Britannia

[Charles uk]

If the Britannia was a single cylinder you would have to put a stay on that to stop the vibrations work hardening the manifold section & fracturing it but if you've got a smooth running Mariner you should be alright.

It's lucky Dad supplied the brass & the silver solder as that stuff costs a fortune nowadays.

Looks lovely!

[pegasus*1760]

Thanks for your comments.

[Collector Inspector]

Same prop

9 1/2" x 8"

They hang around all over the place............

Cheers

B[/color]

[pegasus*1760]

Thanks for the info.

[pegasus*1760]

Does that mean you have a spare you are willing to part with.

[Oyster 49]

Managed to get some colour on the tank tonight..next bond on the brass plates, flat it all down, re mask and then a final couple of coats of colour. The colour is a little more blue than the original/blue/gray I think. The original paint was so faded though, so who knows? I've also got to get some decals made. It's never ending

I also re-assembled the cylinders to find both pistons still a little tight, and did not feel "Right" I'm sure sure what the condition of the rings is? The piston skirts seem to have evidence of some rubbing. Also at TDC and BDC the crank rotates left and right very slightly without the pistons moving. Not sure what to make of it. I've got a feeling that the rings are worn, causing the pistons to rub on the skirt. I wonder if new ones are available?

Interestingly these pistons do not have a locating peg to stop the rings rotating, so I suppose they must be fitted 180 degrees apart.

[Collector Inspector]

"I also re-assembled the cylinders to find both pistons still a little tight, and did not feel "Right""

I would check right now the internal dimensions of the pots for square and parallel . Use a bore guage and check everywhere down them. Sticking pistons that measure up well individually is of some serious concern. Forget rings as of now.

I would think that you have cleaned ALL of the rust from the jackets? Internal rusting does deform the block. This can be on the inside as well. The obvious is external which we all look for of course. Bore dimensions can be changed as well. Note that.

Remove the THREE plugs each block and check the waterways! Here.......... 1 and 2

And the third here...............

Minute check as above is the way to go aye?

Let us know how you go with that before running the Old Dear.

B[/color]

[Collector Inspector]

Does that mean you have a spare you are willing to part with.

Yes!

Not that one but another.

Has a small chip in it one blade.

It came from northern Can_nay_dee_ya...................it has been frozen often as well which does not help.

B

[Charles uk]

Is there a possibility that your not reassembling the same piston in the same bore it came out of?
These motors have pistons that are offset on the conrod so get odd wear patterns from the unconventional side thrust

When these were assembled there is a good chance that the piston was matched to the bore before it hit the assembly dept, as these weren't machined on computerised machining centres accurate to 10,000 of an inch, but by George on an old lathe with old fashioned tooling & fixtures.

Oyster what do you think was the best that George could achieve? on a mass production basis.

I've seen quite a few of these with cracked cylinders, the pistons came out with no problem, if they weren't held in by rust, in fact I have a crankcase, crank, rods, all the bits I needed in my workshop, as I was going to build a 2 cylinder Seagull as an April Fools Day wind up.
But gave up & carried on with my quest to build the fastest Seagull in the World, just as foolish!

I don't have a lower unit so can't confirm that the gear ratio is 2 : 1, as I planned to use a Seagull one.

[Oyster 49]

Yes, I did think about the cylinders actually being swapped over, but the symptons are same when the cylinders are swapped. I will measure the bores looking for wear/out of roundness etc. There is no sign of a step at TDC/BDC, in fact the bores look reasonable. When I cleaned out the water jackets there was a lot of rust ending up in a pile on my bench.

I do have a later swordfish that turns over beatifully, so I could use that as a donor for cylinders and pistons if push comes to shove. I'd rather not. Once I have measured the bores v piston diameter I'll consider what to do next. I've ordered a honing tool, which will probably clean up any highspots in the bores. However as they say, "measure twice, cut once"

[Collector Inspector]

"unconventional side thrust"

?

B

[Charles uk]

That's why conrods/little ends are normaly centered in the piston.

[Oyster 49]

Charles is right the conrods are offset in the pistons, these pics show the detail. The cylinders are also slightly offset on the crankcase. Quite a beefy bronze conrod, considering the cc is around 80cc per cylinder. I suspect these are quite a bulletproof bottom end.

[Collector Inspector]

Pistons are the same part number.

Piston checked measurements not dropping own weight in any bore means a problem.

Do not run until any issue is sorted.

Back to basics.

B

[pegasus*1760]

have just notice that there is a BMB BRITANNIA SWORDFISH for grabs on ebay restored by the vendors late father.