Problem changing gear lube on Mercury 3.3hp 2-stroke

[bacoms]

I'm trying to re-commission my Mercury 3.3hp 2-stroke outboard that has been laid up for the last 5 seasons.

All was going well until I came to change the gear lube. I drained out the old oil (which had the look of fresh oil with no signs of water ingression) but cannot for the life of me squeeze fresh oil up to the overflow hole. I manage to get a small amount of oil in but it refuses to go any further. Net result: little oil in the sump, a lot of oil over the floor.

Does anyone with experience of these engines have any thoughts on what the problem could be?

Many thanks,

Bryan

[MoonSailer]

put the lower screw in and tighten. Put oil into the upper screw hole until full. Put in the upper screw and tighten.

[negrini]

Yeah, this is against what the 3.3 manual recomend, but I also found it far easier although you'll not fill completely, but with some patience ....

[Omatako]

When you pour oil into the top hole, lay the motor on it's side, alternately pour oil in and stand the engine up until the oil starts to trickle out when standing up.

Otherwise you'll either fill the whole gearbox and that's not a great idea or you'll struggle like hell to pour the oil in.

[bacoms]

My thanks to Moonsailer, Negrini and Omatako for your replies. Tried all your suggestions them to no avail.

It would appear that there is a blockage near the overflow hole. I removed the prop-shaft housing and examined the interior. All nice and pristine. Then hooked up the lube pump to the overflow hole and tried to squeeze some lube through. No joy. Tried poking around in the hole with a thin length of plastic but couldn’t get past the first 20mm or so. (could be because there’s a right-angle turn at this point.)

Then tried to remove the lower section completely from just above the overflow hole and managed to shear off the first of the 2 bolt I tried to undo. (Why do they use such crap bolts etc when decent ones would only cost a few pennies more?)

While I’m drilling out the thread, can anyone throw any light on what the problem could be and what I should do to fix it?

Many thanks,

Bryan

[14432]

Just to be sure - when you're trying to fill via the bottom hole, you do have the top screw out, correct? Otherwise, there's no place for the air to go.

[tommays]

If you cant force air out of the vent YOUR not going to be able to pour oil in it no matter how slow you go

I have to think there is some mistake with the plugs going on as without removing the vent plug the oil takes a very long time to even drain ?

[MoonSailer]

I actually pumped the oil into my top hole. I had little success trying to fill from the bottom hole. I could not get a great seal . Sorry that you are having so much trouble. Temperature can be important heavy oil is hard to pump when cold.

[pvanv1]

If the lube drained OK with both plugs removed, then there is no reason why it can't be pumped in from the lower hole, again with both plugs removed, unless some debris is acting as a check valve at the top hole.

Standard method, with motor upright, is to pump in from below until it overflows the upper hole, then install the top plug (which will create a vacuum when the pump is removed), then remove pump or squeeze tube from lower hole and reinstall lower plug quickly, before more than a couple of drops make it out.

Attempting to fill from the top hole is really nearly impossible due to trapped air preventing lube from going in. Unless of course you use a hypodermic type injector, a few drops at a time.

[timebandit]

The top hole may be just a small vent hole so your probe might not go through.

You might have your tip on the filling device to long so that the tip is touching something inside and blocking it's flow from the bottom.