BMC Captain Diesel

[Gary Fox]

Yes they're good engines, capable of constant full-power running for months on end, with regular oil changes. I spent a whole season thrashing one on a passengercarrying narrowboat, 7 days a week of full revs, no issues at all. It was eventually replaced for cosmetic reasons by a Russel Newberry, which was a disaster.
There are plenty of mechanics with intimate knowledge of them, and cheap spares. Much better to find one of these in an old boat, than a 70's Volvo! The common PRM boxes are also very long lasting.

 

[TNLI]

The BMC 1.5 Diesel engine was probably the most widely used engine within the marine industry throughout the 1960'sand 70's. Its ability to withstand abuse, abundant and cheap spares parts made it the most favoured engine in the hire boat industry. Many companies marinised the engine and sold it as a ‘turn key’ ready to run kit for boat installation. Thorneycroft, CT marine, Tempest and Newage all offered theengine marinised and ready to run.
Perkins offered the 4.107 but this was bigger, more expensiveand technically more advanced, which meant it was more difficult to repair and spare parts were very expensive. With this in mind most of the hire fleet operators fitted 1.5 BMC engines as standard.
I have one and have read many things over the past 30 yrs..

The Good Points
1. Excellent reliability. Easy to find spare parts, relatively cheap and easy to maintain.
2. Economical diesel fuel consumption burning less than a gallon per hour working under normal loads.
3. Good access to most parts of the engine including the diesel injector pump
4. In good condition, these engines are almost as smooth as any ‘modern’ diesel engine of today
.5. Standard Lucas automotive starter motor and alternator can be used.

The bad points.
They can twist the crank if overheated.
They like clean fuel
oil leaks..
It really is that simple !

Asap supplies and many other retailers sell most of the parts off the shelf but the best part is the price.
I treated mine to a new duplex cam chain, tensioner and gasket - £18 (retail) New fuel lift pump £24 .. The parts are very cheap when rarely needed.
A bmc can be professionally rebuilt by specialist companies such as calcutt for less than half the price for a new diesel engine.
One similar business (i can remember who it was) had a statement something like - If we had to re engine one of our hire boats with a new beta, nani or recon bmc we would chose the bmc every time as 25 years down the road when the new ones have had it the bmc will still be going.

Mine was born in 1965, did many hundreds of thousands of miles in a j2 morris van. Around 1980 it was reconditioned and fitted to my current boat.
4 Years later the boat was nearly wrecked when dismasted crossing biscay. She lay in a boatyard for 6 years and had a foot of rainwater inside..
I aquired the boat and had to dismantle the engine as it was seized, probably from all the damp?
I beat the pistons out with a block of wood, picked the seized rings out of the pistons , lightly sanded the bores, bought new big and small end bearings and new rings, got the injectors and pump reconditioned - and it started and for for much less than £500.
27 years later it is still running..

If you can give it glow plugs for 20 secs and it starts then there is no reason why it should be problematic?

Very interesting post, as I'm trying to find a BMC 1500 to replace the badly siezed and broken, (Glow plug pin fell into a cylinder, but the skipper failed to shut the engine down until it siezed up), one that I sold off to a local expert who eventually gave up and dumped it in the channel with a stainless chain attached to a small marker bouy, (It's underwater, but can be found with a good GPS and tuna tower), fairly near a good spot to fish, (Some kind of wreck),

The twisted or cracked crankshaft that can result from serious overheating in the first case, or failure to change the main bearings when they are badly worn in the latter case, does concern me, as very few companies seem to replace the crankshaft or chain. New cranks are available, BUT I've no idea if they are any good or not. No point changing a wobbly crank for a new shiny far Eastern copy that then sufferes from serious corrosion, before snapping suddenly due to an invisible crack from a casting fault.

So if you know anything more about bad crank issues, like do you need to get the crank X rayed, or is dye marker good enough in crack detection terms ??

Also, if your boat has to spend time in the canals, or trolling at very low power settings, which major brand oil do you recommend ??

Which oil was OEM recommended for a BMC in the 70's in the UK ??

Old non turbo diesels don't really need a German Liqui Moly Synthoil, (The real McCoy chemical factory base stock), or a GTL (Gas To Liquid), base stock, (Shell Ultra 0 or 5w40 Acea A3/B4), they are happy with UK or US standard full synthetic, (It's a hydro cracked dinasaur base stock), like Mobil Delvac 10 or 15w40 Acea E4 and E6), or even an old dinasaur oil.

