Saving Old Seagulls

A curiosity.........

Sevice Sheet No. 13 " The seagull wide-ratio reduction gearbox" para 6 has the motor in a horizontal position, tank downwards, with the filler hole presented on top for refilling with oil to the normal service level. This seems a very natural and obvious position. It goes on to say that oil should be "topped up to a little below the bottom of the filler plug hole". No dimesions, exact depths or fill lines and this is left to the owner to decide what is "a little below"! Typical Seagull speak. Nothing new here then! There is a small shelf detail visible through the filler hole which is the rear propshaft bearing housing detail. This seems a convenient filling level which would leave some air in the gearbox.

Whatever the final level chosen, whether it is a half or threequarters of an inch below the bottom of the filler hole, the volume of oil used intuitively seems much greater than that where the motor is stood vertical and the oil is filled up to the bottom of the filler hole. The vertical motor method is the received wisdom from various web FAQ's. So I thought I'd measure the difference between the two methods for a newly acquired Silver Century and also record the actual volumes since they don't seem to show up anywhere on the web or the Service Sheets.

After allowing the gearbox to drain for 24 hours in very warm conditions it was refilled with cold water according to Service Sheet 13 to just below the rear bearing "shelf". This was a water volume of approx 235 ml. The drain plug was fitted and the motor placed vertically. The plug was removed and the escaping water caught in a tray. The volume draining out was 63 ml. This puts the "vertical" gearbox volume filling method at 235 - 63 =172 ml for a 1972 Silver Century.

There are web statements that assert clutch operation suffers if the gearbox is full of oil, or presumably when the remaining air is replaced by water. But where did the idea of filling to overflowing out of the filler hole in the vertical position originate since it is significantly different in volume to the Service Sheet? Quite a percentage difference but does it make the slightest bit of a difference in practice?? !!

I am not going to do an error budget for my measurements but simply caution "your mileage may vary". Value of the efforts above? Maybe not a lot but I now know that I should get approximately seventeen oil changes out of a four litre can of SAE140! With annual changes I'll be quite pleased if I can still lift the motor vertical at the end of the can!

If I recall the FAQ correctly, the gearbox is designed to leak some water in so that the 140 oil emulsifies and coats the gears during operation...if you overfill, for instance, by just filling up the gear box lying down, you probably cant get any water into the box to emulsify...

I confess I fill while horizontal, and then let the excess run into my oil drain pan at the beginning of each season....since I can buy the oil on the way to my launch site, I dont worry about running out..

I tend to fill gearboxs up to the filler hole,with the motor vertical this still leaves a air/water space,with seagulls method of oil/water mix lubrication the exact amount of oil is not that important,the correct grade of oil however is.

You are quite right about the early service sheets telling you to fill the motor whilst it was face down, filler uppermost. What they were very vague about was how full....

In later service manuals they clearly show the gearbox level as up to the lower lip of the filler hole with the motor vertical. Makes more sence.

there is a good reason for this.

Seagulls generally do not have oil seals. If you fill it any fuller it will simply seep out via the propshaft. leaving a puddle.

It is also correct that clutch models may not work properly if over filled, and it is also correct that they were designed to work on a mix of oil and water, but the level will stay the same or drop, as extra water will increase the interior level and it will simply drain out via the prop shaft again, but quicker now, as it is thinner.

Check and refill or replace every 10 hours use to be safe, especially on the Featherweights.... not a lot of oil in there to start with.

The older 102s had a different system and suggested using an oil pressure filler on the oiling nipples, till the oil was seen to be forced out by the prop shaft! The oil was possibly a runny grease more than a straight oil. Later 102's had the same filler on the cap as later models and the same regime, fill to bottom lip of filler hole when vertical.


the later gearboxes with lip seals are better if the seal is good, and you can use 90 grade oil, less drag I suppose. But as soon as the lip seals go switch to 140 till you replace the seals, if you ever do!

Regards,
John
SOS

>>" You are quite right about the early service sheets telling you to fill the motor whilst it was face down, filler uppermost. What they were very vague about was how full.... In later service manuals they clearly show the gearbox level as up to the lower lip of the filler hole with the motor vertical. Makes more sence."

So Mr. Williams, am I correct in inferring that I should disregard the instructions of the "old" service sheets for the Century Silver and fill the gear case of my Silver Century by the same method as I fill my Featherweight? (i.e. vertical, up to the lower lip of the fill hole?) Thanks.

Charlie in Maine, USA (still waiting for 20 cm of ice to melt on the lake....)
Open water fishing starts on April 1st. !!!

Hi Charlie,

Yes, unless you like the odd patterns the oil makes on the garage floor when it leaks out!

We have been basking in sunshine here, after a mild wet Winter, this time last year we had snow! They say it will be colder next week, but I bet we do not get 4 inches of ice!

Happy Seagulling, when it melts!

Regards,
John
SOS

In later service manuals they clearly show the gearbox level as up to the lower lip of the filler hole with the motor vertical.

Sound reply John; logical explanation. Obviously then I'm working from old documentation. This brings up another question. How do BS record a new issue of Service Sheet? By revision issue letter, date, or totally new Service Sheet Number ?

Peter

Hi Peter,

In the old British Seagull days they used to send out 'Dealer Data Sheets' with new information for dealers. This stopped by 1996.

The information in the leaflets changed too over the years, in an early one they advised using an 'air line' to back flush the water system. Years later it was realised that air would compress to get through an obstruction, so they changed that to 'use a garden hose'! Much more sensible, not every one had an air line to hand anyway!

Like wise with the gearboxes, early ones were filled till it oozed out the shaft! With pressure oilers! Then it was lay down and fill to bottom of filler, but noone knew where that level was..... and it was cetainly more than half full, so they leaked the excess out!! In later handbooks the level we use now appeared, to the bottom lip of the filler hole when upright.

cheers,

john
SOS