I've been looking for a decent Britannia for a while, and as luck would have it came across this one, 35 miles away Pretty much complete and still turns, but a bit tight. A couple of water pipes and fuel tap missing. No plugs so I'm lucky this one has not seized. Villiers magneto firing 2 cylinders at the same time. Coil could well be dead. Full strip and rebuild required. Nice brass or bronze prop. I'm very happy
First task is apply WD40 to all fasteners, and do some research. AMAL throttle lever same as SD fitted, wonder if this was original?
It seems that the later tank with flywheel in the middle was introduced around 1948-1950 (BMB Swordfish). So unless BMB made the later model at the same time then this engine might be pre 1950.
Does anybody have any literature or photos of BMBs similar to this one? Also any BMB history buffs around?
Hello Oyster - as you say, this model pre-dates the Swordfish - these motors are difficult to date, but I would say this one is from the late '30's into the wartime period.
At this time they were still made by BMB - the Swordfish - which I think started in 1948 were made in Southport by Brockhouse Engineering, who had a go at most mechanical things in their time including the wartime pratroopers' Corgi or Wellbike.
Brockhouse promote the BMB moniker as 'British made by Brockhouse'.
I don't know why these engines aren't more popular - they put out a true 4 HP and are well engineered - the achilles heel seems to be that the cylinders rot out.
I believe production started in 1932, where the earlier engines had the same box exhaust but with fins on the rear, and had a chromed tube as a tiller which could be pushed out of the rear of the engine when it had been swung round to provide reverse. They also had a chromed gearcase and propellor - cooling varied from the vacuum system as on some Anzanis, through a force feed via a horn behing the prop - later engines had a more usual pumped system.
These motors aren't common - probably quite expensive in their day - but they do come up on ebay periodically.
Hi rick, thanks for the thoughts. I suspect that dating this one will an estimate at best. There are some photos on the net of an original middy that has the same tank powerhead and throttle lever, supposedly mid 1930s. This one has the very same brass plates on the tank telling the user how to mix fuel etc. so your suggestion of mid 1930s to 1948 sounds about right. Great engines, but quite heavy compared to a 102 of similar up? I've also got a swordfish that I've not picked up yet.I'm away with work at the moment, so more investigation to follow.One thing to note this one does not rotate 180 degrees?
Groping in the old memory box now, but I'm fairly certain they all rotated for reverse, and there is a reverse lock behing the drive tube near the top, which automatically engages/disengages - is your seized perhaps?
Yes they are heavy but they are a twin of aorund 150cc's so should put out 4HP to compare with an optimisitic 2HP from a 102 in spite of the claims.
The later Swordfish went to 5 HP which I think was a consequence of a ground out carb inlet tract and the fact they had automatic ignition advance (cable operated between the magneto baseplate and throttle)
I know of an outboard dealer who could get a light boat on the plane with a Swordfish!
After looking more closely I've spotted a spring load plunger behind the transom bracket, this disengages the lock and allows the powerhead to rotate 180 degrees to give reverse. Thanks Rick.
A bit more research and I discovered this advert showing the swordfish style tank dated 1946. So this engine I have is potentially pre 1946. Intriguing! The remains of a tank logo has the same address on it.
Nice motor, my kind of project, I do like the apposed twins, I have three, the CV, ok its a four stroke, that runs well and two junkers, a 1946 Elto twin and a 1937 Johnson 210, with one rusted out cylinder, but other than that its complete, with spark.
Its a shame parts are so hard to get.
The BMB looks pretty complete, which is a good start.
Yes, I've seen these. My Britannia has exactly the same powerhead. Only things missing are the fuel tap and a water tube. It looks like the coil is defunct, which is probably why the engine got left in a shed. I'm pretty chuffed to have this one, think it might be the next project when the featherweight I'm currently giving the full treatment to is finished.
Thanks, that does narrow it down a little. I wonder when the finned exhaust was discontinued? This engines seems to be between whenever the "square" exhaust came in and circa 1946. All interesting stuff. Once I strip it down their may be some numbers to investigate.
£25 was a lot of money in those days. But a fairly sophisticated motor I suppose for it's time. The cooling system is fairly intriguing - Forced by the prop up the leg and then cooling the exhaust and cylinders. There does not seem to be a tell-tale either. How would you know if the water flow was blocked?
BTW ... !'ve got lots of spares for these motors as I've been collecting lots of dead ones for a while now. So if BTW you think you're stuck ... you probably aren't.
Thanks chris, I'll be making a start on this one as soon as I have tidied up some loose ends on some other projects, so I will be in touch.
I do need an alloy magneto cover, same as the one fitted to the midi, and also the original push/pull fuel tap. However I have to strip and understand the engine first, work out the date etc.
I've now started stripping this engine, to get a feel of the condition etc. The engine number is OB/1246/9. Any ideas how that can relate to a year of manufacture? There is some resin type material on the skeg, but overall the condition is sound. The coil seems to be dead, but the magneto is fairly typical condition for the age of the engine.
It looks like the crankcases and bottom end have been painted silver previously, wonder if that is original.
Before I go any further I will clean and refurbish the carb, silencer, prop and tank and put them to one side. Prop is excellent, heavy bronze example, with a brass shear pin driving it. The tank has some damage that needs repair.
The cooling system consists of the prop forcing water up the leg, which is then split to go around the cylinders and into the exhaust. That could explain why these engines are often seized, as water could very easily get into the innards of the engine, particularly if the engine is tipped before the water in the exhaust drains away.
More to follow as I learn more. I'll certainly be talking to Chris.
That's the inboard version known as the mariner. Same power head, but coupled to a reduction gearbox and fitted with an output shaft. Under dirt it looks like it could be ok. Different magneto to the one I have, but I think it is the same as the swordfish. 1950s I think.
I'm surprised they didn't make an industrial version also,a as it could have been palletised driving a pump or a genny etc.
Pretty much complete and still turns, but a bit tight. A couple of water pipes and fuel tap missing. No plugs so I'm lucky this one has not seized. Villiers magneto firing 2 cylinders at the same time. Coil could well be dead. Full strip and rebuild required. Nice brass or bronze prop. I'm very happy 