BUT, (it's a big but), using an oil that contains high levels of Moly as an additive, as many do, can increase low power related cylinder deposits to some extent, although nothing like as much a using cheap farm diesel that is contaminated with traces of Suphur, tar and varnish. Poor quality diesel is normally not an issue if filtered correctly, BUT at low power it can be bad news in cylinder deposit terms, as can worn injector tips.

There are some fairly expensive fuel additives that will help reduce deposits caused by bad fuel, BUT the only company I trust as regards serious fuel, or even oil additives is Liqui Moly, and it's far cheaper to just use real good diesel from a major brand garage.

PS: I never use any engine oil that is not a major brand one, by that I mean Liqui Moly, Shell, Mobil or Castrol, and make100% sure you are using an oil that complies with the engine manufacturers advise in Acea or API category and temperture range tables. For example, I use a straight SAE 30 in the tropics, (Constant temperature), but change to an 0 or 5w30 or 40 multigrade in Artic. The 30 grade does not contain VI additives that change the viscosity with temperature, so it often finishes up at the same actual viscosity when used.
Also be very careful with which exact version of Delvac or otherdiesel only oils you use, as the ones thay say they are good for diesels with DPF filters are no good, as they do not contain enough Zinc based anti wear and corrosion additives that old engines really do like.

Mobil Delvac XHP Extra 10W40 has a TBN, (Total base number), of 15 !! So it will really clean up sludge or even varnish to some extent, far better than any other cheap oil, AND it only has 50 ppm of high quality Moly, so is not going to add to the cylinder deposits in an old diesel used at low power too often.

 

[Boater Sam]

I have such an engine on a Colvic 31 motorsailer. It is working very well since 1976. I bought the boat in 1987 and had to replace the heat exchanger with a Bowman one. The engine is linked to a Newage (Coventry) gearbox. At the moment, I am unable to find replacement oil filters for this gearbox. Can anyone tell me where I could be able to find such filters.

Newage, now PRM advise that with modern oils the filter is not required and in fact they sell a blanking kit to replace it.

Or you can burn out the filter and refit the cleaned out can.

 

[Boater Sam]

Very interesting post, as I'm trying to find a BMC 1500 to replace the badly siezed and broken, (Glow plug pin fell into a cylinder, but the skipper failed to shut the engine down until it siezed up), one that I sold off to a local expert who eventually gave up and dumped it in the channel with a stainless chain attached to a small marker bouy, (It's underwater, but can be found with a good GPS and tuna tower), fairly near a good spot to fish, (Some kind of wreck),

The twisted or cracked crankshaft that can result from serious overheating in the first case, or failure to change the main bearings when they are badly worn in the latter case, does concern me, as very few companies seem to replace the crankshaft or chain. New cranks are available, BUT I've no idea if they are any good or not. No point changing a wobbly crank for a new shiny far Eastern copy that then sufferes from serious corrosion, before snapping suddenly due to an invisible crack from a casting fault.

So if you know anything more about bad crank issues, like do you need to get the crank X rayed, or is dye marker good enough in crack detection terms ??

Also, if your boat has to spend time in the canals, or trolling at very low power settings, which major brand oil do you recommend ??

Which oil was OEM recommended for a BMC in the 70's in the UK ??

Old non turbo diesels don't really need a German Liqui Moly Synthoil, (The real McCoy chemical factory base stock), or a GTL (Gas To Liquid), base stock, (Shell Ultra 0 or 5w40 Acea A3/B4), they are happy with UK or US standard full synthetic, (It's a hydro cracked dinasaur base stock), like Mobil Delvac 10 or 15w40 Acea E4 and E6), or even an old dinasaur oil.

BUT, (it's a big but), using an oil that contains high levels of Moly as an additive, as many do, can increase low power related cylinder deposits to some extent, although nothing like as much a using cheap farm diesel that is contaminated with traces of Suphur, tar and varnish. Poor quality diesel is normally not an issue if filtered correctly, BUT at low power it can be bad news in cylinder deposit terms, as can worn injector tips.

There are some fairly expensive fuel additives that will help reduce deposits caused by bad fuel, BUT the only company I trust as regards serious fuel, or even oil additives is Liqui Moly, and it's far cheaper to just use real good diesel from a major brand garage.

PS: I never use any engine oil that is not a major brand one, by that I mean Liqui Moly, Shell, Mobil or Castrol, and make100% sure you are using an oil that complies with the engine manufacturers advise in Acea or API category and temperture range tables. For example, I use a straight SAE 30 in the tropics, (Constant temperature), but change to an 0 or 5w30 or 40 multigrade in Artic. The 30 grade does not contain VI additives that change the viscosity with temperature, so it often finishes up at the same actual viscosity when used.
Also be very careful with which exact version of Delvac or otherdiesel only oils you use, as the ones thay say they are good for diesels with DPF filters are no good, as they do not contain enough Zinc based anti wear and corrosion additives that old engines really do like.

