Saving Old Seagulls

Most lubricants for manual gearboxes and differentials are hypoid gear oils. These contain extreme pressure (EP) additives and antiwear additives to cope with the sliding action of hypoid bevel gears.

It is extremely important to note that EP additives are corrosive to yellow metals such as copper or brass in bushings.
I've still get a gallon of the old Hypoid90 and still use it on some motors.

I found this.

Certain types of EP additives are designed to react with metal surfaces under elevated temperatures to protect them under boundary lubrication conditions. These types of additives are often referred to as “chemically active”, and at elevated temperatures (greater than 140 to 150 F), they can indeed start to react with yellow metals. For this reason, apply caution when selecting gear oils for worm drives; the ring gear is often a yellow metal alloy.

A good way to check to see if an oil is “chemically active” is to look at the specification sheet provided by the lubricant manufacturer. On the sheet, you will typically see a test referred to as “copper strip corrosion” (ASTM D130). This tests how chemically reactive an oil is to copper and copper-containing alloys. For gear oils, a 1a rating is typically a good indicator that the oil is chemically inert, while higher ratings (such as 1b or 2a) might indicate possible problems when used in certain gearing at elevated operating temperatures. Often, a lubricant manufacturer will specifically state “this oil should not be used in gearboxes containing yellow metals”; other times, the manufacturer will simply state that the oil is appropriate for “steel-on-steel” applications – the implication being that they should not be used in situations where the ring gear is brass or bronze.

Have stuck a brass rod in my gear oil to see if it tarnishes.

I am sure the emulsified sea water will be more corrosive at the sort of temperatures found in seagull gearboxes.

H-A

I don't know zip about these outboards but yeah hypoid lube can be hard on yellow metal in a high temp enviroment which is a concern in car/truck transmissions with brass synchro rings etc but they operate at a LOT higher temps than the water logged gear box in a seagull. As H-A said the seawater is prolly doing more harm than the incorrect lube oil.

Valvoline make SAE140 Gear oil for truck gear boxes, I bought 20Liters for $60 about 10 Yrs ago, probably last my life time.

penrite make transoil 140 gear oil, a no additive gear oil used in vintage cars and perfect for seagulls

I think we can safely say is that the warmest your lower unit is ever going to get is in the shed on a hot summers day maybe 25 degrees c, unless you leave it in the sun in the back of the car.

At these temperatures EP / SAE is not going to make any detectable difference.

So if you can get SAE use it, if not, use EP & don't worry about it.

Anyway how many of us have a Seagull that was used for more than 10 hours last year?

I'd guess that less than 10% of our Seagulls do more than 5 hours a year, except the Kiwi Waikato racers who with testing & racing might do 20 hours.

Reardless of what Chrysler may or may not have said I rely on British Seagull's advice. Suffice it to say that I have a bottle of EP140, still bearing its original British Seagull label.

Charles is perfectly correct about the temperatures.

Use EP 140 with confidence

Manifold

Brass/bronze components are prone to corrosion when at elevated temperatures in the presence of moisture (in theory at least). In practice such 'corrosion' seems to be confined to items under the specific condition of high point load such as gear-sets & worms. Low point load items such as thrust washers & syncros seem indifferent. My EP90 dispenser pump is over 35years old & the brass bits look like new.

My experience of seagull gearboxes is they are quite tough if looked after. They die from corrosion from water ingress. Never seen a well serviced box wear out, regardless of the oil type, mineral, synthetic, EP, vegetable, or whatever. Even seen diesel used once. When selecting lube oils for jobs, I tend to look past the manufacturers selective recommendations. I prefer to carefully consider the application & make careful choices that are in the end users best interests. Saved alot of unnecessary cost & re-builds

Suggest the question is not so much what type of oil, but, moreover how often is it changed. Reminds me of the courier who thought timely oil changes on his diesel were unimportant. Cost him 2x major engine re-builds, then his entire business. He blamed it on the oil, rather than his non-existent maintenance program.

Rex