Mercury 2.5hp 2 stroke oil leak

[Saltram31]

After using the engine today there was oil leaking from the leg which must mean gearbox issues.The motor came with our recently purchased yacht so I'm not familiar with 2 strokes. What should I check and replace as I would like to keep the motor as it runs pretty well.
TIA

 

[VicS]

After using the engine today there was oil leaking from the leg which must mean gearbox issues.The motor came with our recently purchased yacht so I'm not familiar with 2 strokes. What should I check and replace as I would like to keep the motor as it runs pretty well.
TIA

Most likely just unburnt oil from the 2 stroke fuel mix. It its black, smells burnt or of petrol that's what it is. and perfectly normal.

If its a thick oil that smells like EP gear oil then it is gear oil and the gearbox will need some new seals ......... but before tearing into that check the gear oil for signs of water ingress ...... You'll be changing the oil anyway won't you if you have not already done so.

See http://forums.iboats.com/forum/engi...2616-oil-leaking-around-lower-unit-by-iwombat

 

[Saltram31]

Appreciate the helpful reply and link, Vic. Thanks.

 

[neil_s]

I have one. It also came second hand with a boat I bought. It occasionally needs a piece of wire poked up the piddle pipe to keep it clear. I do make a point of flushing it through with fresh water after use, and I run it on 50:1 fuel mixture.

 

[Channel Sailor]

If one of the Tohatsu base engines then these little outboards are excellent, usually so little to go wrong. If you are running it on between 50 and 100 to 1 oil mix then there should not be oil residual too apparent, if at all. I run mine on 70 to 1. On 50 to 1 I found it did not start so easily. I measure the oil for the mix very accurately with a small measuring cup, no guess work using the graduations on the side of the oil bottle.

Also check both the gearbox oil fill and drain fibre washers are not leaking. I replace my washers every two years.
If the leaking oil is milky and slippery then it would be from the gear box. If black and sooty then it would be 2st residue.

You could drop the lower leg off to see if the exhaust/drive shaft tube is soaked in gritty/sooty black oil and a lot of carbon deposits. If yes then it must be too much oil in the fuel mix. There us a knack to putting it back together but you get used to it after doing it a few times. This should be done every year anyway.

 

[CLB]

Can you post a picture of where the oil is leaking from. This wil then make it easy for those in the know to diagnose whether it is gearbox oil or I burnt fuel oil. I have a 3.3 HP version of the engine and it always leaks a little unburbt fuel oil from low down on the leg after use.

 

[Saltram31]

I have one. It also came second hand with a boat I bought. It occasionally needs a piece of wire poked up the piddle pipe to keep it clear. I do make a point of flushing it through with fresh water after use, and I run it on 50:1 fuel mixture.

I mixed it 50:1 which was recommended by the previous owner. What method do you use to flush the motor as it does not have neutral so I doubt starting it in a bucket would have the desired effect due to the prop wash. I see that we are neighbours. My yacht is in the Nutbourne channel.

 

[Saltram31]

Thanks CS. I was thinking of stripping it down to give it a service and to learn the ins and outs. The oil residue is not milky so hopefully not from the gearbox but there was a fair amount which had me a bit puzzled.

 

[VicS]

I mixed it 50:1 which was recommended by the previous owner. What method do you use to flush the motor as it does not have neutral so I doubt starting it in a bucket would have the desired effect due to the prop wash.

ITYWF that 50:1 is also the mix stipulated in the owner's manual.

You can take the prop off to run it in a bucket but make sure your bucket is deep enough to immerse the water pump. Remove the split pin and once the prop is off retrieve the drive pin and put both somewhere safe!

The unburnt oil residue from the fuel will be worse after light running or flushing than it will be immediately after a hard run.

If you have mistalid your owners manual you can down load one from Brunswick Marine's "Download center" at http://download.brunswick-marine.com/download/preparesearch;jsessionid=1908i1dm8ap4y?lang=EN&mod=4.
It is not always easy to find the right manual , in fact often better not to specify a year, just select "outboards" and browse "all" until you find the right one.

 

[VicS]

If you have mistalid your owners manual you can down load one from Brunswick Marine's "Download center"

and you will find the Service manual at http://boatinfo.no/lib/mercury/manuals/22-25-3-33.html

 

[jwilson]

After using the engine today there was oil leaking from the leg which must mean gearbox issues.The motor came with our recently purchased yacht so I'm not familiar with 2 strokes. What should I check and replace as I would like to keep the motor as it runs pretty well.
TIA

I have twice had charterers say my Tohatsu tender engine was leaking oil: a few drips down onto the transom from it's pushpit rail mount after use. Never actually been an oil leak, just lengthy low-rev running which creates a slightly oily exhaust. It doesn't drip oil after use if used with plenty of throttle. Mine runs on 50:1.

Or it could be the gearbox oil seal...... but on mine now 10 years old it's still original and doesn't leak.