Mobil Delvac XHP Extra 10W40 has a TBN, (Total base number), of 15 !! So it will really clean up sludge or even varnish to some extent, far better than any other cheap oil, AND it only has 50 ppm of high quality Moly, so is not going to add to the cylinder deposits in an old diesel used at low power too often.

Originally straight 30s oil was spec.

Now 15W40 is fine but no synthetics at all. High zinc is not a requirement even though this is a flat tappet engine.

Cranks are not a big problem even though its only 3 bearing. In a canal situation you are most unlikely to ever break one. Dye testing is a good idea. Timing chains do wear eventually but replacing them and the slipper and tensioner is straight forward.

 

[AntarcticPilot]

Concerning the original question about horsepower, the bottom line is that a boat with a displacement hull (i.e. non-planing) can only effectively use so much power, because the power required to go faster increases sharply at a point related to the waterline length. The usual relationship quoted is that "hull speed" is reached at about 1.2 times the square root of the waterline length, but it varies according to the shape of the hull.

Power beyond that required to go through the water at that speed is rarely useful - ploughing into a head sea is about the only one a leisure boat will encounter. Of course, boats such as tugs use power in excess of that, but we aren't tugs!

A boat of around 30' length will do around 6-7 knots maximum. An engine of around 30 hp is plenty to drive a boat of that size at that speed, with a bit over. My own boat is fitted with a 28hp Volvo engine, and achieves hull speed at around ¾ throttle, and uses 2 litres of diesel an hour.

 

[Graham_Wright]

A useful post as my Countess 33 only achieves 3.5 knots using the BMC 1500. I assumed it was due to the low compression I found on one cylinder as the engine only achieves around 1000 rpm under load. It will go to ear threatening full revs off load. However, I never considered that the gearbox ratio might be wrong. It is 1:1 in ahead and 0.85:1 in astern. The engine was supplied marinised (Hamerrised?!) by T Norris and I have always assumed it was correct. The prop is as specified by the designer.
The gearbox is Hurth (now under different ownership I believe).

 

[Rappey]

Countess 33 only achieves 3.5

Is it possible your setup makes it hugely over propped so the poor little engine is overloaded as I'm also 33ft, 12tons and can rev right up to 4400 in gear but achieve close to max hull speed around 2100 rpm.

 

[Graham_Wright]

The prop (if I remember rightly) is 17 X 11.

 

[Boater Sam]

Hugely over propped, that size of prop needs a 2:1 gearbox.

 

[TNLI]

Originally straight 30s oil was spec.

Now 15W40 is fine but no synthetics at all. High zinc is not a requirement even though this is a flat tappet engine.

Cranks are not a big problem even though its only 3 bearing. In a canal situation you are most unlikely to ever break one. Dye testing is a good idea. Timing chains do wear eventually but replacing them and the slipper and tensioner is straight forward.

Straight 30 grades can last longer than multigrades if the oil is subject to high temp shearing, but that's not going to be a factor in a normally aspirated engine used mostly at low power. I've used them a lot in the tropics, where cold start performance does not matter.

15w40 is a good for the UK summer, but not in the winter. when 5 or 10w40 is a good range for an older diesel. Although some diesel manufacturers, like Bukh recommend an 0w40 in very cold conditions.

Although I tend to prefer using an 0 or 5w30 oil in winter, I'm only going to use Xw40 grades due to potential fuel contamination of the engine oil lowering the actual viscosity.

The only issue using a real group 4 synthetic in a diesel concerns the drip rate from old oil seals held in position by sludge or varnish deposits. They don't damage the seals, but can cause a temporary increase in oil leaks until the seal conditions sort things out.

Zinc based additives are important for almost every part within the main oil circuit for corrosion protection,, BUT it's the bottom end main bearings that like Zinc the most. Boron Nitride and Moly additives tend to me more important for top end .

Every engine is different as the best oil change interval, and in reality the quality of the oil filter is as important.

Mobil make a very good old diese oil that works well,

 

[Rappey]

Should be 50 hr oil change interval for road use.
I do mine, if I remember .
Mines a 56 years old morris diesel. Came from a J2 van. Been a brilliant engine. It's never let me down.
By todays standards its noisy and heavy but it's just so reliable and cost virtually nothing to own .
I've used whatever grade mineral oil is available from wherever I buy it.
Is the oil really that important on such basic old technology ?

