Anyone come across this engine type?

Rivers & creeks

Rivers & creeks

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Re engine project under way and I want to use a Mermaid JCB J444, 2200 RPM 84HP. It's replacing a 40 year old Thornycroft 230 68HP in a 34 foot Colvic Watson. Obviously it's the right sort of engine, lots of low rev torque and a big heavy crank shaft. But any knowledge of this particular engine? I can't afford a new one so I'm buying a 3000 hrs unit that's been recond and has a full refund warranty from a reputable supplier. Before I went engine hunting I'd never heard of the Mermaid JCB range but they've sold quite a few and it's based on a a very popular JCB dieselmax lump.

Another yard wanted to use a new Beta 60 which is on;y a 56HP unit and way lighter in every way. I'm not happy with that.
 
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The engine also holds the world land speed record for a diesel vehicle. Would have thought a Perkins 4/236 or the later Sabre version would be very suitable for your boat and more commonly available.
 
I agree, some owners have 110hp or more! But she displaces 12T and is a long keel with plenty of windage so head to wind and seas she needs a fair bit.
 
Tranona said:
The engine also holds the world land speed record for a diesel vehicle. Would have thought a Perkins 4/236 or the later Sabre version would be very suitable for your boat and more commonly available.
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Where would you get a decent used Sabre from a reputable source? Interested but I found it hard avoiding the refurbish-with-gloss-paint merchants.
 
Colvic Watson said:
Re engine project under way and I want to use a Mermaid JCB J444, 2200 RPM 84HP. It's replacing a 40 year old Thornycroft 230 68HP in a 34 foot Colvic Watson. Obviously it's the right sort of engine, lots of low rev torque and a big heavy crank shaft. But any knowledge of this particular engine? I can't afford a new one so I'm buying a 3000 hrs unit that's been recond and has a full refund warranty from a reputable supplier. Before I went engine hunting I'd never heard of the Mermaid JCB range but they've sold quite a few and it's based on a a very popular JCB dieselmax lump.

Another yard wanted to use a new Beta 60 which is on;y a 56HP unit and way lighter in every way. I'm not happy with that.
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Is this the one

http://www.mermaid-marine.co.uk/manufacturers/4-jcb/engines/14-j-444na1-74hp-j-444na2-85hp
 
Chalker said:
That's a lot of power for a 34 footer.
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That was my first thought. Maybe the OP is taking up water-skiing lol.
Have no experience of the JCB donk. I have a Ford Mermaid and have been
dealing with Mermaid for over 10 years now and they are just superb.
Spares, tech support, whatever you need they go OTT to assist.
 
I had the same Thorneycroft in my CW of the same size, but she weighed out at 16 tonnes in commission. :eek:

If the OP has a long-term relationship with the engine in mind, then a big donk is not excessive. He doesn't have to use all of the 84 horses at the same time.


My concern would be the propeller might need changing or repitching, otherwise top end power will be wasted or unusable. Likewise a check on the shaft diameter and connections to see if they are within the proposed new input range.
 
Hi,

Lots of commercial fisherman use them day in day out with no problems... having been on boats with both Sabres and Mermaids the Sabre probably had the edge on quality and both were ford based blocks back then, was talking to a friend who has twin 180 Mermaids and he was full of praise for the company, they remembered his boat and the engineer over 25 years ago fitted the engines new the exact block spec., they had one in and are going to rebuild it over next six months as my friend does not want it yet and will then do the same with the one they are taking out so he has a good spare... he said they were really helpful and the engineer gave him some really good hints and tips about the engines.
Sabres these days and for some time now have been based on the Perkins block again very good reports but don't think you will go too far wrong with a Mermaid... hope that helps
 
Colvic Watson said:
I agree, some owners have 110hp or more! But she displaces 12T and is a long keel with plenty of windage so head to wind and seas she needs a fair bit.
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Most regular sailboats are way underpowered & under propped. That is why they are so difficult to maneuver around the docks,etc.
They are eqpd with what I call a "get me home to mouth of harbour" engines.
Pardon the pun,but More power to you CW!!

Cheers/Len :encouragement:
 
CW's are usually over powered, in practice it damages the engines because owners never or very rarely go above 60% throttle, I've seen CW 25's with 45hp and CW 34's with 110hp engines! My 74hp is only nominally that, you're not supposed to use the last 10hp for more than 20minutes continuously - sort of emergency extra. I've been up near full throttle on a few occasions but cruise comfortably at 1800 out of 2300 RPM. That doesn't leave a lot in the bottle for when things get bouncy.
 
a story about JCB engines. JCB decided to design their own, contrary to industry best practice for the number of units they expected to sell. the result is a very reliable engine that led to a very reliable fleet of vehicles. One of the main reasons for the success of JCB is their reliability. So, it would seem that industry best practice, isnt.
 
