SX225TXRZ Water in #6

[randel1@comcast.net]

I have a customers boat that is getting water in #6 cyl. and fowling the plug. My first step was to pull and inspect the plugs. #6 was fowled with brown residue and the piston top had a layer of the same and was somewhat dry. A Compression test showed that cylinder to be within spec. Thinking it may be a blown head gasket I pulled the head and inspected it, the head gasket, and the cylinder and could find no apparent water entry point. I sent the head to the machine for inspection and milling should it be warped. It came back and I reassembled the motor with a new head gasket. I ran it up on hose connection for about an hour, no load and idle to 2500 rpm. Pulled the spark plug and it looked normal. My customer took the boat out for the weekend and returned it saying that it ran better but still did not have the hole shot or top end power it should have. I pulled the spark plug and again it was fowled showing water contamination in the cylinder. I have not had this problem with the Yamaha engines before but experienced it with OMC and it was caused by a leaking gasket in the exhaust system. Can a damaged gasket in the inner or outer exhaust plate on the Yamaha leak and cause water to get in a cylinder?

[99yam40]

Hope Rod or Boscoe drop in and respond with their experiance.

In the mean time, I would think the exhaust plates,gaskets, and divider would be a logical place to look

[randel1@comcast.net]

Water/exhaust plate removed

I pulled the exhaust/water passage cover to inspect for pin holes and or cracks in the casting between the water and exhaust passages. I found something rather odd that may or may not be a problem. There is a flat topped round nob a little smaller than a dime on the casting next to every cylinder. All of them but #6 are solid with no hole in them. But the one at #6 the cylinder getting water has a hole in it. I don't know if it is just coincidental and the hole is supposed to be there or if it has appeared due to corrosion or some other cause. See the attached pictures for more detail.

[rodbolt17]

I will have to wait.
I cannot open thumbnails.

[randel1@comcast.net]

Water in #6

Do I need to try to post the pictures in a different format in order to enable you to see them?

[99yam40]

here ya go

[oldmako69]

Sure looks like a smoking gun to me.

How much is a new casting? Or, a tube of JB weld and a SS nut and bolt?

[99yam40]

does not look like that came from corrosion

[oldmako69]

Call a Yam dealer and ask them if that thing is supposed to look like that. They ought to be able to tell you from the EPC.

[randel1@comcast.net]

Water in #6

Ever have one of those days when nothing ever goes right, well I didn't know they came in bunches like bananas. Apparently that hole is supposed to be there although I can't get anyone to confirm it. I have eliminated a crack or pin hole in the head and in the exhaust/water jacket area. The head has been surfaced and the cylinder sleeve is not cracked. I think that leaves the bottom side as the culprit. My first guess would be the lower crankshaft seal because I am seeing water in only the #6 hole. Any other suggestions before the power head comes off?

[TownsendsFJR1300]

Even thou its a two stroke, Do a leakdown test (piston at TDC) and see if it holds pressure. If there's a hole in the head, head gasket, ETC, you'll NOW know it as it'll leak. You may very well be able to hear it leaking(if there is a leak)..

[TownsendsFJR1300]

Where's rodbolt?

[rodbolt17]

I am here.
however it is a simple mechanical failure.
a leakdown test may help.
but mostly it is going to be eyeballs and that tool between the ears.

[TownsendsFJR1300]

Any updates???