Which oil for 6hp 4 stroke gearbox

[Gitane]

I need to change my gearbox oil on a 6hp mercury 4 stroke outboard.

The only gearbox oil I can find is SAE 90 which on the tube says it is only for 75hp and upwards engine.

Which oil should I use on a 6hp engine, and would SAE 90 do?

Gitane

 

[sailorman]

Do not use the sae 90 in the engine it would be more like a 15/40

 

[VicS]

A premium grade 80W-90, or similar, outboard gear oil, rather that a high performance grade SAE90 oil

and
A 4 stroke outboard engine oil. 10W-30 or as recommended in the owners manual for the engine.

Mercury owners manuals avaialble from the Brunswick Marine in EMEA download center: http://download.brunswick-marine.com/download/

Quicksilver is a good brand and widely available

 

[Gitane]

Thanks for the advice.

Looks like SAE 90 is Ok for gearbox according to manual. Not sure why quicksilver bottle says it should only be used for gearboxes of engine with 75HP or more.

Gitane

 

[VicS]

Thanks for the advice.

Looks like SAE 90 is Ok for gearbox according to manual. Not sure why quicksilver bottle says it should only be used for gearboxes of engine with 75HP or more.

Gitane

Quicksilver do two grades: the bog standard grade which is "Premium" grade with a viscosity of 80W-90 for lower powered engines and a "High Performance" grade, which is an EP 90 oil, for higher powered engines. IIRC the two should not be mixed.

You could use an automotive EP 90 oil but it does not contain the additional corrosion inhibitors and emulsifying agents to guard against the effects of water intrusion that the outboard oil gear oil does.