Len Ingalls said:
60 Hz AC generators run at 1800 for years.:)
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Not sure how that helps. They are designed to run at those revs under load.

The OPs engine is also designed to run at 1800 continuous. Good installations in displacement boats should run at revs that draw approx 50% rated power at around 70% rated revs, which is what his does.
On the other hand the Volvo in my boat is rated at 3200 and runs continuous at 2300.

All it shows is the engine is correctly loaded in each case.
 
Caer Urfa said:
Most CW 34'-6" have at least a 100 hp engine and many were built with a 124 hp Perkins 6-354 on a 740mm dia fixed pitch prop as standard as you always want some welly in reserve for poor weather conditions.:)

Mike
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Then they must be way heavier than mine! Beachy Head, vile F7 on the nose with a big, big sea, the nastiest combination of wind and sea I've been in, not too windy but huge waves, all on the nose, breaking and flying over the wheelhouse. I'd left the main up and it was dead to wind slowing us down; I did once nudge the engine into 95% territory which unleashed 70 horses maximum, cleared the particular wave and came back down to 80%. So I guess we must be a uniquely easily driven CW35 not need 125hp! Gordon's holy trousers - do they do a spot of drag net fishing in their spare time :D Diesels like ours need to be worked hard from time to time and with 125hp I'd never be past 50% hp! But thanks for the reassurance I was beginning to think I'd over egged the pudding at 85hp.
 
Tranona said:
Not sure how that helps. They are designed to run at those revs under load.

The OPs engine is also designed to run at 1800 continuous. Good installations in displacement boats should run at revs that draw approx 50% rated power at around 70% rated revs, which is what his does.
On the other hand the Volvo in my boat is rated at 3200 and runs continuous at 2300.

All it shows is the engine is correctly loaded in each case.
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Many generators would run at varying loads from 0- 100%. My point being that a diesel,or any engine,does not have to operate at a specific load all of the time.
The load to be avoided is ~ 100% for long periods.
In fact,unless a vessel is powering long distances,the engine is running at various speeds in most cases.
An occasional burst of full power for a short time is healthy of course & long term idling or very low RPM is not healthy.
For the most part,the engines we use in our recreational boats are also used in gensets,trucks/cars,farm & industrial machinery,etc. & loads/RPM would vary greatly.

Cheers/ Len :)
 
Colvic Watson said:
Then they must be way heavier than mine! Beachy Head, vile F7 on the nose with a big, big sea, the nastiest combination of wind and sea I've been in, not too windy but huge waves, all on the nose, breaking and flying over the wheelhouse. I'd left the main up and it was dead to wind slowing us down; I did once nudge the engine into 95% territory which unleashed 70 horses maximum, cleared the particular wave and came back down to 80%. So I guess we must be a uniquely easily driven CW35 not need 125hp! Gordon's holy trousers - do they do a spot of drag net fishing in their spare time :D Diesels like ours need to be worked hard from time to time and with 125hp I'd never be past 50% hp! But thanks for the reassurance I was beginning to think I'd over egged the pudding at 85hp.
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Funny that people still believe that more power from an engine is "good" when in reality it is difficult to get a propeller (which is what moves the boat) to use the power and difficult to transmit power into speed through the water once you get to the point where the waterline length limits speed.

The knack of powering displacement boats is to choose an engine/gearbox/prop combination that achieves maximum hull speed at close to WOT. Weight is what drives the amount of power for a given LWL and therefore speed potential and as you have a very heavy boat you need a lot of power - but not 120! You could never use that amount of power.

Just to put it in context, my boat has the same speed potential as yours, but achieves that comfortably with only 28hp. However it only weighs 5.5 tons compared with your 12+. I am ignoring hull shape, windage etc but the principle holds.
 
Hadenough said:
Matter of interest, how many hours had your Thorneycroft done?
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The Thornycroft 230 was invented in 1723, about 250 years before engine hour counters. But it's been in commission for 36 of its 39 year life. Each year the two previous owners used it extensively, more than we do and we cruise for 3 months a year. So I'd guess at a minimum 20,000, barely run in when it comes to block, pistons, valves and crankshaft. But the ancillaries keep going and one day the wet liners will perforate, then it's a dead dog unless you have lots of skill, time and determination ;)
 
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