outboard lower leg filling with oil

[dylanwinter]

the instructions for the Tohatsu 6hp sail drive call for the oil in the lower leg to be replaced once a year

it tells you to remove both plugs - drain it all out and then replenish it from the bottom up

you are supposed to squirt oil upwards through the lower filler until it emerges from the top and then screw the lower plug in without spilling any

what is the engineering sense in this?

Dylan

 

[prv]

Dunno, but it's standard practice. Possibly something to do with avoiding trapped air?

The normal gear oil is pretty viscous, so it's not as daft as it sounds to try to put in the bottom plug without losing it all. Putting in the top plug first will help hold it in.

Pete

 

[Talbot]

This method really works!

When the oil appears out of the to screw hole, put the top screw in and tighten, then when you remove the tube at the bottom you will lose very little oil.

 

[wotayottie]

the instructions for the Tohatsu 6hp sail drive call for the oil in the lower leg to be replaced once a year

it tells you to remove both plugs - drain it all out and then replenish it from the bottom up

you are supposed to squirt oil upwards through the lower filler until it emerges from the top and then screw the lower plug in without spilling any

what is the engineering sense in this?

Dylan

Avoiding the airlocks that can and likely would ocurr if you filled from the top. Gearbox oil is viscous and easily forms bubbles

 

[VicS]

the instructions for the Tohatsu 6hp sail drive call for the oil in the lower leg to be replaced once a year

it tells you to remove both plugs - drain it all out and then replenish it from the bottom up

you are supposed to squirt oil upwards through the lower filler until it emerges from the top and then screw the lower plug in without spilling any

what is the engineering sense in this?

Dylan

Yes it is the way it is done.
And it can be done making less mess that attempting to fill via the top hole

It ensures that no air pockets are trapped.

*Get a squeezable bottle of outboard gear oil with a tapered nozzle that will fit tightly into the drain hole. When it is MT keep it and refill from a larger can.

I fit the top plug first then remove the bottle and fit the bottom one.

New seals on the plugs are advised .. It is said that leaking seals on the plugs is the biggest cause of water ingress........ I'm still using the originals after 27 years

Warm the gear box before draining it and warm the oil slightly before refilling to aid the flow

* if you want you should be able to buy a pump that will fit the drain hole in your engine.

 

[pampas]

Always thought it was to leave an ullage for expansion.?

 

[VicS]

Always thought it was to leave an ullage for expansion.?

Well yes that is why they are not completely filled, but the position of the level plug ensures that it is filled to the correct level.

 

[VicMallows]

After replacing the top screw (with the o/b vertical), why not just tilt/lay-down the engine before removing the filler nozzle? OK, only possible on smaller, removable o/b's.

 

[Billows]

How come you don't have to change the oil in a car gearbox every year?I have never seen an outboard with worn gears?They are pretty agricultural and over engineered.The oil always comes out yellow, clean and pristine unless the seals fail.

 

[neale]

How come you don't have to change the oil in a car gearbox every year?I have never seen an outboard with worn gears?They are pretty agricultural and over engineered.The oil always comes out yellow, clean and pristine unless the seals fail.

Because a car gearbox doesn't spend its time in salt water. Changing the oil is the only way you are going to know that a seal has failed and that water has got in to the gears.

 

[VicS]

After replacing the top screw (with the o/b vertical), why not just tilt/lay-down the engine before removing the filler nozzle? OK, only possible on smaller, removable o/b's.

You might be able to do that with small outboard but not with an awkwardly shaped lump weighing 1/2 hundredweight while holding the oil bottle in position with one of your extra hands.

Anyway once you have laid it down the oil bottle will be upside down so oil will run from that once you pull it from the gearcase filler hole.

There really is no problem filling an outboard gearcase in the recommended manner!