# Problem changing gear lube on Mercury 3.3hp 2-stroke



## bacoms (May 20, 2009)

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 (Jun 1, 2007)

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


----------



## negrini (Apr 2, 2008)

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 (Sep 14, 2003)

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 (May 20, 2009)

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 (Oct 24, 2006)

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 (Sep 9, 2008)

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 (Jun 1, 2007)

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 (Nov 16, 2007)

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 (Sep 18, 2002)

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.


----------



## RanAweigh (Jan 16, 2009)

Are you using a pump such as this one?









The threaded end is designed to thread into the plug hole. If you are trying to squeeze the bottle with the dunce cap top stuffed into the hole, as another poster has said, you may be blocking the path.


----------



## timebandit (Sep 18, 2002)

mecury part sex press   

I thunk we did not allow those kind of sites here:laugher :laugher :laugher


----------



## RanAweigh (Jan 16, 2009)

Why not? There was a whole thread about a coffee press.


----------



## bacoms (May 20, 2009)

Thanks for all your replies. I really appreciate it.

I've made some progress by cleaning out the top hole with a cotton wool bud then blasting some GT85 into the small hole inside while poking around with a fine piece of wire. After a while the GT85 started to disappear and eventually dribbled out into the gear housing (that I had taken the cover and prop shaft off earlier). 

I then screwed the lube pump into this top hole and slowly started to pump, stopping once I'd built up some pressure. After a minute or so a continuous dribble of lube oil arrived at the gear housing.

The question is; is this dribble the normal flow rate one would expect indicating that the blockage has gone or is it still partially blocked? I seemed to remember that when I used to fill from the bottom hole (using those tubes of lube with the plastic nozzle) not a lot of pressure was required before the oil appeared at the top hole. 

A neighbour who's much more mechanically minded as me, suggested screwing a grease nibble into the top hole then trying to force some light oil in. I might take him up on that idea. I'll feel much happer when I can see a steady flow of oil under fairly light pressure.

Cheers,

Bryan

P.S. I see Adewall in thread 'Mercury 3.3 Lower Unit Maintenance Question' seems to be having much the same problem. I'm not sure I like his repair shop's approach of opening the gear housing and filling it with oil that way with the blockage still in place.


----------



## bacoms (May 20, 2009)

RanAweigh said:


> Are you using a pump such as this one?


Similar but not quite. The one I'm using is this one at Seamark Nunn Limited Gearlube Pump Kit - Suits All Engines


----------



## bacoms (May 20, 2009)

I thought I'd better complete this thread to show my appreciation to those who took the trouble to reply and to help anyone else finding themselves in a similar situation.

After buying some quality 3mm drill bits, I finally managed to drill out the body of the bolt that snapped. This was the aft one of the two holding the complete lower section (gear housing and prop shaft) on to the unit.

Having got this far I though, what the hell, in for a penny, in for a pound and gingerly undid the other bolt. Typically this came off with no trouble at all. I then eased off this lower section which enabled me to give everything a good clean (it wasn't that bad and nothing appeared corroded). 

The trickiest bit was reassembly. The long pipe that came away with the lower section must engage with the tube that can be seen when looking up the main section towards the engine. Make sure that these two pipes mate up as it's very easy to miss with the long pipe resting alongside the tube rather than in it. Before the lower section may be pushed home, there are two pipes coming from the engine end that must mate up correctly with the lower section. To do this you need to remove the large neoprene cap you'll see in this lower section. Using a piece of stiffish wire bent into a hook at one end and a lot of patience each of these pipes can be seated in turn via the hole now exposed by the removal of this cap. Take care especially with the pipe that carries the cooling water to the engine as there is a neoprene seal that you don't want to damage. Once everything is seated correctly, do up the two bolts holding this unit on, press the neoprene cap back on and bolt the prop shaft housing back on to this lower unit. 

Having done all this I was now ready to add the lube oil. This time it was easy to pump the oil into the bottom hole until it came out of the top hole. Having sealed these holes with the bolts (top hole first before the pump is removed from the bottom hole), it was time to start the engine. 

The plastic dustbins issued by the British local authorities are ideal for this. They are deep and the plastic rim is strong enough and just the right size for bolting the o/b on to. Having bolted the o/b onto the bin (remembering to empty it first ) I then added water to the correct level, prepared the engine for cold start, said a quick prayer and pulled the cord. Bingo, away she went, sweet as a nut.


----------



## TSOJOURNER (Dec 16, 1999)

*Mercury 3.3 hp*

I have he manual for this engine and it says to put the engine a bit upside down and to fill up by the bottom screw as much as you can , after you close , you turn the engine upward and unscrew the upper one and let go the overflow until it stops because it is your adequate level of oil. Hopes it will help you.

regards

Frank:


----------



## The Pilot (Aug 25, 2017)

Lay your motor on a flat table with the oil fill and drain holes facing up; then use a 1 gallon paint can to elevate the prop end of the transom. This will make the drain and fill holes almost level. Fill until oil runs out of both holes. (use a syringe to make this MUCH easier). Then install the lower drain plug and stand the motor up right until oil stops weeping out of the fill hole. This will assure you have a full gear box, but that it's not over filled.


----------

