Help needed. Water in cylinder

[ragman]

Hi,
Just after any thoughts people may have. I have a yamaha 130hp saltwater series 2 stroke. It's a 2003 model with 150hrs. On the way back from my trip out last weekend it started running rough as when I got home and flushed it found it was only running on 3 cyl on low revs. Once it got up over 1500 rpm it would runfine on 4 cyls. Pulled out the plugs to check And one was milky. Thought it might have been a cracked head gasket so did a compression test and all cylinders were the same. If any one has any clues to help before I start pulling it apart that will be great

Craig

[myusernam]

what about water in the carbie?

[cormorant]

Water in a cylinder of a running motor usually cleans it and polishes it up removing all the carbon. Doesn't normally leave a milky emulsified oil - you're talking wet milky not dry white carbon?

Any chance of a photo?

If you are concerned it is water in there I would pull the plug and turn the motor over to get anything out of there and spray in some oil to coat teh bore until you resolve what is going on so it doesn't rust up.

[ragman]

Here's a pic. Not really clear but you can see it has a thick build up on it that was like a sludge. The other 3 plugs were perfect. It was the top right cylinder looking from the back of the boat forward. I have also sprayed some oil and kicked it over a few times on the weekend when it happened.
Thanks

[myusernam]

new plugs , suck it and see?

[captain rednut]

Cylinder head may have corroded a hole into the cylinder which i have seen several times, remove the head asap and lubricate the cylinder thoroughly to prevent bore damage.
cheers jimmy

[ragman]

So if that's the case compression would still be ok? I thought it would be down if there was a leak?

[FNQCairns]

Doesn't look like water to me...looks like a plug that was sitting in a cold cylinder while the hot engine was running.

I dunno but water seems unlikely. Clean up and/or replace and retry is what I would do first.

I would also run from a aux tank with known good fuel etc, and evacuate first all older fuel from the carbs and lines by flushing through with the new fuel while the bowl drain plugs are unscrewed.

[cormorant]

Looks like overoiling and fueling with poor or little spark.

Is the oil injection still connected or are you running premix?
Are you running the correct plugs
Check the plug lead and the plug connector and also the coil.
Does the motor still have thermostats in it?
Check carby linkages - is that carby butteryly opening? Float stuck ?
Not sure how that model motor " chokes" but check it is turning off on all carbys if manual and working properly is a electronic one.

[ragman]

thanks for the advice. decided to pull the head off today and found that the gasket had split. so lucky for me an easy fix.

[FNQCairns]

Glad you found a problem that could be easily fixed, split where to where? just curious.....there was no water in that cylinder as per plug pic...and you checked compression (although temp at the time can make a difference and so can too much unburnt oil residue).

Good result.

[cormorant]

No worries . Just trying to get you to look at all the non pull down options first. How bad was the corrosion and any scale in the galleries?

Glad you found it before any bore damage.

[captain rednut]

how could it have good compression with a split gasket??? just asking

[SunnyCoastMark]

how could it have good compression with a split gasket??? just asking

Possibly semi sealed by the sludge that is evident? -

150 hrs is a bit of a concern though - the 130 Yammies are a pretty good motor.

Any clues as to what might have caused the gasket to split? Has it ever run hot? i,e no water coming through?

[cormorant]

Possibly bad head gasket from manufacture, contamination on fitting , corrosion , bad surface, stretched head stud , warped head, warped block, very high water pressure, blocked water gallery, bad thread , crack in head or block, or simple as not tensioned ( over or under) down properly all create a weak point . Now replaced properly with all the above ruled out it will last a proper life time.


Sometimes they just fail and hope that is all it is. Luck of the draw but usually there is a reason but you don't always find it first time. Keep an eye on it after replacement.

Was there any discoloration or damage of bore or pitting on the piston?

Compression tests can be good with a fine gasket leak as the motor turns over so fast and may only show a small drop but a leakdown should pick it up. Have seen a lot of car ones where water leaks in and no gas goes into the waterjacket be it a porous gasket or the break in the gasket sort of acting like a flap valve. Harder to spot if all cylinders are low on compression to start with from overheat or wear so make sure you are right at the top of expected factory compression rating and are using the correct method and decent tester.