Thornycroft diesel - any good?

Rivers & creeks

Rivers & creeks

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The probable new boat has a Thorneycroft 230 4 cyl 3.7 Litre diesel engine that is about 75hp. Two questions I'd like to try and answer - the first is your thoughts on what this engine is like. Any known issues to look for and spares availability and prices.

The second issue is likely fuel consumption at say 75% revs - what other variables would I need to work out consumption? I'm used to a 9.hp petrol outboard!

Thanks,

Simon
 
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slow revving heavy beasts derived from lorry engines.

I had one in a M/S for 5 years with 3600 hours on the clock, and all I ever did was change the oil and filters from time to time. Starts well, with a bit of blue smoke which disappears as soon as the engine warms up - which takes a good time about 20 mins to warm the block, gearbox and exhaust to a proper full operating temp of around 170F.


Spares from everywhere.
 
Muddy Paws said:
The probable new boat has a Thorneycroft 230 4 cyl 3.7 Litre diesel engine that is about 75hp. Two questions I'd like to try and answer - the first is your thoughts on what this engine is like. Any known issues to look for and spares availability and prices.

The second issue is likely fuel consumption at say 75% revs - what other variables would I need to work out consumption? I'm used to a 9.hp petrol outboard!

Thanks,

Simon
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fuel consumption as a rule of thumb
1 ltr per 10 hp
 
For spares you can go to ASAP or Thornycroft themselves. I just replaced the fresh water pump and upgraded the oil filter on my T90 with new parts from Thornycroft. It probably will benefit from a decent radflush treatment of the fresh water system
 
Thornycroft Diesel Engine

I have a Thornycroft 154 engine - smaller version of yours - which develops around 50HP. Boat is a 39ft cruising ketch.

Eight years with me and about 30 years old, it runs fine after that initial smoky start mentioned earlier.

Spares from ASAP, and many peripherals [filters, etc] sourced from Halfords and other motor factors.

Fuel consumption under load is in the range 3/4 to 1 gallon per hour.

Old technology - but perhaps a good thing?
 
My last boat had a Thornycroft (no 'e') 230. I'd echo the comments above about fuel consumption and spares, with a couple of additional points.

1. Some spares are cheap - when the old starter motor got slower and slower I installed a new one which only cost me £90. Filters etc are all very easy to get hold of.

2. It was quite hard to bleed and I would have to finish off the job with easystart in order to force through the diesel. I wondered if the injector pump needed rebuilding. Quoted £800. Decided it was fine! So some spares are less cheap.

It ran like a dream, though, and had been providing solid service for 30 years.
 
Thanks, those are all really helpful posts.

On the question of fuel consumption, assuming she is over engined (75hp seems a lot for a 31 footer) then does that mean consumption is less than stated above?
 
Muddy Paws said:
Thanks, those are all really helpful posts.

On the question of fuel consumption, assuming she is over engined (75hp seems a lot for a 31 footer) then does that mean consumption is less than stated above?
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in reality just the hp you use at the time.
my old perkie 4108 rated @ 48 hp @ 4500 rpm
with the prop as set up when we bought the boat the engine maxed out @ 2900 rpm say 38 hp
i re engined with a Nanni rated 37.5 hp @ 3000 rpm
the new engine need the MaxProp set to a courser pitch to get it just below 3000 rpm.
we get average of 3 lts per hr cruising & 2000 > 2400 rpm.
2400 gives 7 kts
 
From the MS-05-230 Thornycroft 230 leaflet, ratings are as follows:

http://www.asap-supplies.com/marine/thornycroft-230-engine-information

1250RPM 36BHP 7.64LPH
1500RPM 43BHP 8.91LPH
2000RPM 56BHP 12.23LPH
2400RPM 63BHP 14.78LPH


Do those figures mean litres per hour???? If so at just over half revs it's using almost 2 gallons an hour - or about 3 miles to the gallon. Is that right?
 
Muddy Paws said:
From the MS-05-230 Thornycroft 230 leaflet, ratings are as follows:

http://www.asap-supplies.com/marine/thornycroft-230-engine-information

1250RPM 36BHP 7.64LPH
1500RPM 43BHP 8.91LPH
2000RPM 56BHP 12.23LPH
2400RPM 63BHP 14.78LPH


Do those figures mean litres per hour???? If so at just over half revs it's using almost 2 gallons an hour - or about 3 miles to the gallon. Is that right?
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We had a big prop, and I used to go everywhere at about 1200 rpm, which I reckoned at about a gallon an hour - so the manual's probably about right. 33 ft wooden motorsailer, 13 tons.
 
