'98 225 OX66 Oil Leak

[gw204]

I recently purchased a 25' Grady White Sailfish that is powered by twin '98 225 OX66 Yamahas. 371 hours on the original powerhead of stbd engine and about 25 hours on a new powerhead on the port engine. After lowering the port engine, oil began to leak from the bottom edge of the lower cowling and run down the leg. I removed the upper cowling and the only evidence of an oil leak I could find was on the bottom of the cover that goes over the throttle body. I looked around and didn't find any loose or disconnected hoses.<br /><br />Both engine passed an inspection by a certified Yamaha mechanic before I took delivery. <br /><br />Can any of you offer me some advice as to what the possible causes of this are? <br /><br />Thanks.

 

[rodbolt]

Re: '98 225 OX66 Oil Leak

either the oil transfer failed to shut off usually due to an improperly installed strainer or your engine oil tank cap is not sealing and its running out the top. if the oil is in the airbox its an overflow if its just all in the engine pan its most likly a leaking cap. you can try a wire tie around the cap to help it seal.

 

[gw204]

Re: '98 225 OX66 Oil Leak

Thanks rodbolt. <br /><br />When winterizing the engines yesterday, I noticed the oil in the bottom of the airbox. One thing I forgot to mention in my initial post is that the oil leaking out wasn't the same color as straight Yamalube. It was more the color of 4-stroke oil. Kinda brownish....which really has me wondering since the whole reason for the new powerhead was due to the motor taking some water through the exhaust during storm last fall/winter.<br /><br />I saw in another thread that you have been working on these things for quite some time. In your experience, is there usually a difference in sound between OEM and replacement Yamaha powerheads at idle? The engine with the original powerhead (now with 385 hours) is a bit quieter and cylinder compression is about 5 psi higher than the one with the newer (about 40 hours) powerhead. Do you think further break in will even things out? They both are running great and will crank up to 5500 without hesitation. <br /><br />Thanks.

 

[rodbolt]

Re: '98 225 OX66 Oil Leak

the PSI difference is no worries. its normal.<br /> the oil is most likly coming from a bad air box gasket, a air box drain hose that was left off or the strainer cap is leaking some when tilted.<br /> next time smell it though.<br /> if it smells like gas its posible the lower crank seal is dripping. without seeing it its difficult to tell. you will find that the air box tends to collect a lot of oil blown past the shutters and that is why there is a little gray hose from the lower port side of the air box to the block. its a drain to remove any puddled fuel mix from the airbox. remember the OX66 mixes fuel and oil at the vapor seperator not injected into the intake track like all other V precision blend motors. thats also why O2 sensor maint and periodic testing is absolutly critical. the ECU is so stupid it cant tell if the O2 sensor has failed it just reacts to the signal and can lean out the fuel mix above 4000 enough to smoke a piston.