 

[TNLI]

Should be 50 hr oil change interval for road use.
I do mine, if I remember .
Mines a 56 years old morris diesel. Came from a J2 van. Been a brilliant engine. It's never let me down.
By todays standards its noisy and heavy but it's just so reliable and cost virtually nothing to own .
I've used whatever grade mineral oil is available from wherever I buy it.
Is the oil really that important on such basic old technology ?

Thanks for the reply, and I also think the BMC 1.5 is an awesome engine in terms of main block life expectancy. Non close tollerance diesels are far tougher than modern very close tollerance common rail injection diesels, in terms of how well they survive serious abuse, including poor quality lubricants and filters.

Changing the oil every 50hrs makes sense, as it does reduce the risks from fuel contaminating the oil, of the dreaded head gasket fried mayo.
Non glass matrix synthetic oil and air filters, are far better in terms of how much debris, sludge or wear related metals they stop when dirty, rather than clean. In fact most common cheap oil filters will stop 99% of 20 micron particles when the filter is almost full, BUT when they are new, they are only 96% efficient at 20 micron particle filtration.
So 100 minus 99 = 1% bypass when full, to 100 minus 96 = 4% bypass when new, so changing oil or air filters too often is bad news, the exact opposite of what most diesel owners think.
Changing oil filters alternate oil changes is a real good idea, although most oil filters will last far longer than 50 hours.

Yep, old engines make a real nice rumble, rather than the sewing machine rattle, although the rattle can be rather loud when you use too thin an oil.

Heavy! A BMC is nothing like as heavy as Bukh! Those red donkeys are the world class leader in HP per pound weight.

The quality of the oil and filters does make a real difference in main block life, BUT it's a lot less than the difference it makes with a modern Yanmar, or other fuel efficient, (The BMC is fairly good, but only at around 15 to 2000 max RPM ).

If you only use your diesel during the extended summer, it's important to change the oil just before your planned boating season ends. Used oil is more acidic than new engine oil, and corrosion is very important in terms of how long a block will last.
I also add soluble oil, (A type of light machine oil), along with anti freeze just before the winter starts,

As regards the actual oil, USE A MAJOR BRAND OIL ONLY, and by that I mean, Liqui Moly, Shell, Mobil or Castrol. If you are overseas and non of those companies oil products are available, then the biggest oil company in the area. So CEPSA when in Spain etc.
I've looke at a lot of VOA, (Virgin Oil Analysis), results over the years, and most of the supermarket engine oils are a disaster, and the non major brand special offers, a total scam in terms of incorrect Acea or API catergory, often a B1 not a B4! In terms of the very important anti wear and cleaner additives, hopeless!
Many cheap dinosaur engine oils contain more 10 to 20 micron sized particles when new, than a real class act full synthetic (GAs To Liquid), used oil!

Viscosity matters, particularly in winter, so using a 15w40 or straight 30 grade, will give the starter and battery a real hard time, and result in some significant block wear incidents, as the oil film fails keep the metal components apart%. So read the operating manual for good examples.

Finally if you have a real bad engine, try Mobil 1 10w60 (Acea A3/B4), it has a lot of real good oil and will slowly clean up, and in the Artic, Shell Ultra, 0w30 Acea A3/B4, not my beloved Mobil Delvac EXP 10w40 B4 truck oil..

Good quality fuel is also a main block helper, as the bad stuff causes varnish in the cyliders, valve guides and top end parts.

Here endeth the lubrication general rant, and long may your BMC lasteth.

 

[Graham_Wright]

Hugely over propped, that size of prop needs a 2:1 gearbox.

That's what I suspect. I followed the designer's recommendations. The gearbox is a Hurth HBW100 which, I think, only comes with almost straight through gearing.
Edit wrong!
What would you recommend or where is the best source of such information?

 

[Boater Sam]

Changing oil at 50 hours in a canal boat is tedious and unnecessary.

I have always changed oil at 200 to 250 hours and only changed the filter on alternate changes with BMCs. Never worried about oil quality, usually cheap 15W40 tractor oil from factors is used in all seasons. Supermarket oil is far too dear.

Over 40 years I have never had a BMC 1.5D or a 1.8D engine fail or wear out. The closest I came was one that finally dropped its worn out timing chain after its loud rattle had been ignored for too long. That only needed new sprockets, chain and tensioner/slipper kit to restore normal operation.

