Saving Old Seagulls

I've jut got another silver century and have found that the gearcase is filled full with what appears to be grease. It will not run out of the plug but is not as thick as normal grease. I'm assuming it is grease that has lost its viscosity through use. Should I renew it with 140 gear oil or will it be ok left in. Thanks

The British Seagull Service Manual is very clear on this point in the section titled:

"The Seagull Wide Ratio Reduction Gearbox , Its Charteristics, Lubrication, and Maintenance"

It states "UNDER NO CIRCUMSTANCES MUST GREASE BE USED" (their emphasis, not mine)

It is likely to be emulsified oil. Mine looked the same after long turm use in seawater and lack of use for a few years. Fill up in normal way with 140 and carry on regardless
LLS long shaft

Had another look at my gearbox and it does more like grease. Took the cover off and found old grease put in by the original owner - me putting oil in over the months had weakened it a little. Now cleaned up and awaiting new gasket but it may be that the grease was to hide a leak.
So my advice is to do the above

take the cap or end off where the 2 screws are, soak the screws and heat them if they are stuck, I also use one of those vice grips on them, don't know what they are called over your way, dig all the grease out with a screw driver or whatever,if you run the gearbox on grease the top pinion and bush doesn't get any lubrication, the gearbox always leak in the older one as there are no seals.
its an easy job to clean it out like virtually everything else to do with seagulls