Mercury 1999 9.9 hp

[OFF SIDE]

I recently purchased a mercury 9.9 hp to take my grandchildren fishing. It was reassured by the previous owner the motor was in good working order.
The second time taking the kids out the motor seemed to work fine, however when I went to use it the next day I couldn't pull the cord out to start. The spark plugs were removed and water was observed on the plugs.
I sprayed some oil into each cylinder and worked the flywheel, the pistons freed up .
The motor was put on a stand with water and ran again, the same results occurred, drops of water on both plugs.
I'm mechanically inclined, not alot of work on boat motors other than basic maintenance.
Does this motor need a head gasket or ?
Any help would be greatly appreciated.

 

[racerone]

A 2 stroke or 4 stroke ?-----I do not believe it has a head gasket if it is a 2 stroke.----Seriaal # is ?

 

[OFF SIDE]

Hi tks for your reply. The motor is a 2 stroke . See attached photo.

 

[racerone]

No head gasket on those that can leak water into the cylinders

 

[OFF SIDE]

Tks! Any ideas on what the problem could be? I took the spark plugs out , put penetrating oil in each cylinder. Removed the recoil,worked the flywheel everything is moving again.

 

[racerone]

Well---You have to sort this out yesterday.-----Water inside an outboard will quickly destroy the bearings

 

[QBhoy]

Hi. If it’s just a little sign of moisture on the plugs…how sure are you that you don’t have water in your fuel ? Or if it has a small in line filter…some in there.
The alternative (if indeed it’s not likely to be the head)…isn’t good…would mean that you have serious corrosion to the extent that it’s rotted through the water jacket and into both cylinders. Probably unlikely and rare though. I’d imagine you’d be able to tell by its external condition, if it’s been exposed to extreme conditions, that’s allowed this.
I’d be odds on for water in your fuel perhaps.

 

[OFF SIDE]

Hi. If it’s just a little sign of moisture on the plugs…how sure are you that you don’t have water in your fuel ? Or if it has a small in line filter…some in there.
The alternative (if indeed it’s not likely to be the head)…isn’t good…would mean that you have serious corrosion to the extent that it’s rotted through the water jacket and into both cylinders. Probably unlikely and rare though. I’d imagine you’d be able to tell by its external condition, if it’s been exposed to extreme conditions, that’s allowed this.
I’d be odds on for water in your fuel perhaps.

Tks. I drained the fuel from the tank into a clear jug, doesn't seem to have water in the fuel, constant blue colour, 50:1 mix.
I have attached a photo of the plugs. The motor has been run in fresh water, no corrosion that can be seen. The motor runs and idles as it should.

 

[QBhoy]

Tks. I drained the fuel from the tank into a clear jug, doesn't seem to have water in the fuel, constant blue colour, 50:1 mix.
I have attached a photo of the plugs. The motor has been run in fresh water, no corrosion that can be seen. The motor runs and idles as it should.

Ok. Think you should do a compression test on her then.
So you pretty sure that the reason you couldn’t pull it easily, was because it was locked up with water ? Did water come out the plug holes when you pulled it over too ?(with plugs out)
Any chance it was in gear when you pulled it and wouldn’t pull ? If it was locked up with water…I think you’d know all about it with water pumping out the plug holes when pulling her over with plugs out.
Only other thing I can think of is that water somehow got in there by some freak event during transport, storage or washing it down ? Just given that it ran the time before. No way that water got into carb somehow or into the fuel line and primer bulb ?

 

[QBhoy]

Just thinking on it. That engine might be new enough to have a interlocking device that won’t let you pull it, when in gear.
Possible that happened?

 

[OFF SIDE]

Just thinking on it. That engine might be new enough to have a interlocking device that won’t let you pull it, when in gear.
Possible that happened?

There is no water coming out the plug holes, just water on the plugs. When I ran it it would pull over after every time, next day in neutral the pull cord wouldn't move. I'm not leaning on water on the fuel, seems to be all good.
I'll do a compression test on the cylinders.

 

[racerone]

Mercury used interlock set-up in the 1970's !!

 

[QBhoy]

Mercury used interlock set-up in the 1970's !!

Fair play. Suppose I was more referring to the smaller engines though. Haha. I’m sure you were already aware I was perhaps.

 

[QBhoy]

There is no water coming out the plug holes, just water on the plugs. When I ran it it would pull over after every time, next day in neutral the pull cord wouldn't move. I'm not leaning on water on the fuel, seems to be all good.
I'll do a compression test on the cylinders.

You never mentioned about the idea of maybe it being in gear. Check to see if you have that lock out on your engine. I’d say.

 

[racerone]

Shift interlock was used on the 7.5 and 9.8 HP models in the 1970's

 

[QBhoy]

Shift interlock was used on the 7.5 and 9.8 HP models in the 1970's

Ah. Didn’t know that. Excellent info. Never owned either of them. Had most others from merc and Yamaha 10hp and below. Only one close was a 4.5 merc. Briefly had a white hood merc 10hp (100 or 110) maybe. Never ran. Never used.

 

[OFF SIDE]

I performed a compression test on both cylinders, both came out as 110 psi. This reading is more than acceptable. Next step is new gas oil, don't know what else can be done.

 

[OFF SIDE]

Found the problem! Removed the casing to expose the pistons, the previous owner had reversed the two gaskets, water was entering the cylinders as result of the different gaskets. Also it looks like the plate was not torqued in a pattern recommended.
Searching now for the torque pattern/values and part number for replacement gaskets.
Thanks for all you're input guys.

 

[flyingscott]

Did you leave the motor in gear when you shut it off? There is a recoil lock on that if you leave the throttle advanced. That motor has the shifter in the tiller handle?

 

[airshot]

Now you understand that some folks will say anything to make a sale.....always thoroughly check and test before buying. Glad you found the issue, doesnt look like it will be costly, just some labor......good luck....