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Couple of questions - Outboard motor

JayCbee

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18 Jun 2020
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Couple of stupid questions (where else do you learn other than forums and youtube!) -

I have a reconditioned Mariner 50 bhp 2 stroke for our 16 ft craft. Picked it up and the outboard place told the wife to put 500ml of quality oil into a 22l tank. We are novices but isnt the ratio 50-1 so it would be 440ml ? Or are we over thinking it and its OK to be a little over or a little under and its just a rough guide.

I was just going to use the 50-1 ratio depending on how much petrol we put in - So 10l = 200ml oil? , 20l = 400ml oil etc.

Also

She was told to not leave petrol in the outboard if not using quite a bit - at the moment its going to be running 2x a week at least so not a concern. Obvious question but I assume you simply disconnect the tank and let the outboard run out of petrol and thats the way to do that? Also when not in the boat should you disconnect the tank - is that best practice?

Be gentle with your replies!

I have a separate Depth Transponder question which Ill post separately

Apart from that the two novices finally launched yesterday at Conwy Marina after a very stressful day!
 

julians

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Some outboards are 50:1,others are 100:1,so you'd need to find out the correct value for your engine. But if the place you bought it from said 500ml for a 22l tank then it sounds like a 50:1 engine. Better to put too much oil in than too little, if you put in more than needed it'll smoke a bit more than it should and may foul the sparkplugs more easily.

You don't have to be super exact with the measurement of how much oil to add. So your correct with calculation onyour examples assuming it is a 50:1 engine.

I presume you're aware that you should be using 2 stroke oil and not generic engine oil?

And yes that is how you empty an outboard of fuel, well its how I used to do it anyway.
 
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BruceK

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oil ratio in the older two strokes is not a precise affair. A little extra just smokes a bit more and leaves a bigger oil slick behind you. Better a bit too much that too little.

As for lengthy periods away it's not really adviseable to run the carb dry as that leans out the engine and starves it of lubrication. You have a drain screw on the carb float bowl for that. Far more efficient as actually running the carb dry doesnt actually empty the bowl of fuel and can exacerbate gumming deposit buildup
 

BruceK

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Some outboards are 50:1,others are 100:1,so you'd need to find out the correct value for your engine. But if the place you bought it from said 500ml for a 22l tank then it sounds like a 50:1 engine. Better to put too much oil in than too little, if you put in more than needed it'll smoke a bit more than it should and may foul the sparkplugs more easily.

You don't have to be super exact with the measurement of how much oil to add. So your correct with calculation onyour examples assuming it is a 50:1 engine.

I presume you're aware that you should be using 2 stroke oil and not generic engine oil?

And yes that is how you empty an outboard of fuel.

Suzuki and Yamaha do 100:1 up to 30hp. 50:1 is the ratio for Mercury Mariner

However the OP said his OB was rebuilt. Depending on the rebuild he may want to rebed the engine on a mix of 25:1 for 4 - 8 hours and change plugs after he's done. They will foul.
 

JayCbee

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18 Jun 2020
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thank you for the reply its definately a 50:1. - yes we have the correct 2 stroke oil as recommended by the Outboard guys. Looks like he is going for the little bit more than too little approach with the 500ml in the 22l tank (bearing in mind we probably only went to 21L with the fuel. Ill try to be as accurate as we can be and certainly will put at least the correct amount in. Will never put 'under' the 50:1 ratio.
 

JayCbee

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18 Jun 2020
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thanks for replying - Ill find that tonight - what constitutes lengthy periods away by the way? If we are running once a week dont worry about it? Also the disconnecting the tank question - OK to leave the tank connected or best to always disconnect? thanks
 

julians

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I'd say you should be OK leaving it with the fuel in for a couple of months, possibly even longer.

I used to disconnect the fuel line and take it home with me whenever I left my boat, but that was more an anti theft deterrent than anything else.
 

BruceK

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Lengthy periods away very much depends on the climate and conditions allowing the fuel to evaporate in the carb. It generally makes them hard to start but old 2 strokes are amazing in that a quick squirt of petrol via a syringe directly into the throat of the carb will start most of them on the dime and run long enough to draw fuel. Longer periods away can leave unevaporated fuel in to get waxy and / or seperate with water absorption. Both have the tendency to clog jets and emulsion tubes with either wax gumming deposits or aluminium oxide salts (white sludge). This typically happens over winter periods so I wouldnt be too concerned until it comes to winter layup to drain the carb.
 

JayCbee

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18 Jun 2020
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Lengthy periods away very much depends on the climate and conditions allowing the fuel to evaporate in the carb. It generally makes them hard to start but old 2 strokes are amazing in that a quick squirt of petrol via a syringe directly into the throat of the carb will start most of them on the dime and run long enough to draw fuel. Longer periods away can leave unevaporated fuel in to get waxy and / or seperate with water absorption. Both have the tendency to clog jets and emulsion tubes with either wax gumming deposits or aluminium oxide salts (white sludge). This typically happens over winter periods so I wouldnt be too concerned until it comes to winter layup to drain the carb.
Understood thanks all for the replies
 

seastoke

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My boat is on the hard by the harbour masters office , it’s called Amanzi it has a black and white canopy help yourself to beer and Malbec out of the fridge.
 

BruceK

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Better believe it. You have to be married to one of my sisters before you can raid the booze box and AFAIK I only have one and she is not married.
 

BruceK

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We could however come to a possible arrangement on that score. Do you understand the customary practice of Lobolo? How many cows do you own?
 
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