F40 BETL year 2000

[ianlakeside]

Hi this is my first post. I have 2 F40BETL engines 12 years old both with the same problem. The symptoms are that afer short running hours (approx 40) after an oil and filter chage the oil becomes contaminated. It looks like it could be water because the color turns a creamy colour and the viscosity seems to thicken.

The engines both start and run very well and are generaly in good condition. I took the engines to a Yamaha service centre for investigation but the problem still persists. The dealer suspected fuel contamination, and the problems assocated with new fuels were investigated. This has not resolved the probem, I asked if the head gaskets could be blown but that was discounted as the engine starts, runs well and does not overheat.

I was talking to another boating enhusiast and he advised me that it may be a problem wth the exhaust system that runs through the oil sump allowing water in the sump.
I'm at a loss and would appreciate any help to resolve this problem.

regards

[boats.net]

Smell the oil to see if smells like gas. Could be leaking head gasket or oil pan gasket.

[arny]

Most probarly stuck open thermostat-take a look on it first before doing anything else.

[ianlakeside]

Hi Arny,
Thanks for your post, I hadnt considered that the thermostat could cause problems but will check it out.

regards

[ianlakeside]

Thanks for your post. I have done the smell test and the oil just smells like oil. I have been in discussion with the Yamaha service centre again to try and workout what checks could be made to determine where the problem was before actually dismantaling the engine(s). I dont have a diagram of the engine so its difficult to workout areas to check. Its a concern that both engines show the same problem.

regards

[damirdaco]

if the engine does not overheated, probably the problem is oil pan gasket.