Sorry to ask a dumb question, there is another boat with a 55hp engine, will that use less fuel at say 40hp than the bigger engine also running at 40hp?
 
Muddy Paws said:
Sorry to ask a dumb question, there is another boat with a 55hp engine, will that use less fuel at say 40hp than the bigger engine also running at 40hp?
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Not a dumb question at all. Simple answer not necessarily so.

People seem to forget time and time again that 'propellers move boats not the engines'

Take a look at the propeller demand curve of any engine, you will see that other than at rated rpm the propeller is asking for less power than engine has available. This is why a prop curve to the exponent of say 2.7 is a dramatically different shape from the power curve.

Looking at the Thornycroft #'s posted by ASAP supplies they appear to be full load power curve figures which are pretty meaningless.

Going back to basics the Leyland '98' Series engines were based on an older generation of engines designed by Morris Commercial/BMC Commercial in the late 40's early 50's. The design of thes engines relied on much technical input from the Swiss Saurer concern. Pay no attention to people talking about other BMC indirect injection gasoline derived engines, they have nothing in common.

The revised '98' engines were more torqey that equivalent Perkins P4/4.236 or Ford and fuel consumption was certiainly on a par with Perkins and better then Ford Dorset four jug motors.

Going back to your original question, part load curve of a direct injection motor Vs lower power indirect injection motor of the same era often falls in favor of the higher power DI motor.

Thornycroft 230 was standard on Colvic Watson motor sailers and works real well. Parts cheaply available via tractor/JCB suppliers, remember this was standard JCB engine for years. Forget ASAP supplies, bit like the poster saying CAV pump overhaul was quoted £800, he must have told pump shop it was off a marine engine therefore attacting manditory premium. Raw water pump is plain old Jabsco and manifold is Bowman.

One major drawback is the wet liners, they will pinhole and or leak at the bottom seal unless you use Fleetguard DCA 4 water treatment. If engine uses DCA, liner problems NEVER arise.
 
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Wow thanks. Now excuse the numpty - what are 'wet lines' and are you saying those ASAP fuel consumption figures aren't correct? This diesel thing is a steep learning curve when you start from the bottom!
 
Muddy Paws said:
Wow thanks. Now excuse the numpty - what are 'wet lines' and are you saying those ASAP fuel consumption figures aren't correct? This diesel thing is a steep learning curve when you start from the bottom!
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Laterstarter (who was clearly no late starter as far as engines are concerned) hasn't come back yet, so I will.

Liners are the tubes pistons run up and down in, unless they run in the parent metal of the engine block itself. Wet liners are so-called bacause they're in physical contact with the engine's cooling fluid. So a hole in a wet liner links the crankcase and cooling jacket, which is not good.

I don't think he was saying that the fuel consumption figures weren't correct, just that they were correct only in a particular circumstance...oranges were not necessarily being compared with oranges. He suggested (I think) that generally a 75hp direct injection diesel being asked to deliver 30hp might be expected to do so more fuel efficiently than a contemporary 50hp indirect injection engine asked for the same power.
 
Muddy Paws said:
Wow thanks. Now excuse the numpty - what are 'wet lines' and are you saying those ASAP fuel consumption figures aren't correct? This diesel thing is a steep learning curve when you start from the bottom!
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Question re 'wet liners' has already been covered, as to fuel consumption you are not alone as to how diesel engine/propeller works. You are certainly no numpty by asking the question.

Think of the concept of the the throttle lever controlling all speed governor on a diesel engine as akin to cruise control on your car. You set the engine speed via your throttle lever, the governor only supplies sufficient fuel to hold the rpm you have set.

Consider this take the example of ASAP #'s 1,500 rpm representing 43 Hp on full load curve, however depending on propeller exponent demand from the propeller will be not much more than half that, so you have set throttle to 1,500 rpm, is the engine developing 43 Hp no! The governor is giving just enough fuel to develop say 26 Hp at 1,500 rpm or whatever propeller is demanding from the engine. The nearer to rated rpm you get the smaller the margin becomes.

Take a look at any propeller law (demand) curve to say 2.7 exponent and all becomes clear.
 
Thanks, that really makes sense. To check my understanding, let's assume 4LPH at 1500rpm motoring through water. Then we miraculously start motoring through treacle, I keep the revs the same but the LPH goes up significantly. In other words the propellor is only loading the engine by about 50% when motoring through water?
 
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