Identifying faulty seal water in oil, Outboard Yamaha 6

[dial_amonkey]

I just discovered water mixed in the oil of our 5 year old Yamaha 6 outboard: Coffee colored oil

I presume a seal, gasket or oring has gone bad, the engine had not overheated, starts first pull, normal power.

Does anyone have any troubleshooting tips that could help identify the faulty seal?

I'm currently in Fiji so getting parts in can be difficult

I wondered if I could pressurize the crankcase with air and the crankcase breather hose and look for oil leaking or listen for air escaping - would this work? I would need the leg in a bucket i guess.

I also would try this using the spark plug port to check the head gasket -

I would very much appreciate other tips, hints, advice or ideas,we use the outboard everyday ..

Searching the forums I found this from 'tkeithlu' "any gasket that lies between the coolant passages and the valves/cylinder/crankcase, not just the head gasket. The other is a crack in a similar location" This leaves a lot of possibilities.


Many thanks for any ideas.

[mlydon]

Most likely a head gasket. Check your compression first. You can also remove the thermostat, pressurize the cylinder(s) with air, and see if you have a breeze coming from the thermostat housing. There aren’t really any penetrations of the water jacket to worry about - the jackets are designed to run around valves, spark plugs, etc.

Matt