Running a two stroke from a large static tank? How to deal with mix?

[CaptainRivet]

Originally Posted by Franziska

Just checking for now.



We might have a chance to get two new Tohatsu 9.8 two strokes. Hailed by many as one of the most robust engines around. Simpler than the Yamahas, easier to fix or get fixed in remote places.



I just learned that it's very difficult to get parts like the CDI unit for the Yamahas in some non first World countries. Takes a lot of money and even more time to get such.

Thankfully we had a second engine (in some locations you need to motor a few miles before you can sail).

The other is that mechanics in this type of places are much more familiar with the less complicated two strokes.





Much lighter than the Yamahas.

We could even get a third one for the dinghy. So three identical engines on the boat. One fails and you still would have the dinghy one which you can mount in its place.



Still there is the inconvenience with the mix.

Regarding letting premix sit, that's exactly what I would like to avoid. Have the main tank as normal and mix in the oil thereafter.



Maybe you are right and we need some sort of daytank for each of the two engines. The stupid thing is the fuel transfer would nessecitate it to install a big pipe to be reasonable fast.



No saying we go down the two stroke route, but its worth a thought.

Plus they are so light you can even check them in as normal luggage on a plane.

[vk4hr]

If its a boat, it will be shaken, not stirred.
But seriously, premix in smaller volumes and then add. You caN also add the oil and when the fuel is added via a nozzle, it should see good mixing.

[Nicholson58]

[QUOTE=Franziska;3889276]Thanks. We are talking of fifty gallon. Occasionally this tank might sit for a number of weeks unused, which might lead to separation of oil and petrol. You can't simply stir it then, hence the question.


The external system should essentially create the Premix on the go, injecting the oil into the fuel line between tank and engine.

We usually give the small outboard tank on our dinghy a short shake before starting up.

Still, I'm not talking about the dinghy out boards above..[/QUOTE


The 2-st oil is totally miscible in gasoline. It will never settle out. It’s like salt dissolved in water. Mix the oil in the fuel jerrycan and transfer to the 50 gallon or add oil to the 50 and top with gasoline. No problem, don’t overthink this.

BTW, I recommend an in line fuel filter with a water separation and drain bowl.

[Don C L]

Probably a good idea to add something like Sta-Bil to treat the gas since it will likely be sitting for long periods of time. I have only have 2 6-gallon tanks and it takes me forever to burn through it all.

[Statistical]

I wouldn't run it off 50 gallon tank. Have a 50 gallon tank and a 5 gallon day tank. Add mix to the day tank.

[MikeHoncho]

Oil is miscible in gasoline and will not separate. Ethanol can over a extended amount of time but being that it is usually less than 10% of the volume, it isn't a issue. Worry more about the gas going bad......

[Tupaia]

I ran 2 x inboard 2 strokes for 10 years, using 4 x 60 litre fixed tanks. Never had a problem with fuel. Much less hassle than the diesel I now have. I always mixed in jerry can before adding to the main tank to ensure correct ratio. It is easy to forget where you are when dealing with large quantities. This was before "bio" however so things may have changed. I know that "bio" diesel is a real pain.


The Tohatsus are brilliant engines that exist in their thousands outside of Europe but I am not sure they will deliver the same thrust as the Yamahas and will use more fuel.