

 

So even if diameter and pitch are correct, (seems unlikely), I think the rotation will probably be wrong.

 

Adding a skin tank to a narrow boat not designed for one can be tricky, unless it goes on the outside rather than the inside of the swim.

[chris63]

As far as i know the air ducting's fitted correctly, i thought it would be running hot due to no oil pressure, was told the pitch on a prop for a sr2 should be 10.5 but the guy who had the boat before me had it re pitched to 15 due to the Trent.

[martyn 1]

I also think that, (engine-wise at least), a Lister SR will likely rotate the opposite way to the BMC.

 

SR's are available in either hand rotation although standard is anti clockwise looking at the flywheel. Anti clockwise is standard pretty much nowadays.

[RLWP]

 

SR's are available in either hand rotation although standard is anti clockwise looking at the flywheel. Anti clockwise is standard pretty much nowadays.

 

Pretty easy to tell from the fan housing.

 

Richard

[PhilR]

As far as i know the air ducting's fitted correctly, i thought it would be running hot due to no oil pressure, was told the pitch on a prop for a sr2 should be 10.5 but the guy who had the boat before me had it re pitched to 15 due to the Trent.

 

My SR2 was originally fitted with a 17x10½ ins Lister weedless prop. This was a bit under-propped (and useless in reverse) for the boat and I replaced it with a 17x12. This has performed well, although 18x12 would have been better if there was enough room above the skeg to swing an 18 ins prop.

 

Regarding your oil pressure, an SR in reasonable condition should start up with 50 psi when cold and drop to around 15 psi when hot. Have you checked the accuracy of your gauge? And do you really mean *no oil pressure*?

 

Regarding the ducting, the Lister recommended cross sections for the SR2 are: Inlet 78 sq ins. and outlet 60 sq ins. Those cross sections are for trunking up to 6 ft in length.

[gazza]

So, why does your Lister overheat? Have you got you hot air ducts installed correctly?

 

 

Richard

My guess would be the cooling fins are caked in oil, shite, leaves, dust etc. Unloved Lister's are prone to overheating if the fins have never been cleaned.

 

Mr lister used to put a lovely picture of an engine with the caption 'let me breath' in the manual.

 

An sr2 is a bit of a weedy thing, I'd be tempted for a sr3 space permitting.

 

An engine change is a fairly big and costly undertaking, especially going from air cooled to water cooled.

 

I have just replaced a Stuart Turner for a Kubota d722, both water cooled, fair bit of expense and hassle for the owner.

You have the disadvantage of having to start complete anew if you go down the BMC route.

[robmilton]

Hi Chris, I did exactly the same conversion two years ago to my boat and don't regret it for a second, I loved the character of the lister but not the hot smell and smoke when it got too hot, I picked up a 1.8 Bmc from eBay fitted with a hurth gearbox (which will happily run in either direction) and had a skin tank fitted , lots more power no smell and hot water in abundance!, the engine mounts width wise are the same and the prop was just a little overproped but not too be worried about , I have however fitted a square bladed prop now which works great and is right for the engine.

I wouldn't personally go for the 1.5, if your going to do it try for the 1.8, much stronger in my opinion.

Best of luck.

Hi again, one on there now item number 331279542263 for £500 with a prm box.

[gazza]

Whilst a hurth box will run in either position A or B, you have to derate it for continuous operation in position B, I don't have the figures to hand, but if I reacall a hurth 50 goes from 20hp to 16hp in continuous operation in b position. The same holds true for a the bigger mechanical boxes.

We have a velvet drive on a BMC, its direction can be changed quite simply by altering the position of the pump at the front of the gearbox.

Excellent if expensive box. Not too common on eBay etc.

Forgot to add, the ratio is different in a and b on a hurth, again can't recall exactly but i think a hurth 50 is 2.25:1 in A and 1.8:1 in B

 

Same applies for the bigger boxes but figures need checking. Let Google do the work....

[pete.i]

 

My SR2 was originally fitted with a 17x10½ ins Lister weedless prop. This was a bit under-propped (and useless in reverse) for the boat and I replaced it with a 17x12. This has performed well, although 18x12 would have been better if there was enough room above the skeg to swing an 18 ins prop.

 

Regarding your oil pressure, an SR in reasonable condition should start up with 50 psi when cold and drop to around 15 psi when hot. Have you checked the accuracy of your gauge? And do you really mean *no oil pressure*?

 

Regarding the ducting, the Lister recommended cross sections for the SR2 are: Inlet 78 sq ins. and outlet 60 sq ins. Those cross sections are for trunking up to 6 ft in length.

Genuine question. What is a weedless prop?

[robmilton]

The hurth box I have is the 100 with 2:1 reduction and is the same in either direction. Had no problems with it so far.