Anyone know anything about Gemini outboards?

[neale]

Purely for the joy of tinkering, I really don't need another outboard, I saved a Gemini 3 air cooled outboard from going to the scrap man. Spent today giving it the once over and cleaning out the fuel system in readyness for trying to fire it up, possibly next weekend.

Does anyone know what the fuel/oil ratio would be? I am thinking probably 50:1 but someof these obscure older outboards used 25:1 IIRC.

 

[VicS]

Purely for the joy of tinkering, I really don't need another outboard, I saved a Gemini 3 air cooled outboard from going to the scrap man. Spent today giving it the once over and cleaning out the fuel system in readyness for trying to fire it up, possibly next weekend.

Does anyone know what the fuel/oil ratio would be? I am thinking probably 50:1 but someof these obscure older outboards used 25:1 IIRC.

Not heard of a Gemini outboard

50:1 possibly if it is more recent than say the late 1960s other wise almost certainly a more oily mix. 25:1 maybe even oilier maybe. Seagulls ran on 10:1 until the late 1970s and from then on 25:1.

Much depends on the type of bearings . Only those with ball races and needle rollers can really be run safely on 50:1.
With plain bearings like Seagulls the oil was relied upon to form the seal as there were no seals fitted to the crankshaft.

 

[Rigger Mortice]

If you post a photo somebody may recognize it. It may be re-badged.

 

[neale]

This isn't mine, this one is a 4.5 and the only pic I can find on the whole wide web! Mine is a 3 and looks the same but with a different colour scheme.

Inside the lid there is a moulding mark that indicates it might be from 1985.

 

[Rigger Mortice]

Try searching on "Mac 3" or "Aspera"

 

[neale]

Try searching on "Mac 3" or "Aspera"

Thanks for that.

I tried Aspera and didn't really get an answer, although it is possible that the actual engine may be made by them.

Mac 3 threw up a few links to chainsaws and the like but I am still no nearer finding out the correct fuel/oil ratio.

Anyone know anything about these. Seems I have a very rare beast indeed.

 

[VicS]

Almost all, if not all, outboards were running on 50:1 buy the mid 1980s... some even on 100:1.

Digging around Mac 3 came up with 25:1 although year not mentioned

I would have said 50:1 for any mid 80s engine would be a safe mix but with the snippet about the Mac 3 I think I would go with 25:1 initially. If the plug tends to oil reduce the proportion of oil until it doesn't.

Heavens knows what the correct plug is though or what the gap should be.

Cd ignition or points ?

Oil type? Probably a TCW3 outboard oil but that is really for water cooled engines. I'd be very tempted to use an oil for air cooled 2 stroke motor cycles or garden machinery.

There is BTW a good chance that the exhaust is water cooled, water being deflected into a scoop behind the prop. Prolonged running with no exhaust cooling might damage any rubber mountings in the steering swivel/ mounting bracket. It happens to the old air cooled Volvo/Crescent/ Archimedes engines I am told.

 

[neale]

Amlost all if not alloutboards were running on 50:1 buy the mid 1980s... some even 100:1.

The digging around Mac 3 came up with 25:1 although year not mentioned

I would have said 50:1 for any mid 80s engine would be a safe mix but with the snippet about the Mac 3 I think I would go with 25:1 initially. If the plug tends to oil reduce the proportion of oil until it doesn't.

Heavens knows what the correct plug is though or what the gap should be.

Cd ignition or points ?

Oil type? Probably a TCW3 outboard oil but that is really for water cooled engines. I'd be very tempted to use an oil for air cooled 2 stroke motor cycles or garden machinery.

There is BTW a good chance that the exhaust is water cooled, water being deflected into a scoop behind the prop. Prolonged running with no exhaust cooling might damage any rubber mountings in the steering swivel/ mounting bracket. It happens to the old air cooled Volvo/Crescent/ Archimedes engines I am told.

Thanks for the info, some good pointers there. Never having owned or used an air cooled outboard before I hadn't thought of using a different oil or the possibility of the exhaust needing water cooling.

I think I'll do as you suggest and start with 25:1. As for the plug, luckily there is one with it so I'll have to assume it's the right one with the right gap.

The engine has CD ignition.

 

[Pete54]

I have a feeling the MAC and Aspera are 1960s designs. They appear to have a lot of similarities with the JAP and JLO engines. Both of those date from around the same period and are 25:1.

They seemed very modern at the time given that Seagull were still running 16:1 up until the early 1970s.......

 

[VicS]

I have a feeling the MAC and Aspera are 1960s designs. They appear to have a lot of similarities with the JAP and JLO engines. Both of those date from around the same period and are 25:1.

They seemed very modern at the time given that Seagull were still running 16:1 up until the early 1970s.......

Seagulls ran 10:1 until 1978 then 25:1. Post 1967 they can generally be converted to 25:1 but it is not recommended for earlier ones as they have different ( smaller ?) bearings.