 

[TNLI]

Thanks for the reply or comment, 200 hours is far too long for the additives included in a major brand engine oil to function as intended. The main risk factors include low viscosity due to fuel contamination, (Old injection pump seals or worn rings), sludge & varnish formation due to the detergents in every good oil being depleted. The other real nasty one only shows up in a UOA (Used Oil Analysis), and that is an out of limits Silicon figure. It should be below 50 ppm for an old non close tollerance diesel, (30 ppm for a turbo diesel), although that nasty issue, (Ultra fine sand in effect), can be overcome by fitting a better air filter unit, OR changing the oil more often.

I00 hours for an OCI, and 200 hours for an oil filter should be OK in most cases, BUT the proof of the pudding is in the eating, and the only way to know if the oil really does need to be changed is to do what the big rig drivers, train companies and monster gen set owners do. So take a 200 ml oil sample and post it off to Blackstones or other cheap oil analysis company for a basic mass spectograph check and other tests. That costs about 25 quid. They will e mail you the results and a comment about the engine or oil.

15w30 or 40 (30 for a new engine or 40 for an old BMC) is perfectly OK, BUT using tractor oil is only OK if you really know what is in the oil in additive terms. FUCHS who own Liqui Moly, do make a real good 10w40 (Acea B4) that is used by many farmers in the EU, Germany in particular. It's a good cleaner with high Calcium based detergent levels, fairly similar to a diesel only version of Castrol GTX 10w40.

The 15w part is no good below an intial start temp of minius 5C and it will give the starter motor and battery a real hard time. 10w40 should be OK unless you are up North freezing to death, then try an 0w30 (5w40 for BMC is OK for minus 25C), for the ice bound season.

Anyone know which oil and filter brands the US or UK parts or rebuild folks recommend for the BMC 1500 ??

PS: The Artic BMC owners fit sump or all block pre heaters. The sump ones are easy to fit and use about 200w of 240v power for at least one hour prior to starting. Coolant cookers are better, but a real pain to install. They warm the entire block, use very little power and diesel fuel.
If you fit a coolant cooker, or just keep the engine bay warm, (Sump in particular), I would use a major brand straight 30 grade all year. If you have diesel fuel contamination issues, try a Liqui Moly oil thickner after 50 hours or so. That will really help keep the oil in grade and top up a few key additives. Never forget that changing oil or air filters too often can be real bad news, not good. Dirty filters are far more efficient than new ones, unless you buy synthetic core ones.

 

[Boater Sam]

Well fancy after, all these years and running BMC engines for many hundreds of thousands of hours I have been doing it all wrong!

Some how I think Not! Never broke one.

 

[Rappey]

Anyone know which oil and filter brands the US or UK parts or rebuild folks recommend for the BMC 1500 ??

Whatever fits . Haha. Most have had the spin on filter conversion, mine takes a mini (car) filter . The filter can be short 2-3" , medium or larger..

usually cheap 15W40 tractor oil

Your in luck as the engine also appeared in tractors, I think a Nuffield?

 

[TNLI]

Well fancy after, all these years and running BMC engines for many hundreds of thousands of hours I have been doing it all wrong!

Some how I think Not! Never broke one.

Famous last words!

The last owner of my wreck sure broke one, too much easy start acetone into the intake, (I found 2 cans after it was salvaged),

BMC diesels seem to fail due to overheating twisting the crankshaft, running out of oil and glow plugs that fail with the electrode falling into the cylinder, (The engine in my sunken wreck had failed due to too much easy start, knocking out the electrode before the boat was abandoned and sank)

If an engine runs out of oil, it will take quite some time before seizing, IF the oil contains enough in the way of anti wear additives, AND 50 ppm or more of Moly friction modifyer. Moly also reduces fuel consumption. When the oil film fails it's the additives that often save the day, although Liqui Moly Synthoil High Tech 5w40 (A3/B4) does not, as the base stock is so durable it does not need it.

 

[TNLI]

Whatever fits . Haha. Most have had the spin on filter conversion, mine takes a mini (car) filter . The filter can be short 2-3" , medium or larger..

Your in luck as the engine also appeared in tractors, I think a Nuffield?

I've no idea why anyone would use a spin on filter kit if a removable canister was fitted.

The real good thing about canisters is that you can inspect and even clean the filter element and avoid not changing it until it really does need changing. Good idea to change the O ring every tine it is cleaned.

 

[jaydee1976]

same with the ford watermota 1.6 diesel engine its only 29hp in a boat(never used in a car or van as its a converted cortina block) but in my kingfisher 30 its ok