Johnson Outboard oil filler plug

[Keiron]

Trying to change the oil in the gearbox of an 8hp Johnson outboard. Can get the upper plug out without difficulty but not the lower one. It's extremely tight and now starting to get a bit damaged. I can't even shift it with an impact driver. Bit concerned about heating the aluminium casing with a blowtorch. Any suggestion? Any way of chenging the oil effectively without getting the plug out? All advice gratefully recieved....

Cheers Keiron

 

[VicS]

Very carefull heating with blowtorch, a hot air gun or even a powerful hairdryer, immersion in a bucket of very hot near boiling water.

Have you got a very big screwdriver, one with a blade as wide as the head of the screw with a handle to match and provision to turn with a spanner?

Those are my ideas for undoing it.

It'll be very difficult to change the oil without getting it out, the ususal practice is to fill from the bottom as well! You need to get rid of any water which will have collected at the bottom. If it is well mixed up and warm you might get most out slowly by lying on its side with the gearbox slightly raised but I doubt it.

 

[tross]

I would add to the above with, if you can get some freezer spray from your local plumber, once the lower leg is hot, spray the freezer on the filler plug.

 

[Keiron]

Thanks for the advice. Tried all the above and still won't shift.... It's incredibly tight.... I may have to strip the gearbox in winter to change the oil. Not ideal!

Cheers Keiron

 

[Lakesailor]

I just had a similar problem with the filler plug on the trim/tilt reservoir on my Johnson.
I went for broke and used my tried and tested Mini-engineering technique. Using a stubby cold chisel with a fairly blunt tip I tap the outer edge of the slot on the circumference in an anticlockwise direction. Sure, it may start to chew away the slot, but it is a last-chance method if you are prepared to buy a new plug. Just rember to try and get the force applied tangientially.
In this instance I was lucky and it freed off quite quickly. In your case the gearcase casting will absorb a lot more punishment than my reservoir can would have done, so you would be on a better bet.

If you don't have any mechanical sympathy, it may be a bit of a gamble

 

[VicS]

[ QUOTE ]
I may have to strip the gearbox in winter to change the oil

[/ QUOTE ] If it really comes to that then just removing the seal housing behind the prop should be all that is necessary but the two srews that hold that may be just as difficult to remove and more easily sheared off if too much force used. Replace the seals and the O ring at the same time.

Also you might just as well drop the gearbox off and renew the pump impeller. If it is still the original it is probably time it was changed. Then of course there are two seals below the pump on the drive shaft and an O ring around the gear selector shaft......!

I have not checked but if yours is a long shaft and is the same as mine it is vital to remove the extension with the gearbox rather than removing the gear box from the extension. The reason being a bush in the extension that the shaft will not pull through until it is cleaned up which leads to smashing the pump body if you do it wrongly!

 

[Keiron]

Thanks for the advice
K