Originally Posted by john20
Robbie yes the oil has risen on the dipstick since the problem has been occuring. would this symbolise fuel in oil? Again thanks for your help..
Some Yam outboards are prone to "making oil" when run at low rpm for extended periods (think trolling for salmon.) In those cases it's generally assumed an excess of cooling water and a lack of heat generation from the powerhead casing a lot of unburned fuel to remain in the system.
IIRC, symptoms are a cloudy/milky oil appearance, and a definite fuel smell to the oil (not sure if this would show up on a diesel.) It affects lubricity to some degree, so should be addressed, but the solution can be hard to pin down (I've heard differing routes including running warmer thermostats, ring replacement, or just opening up the throttle now and then.)
A web search for "making oil" should get you more info.