Saving Old Seagulls

Hi all

I have inherited my father’s old Britannia Swordfish that he bought brand new when he was at college. Can someone please confirm the oil mix ratio please?

Many thanks
Neil

According to the handbook, the fuel mix is 20:1 and they recommend either:- Castrol XL, Essolube 40, Motorine C, Triple Shell or Mobiloil BB (don't know if any of these are still available).

Ferrier120 wrote: Sun Apr 06, 2025 4:37 pm According to the handbook, the fuel mix is 20:1 and they recommend either:- Castrol XL, Essolube 40, Motorine C, Triple Shell or Mobiloil BB (don't know if any of these are still available).

Thank you very much. 20:1 TCW3 it will be!

I’ve now had the motor running in a drum. Initially it only ran on one cylinder, so I replaced the old Champion 8COM spark plugs with a new set of D16’s, set the points, and it started second pull and ran smoothly. It does however give the occasional back fire, as though the ignition momentarily completely cuts out then in again.
One thing that I noticed is that the cylinder heads get very hot; too hot to touch with bare hands, and any splashes of water on there quickly evaporate. There is a good strong stream of cooling water coming from the tell tale, and possibly a similar amount exiting with the exhaust. I also loosened the cooling pipes from the cylinder and confirmed that there was water flow.
Is it normal for these engines to get this hot?

Those familiar with these engines will note that the original rope starting mechanism has been replaced with a recoil starter (by my father).

Thanks
Neil

The cylinder head is not water cooled, only around the sides of the cylinder, so yes, the cylinder heads will get hot.

If you hadn't mentioned that your father had installed the recoil start, I would have thought it was an optional extra that I wasn't aware of and had been fitted at the factory!

Ferrier120 wrote: Fri Apr 11, 2025 4:43 pm The cylinder head is not water cooled, only around the sides of the cylinder, so yes, the cylinder heads will get hot.

If you hadn't mentioned that your father had installed the recoil start, I would have thought it was an optional extra that I wasn't aware of and had been fitted at the factory!

Thanks for the info. Any suggestions as to what might be causing it to backfire?

I think it may pay to double check a few things, making sure the carb is still clean, then all contacts on the ignition system are clean and have good connections.