Crank seal issue?

[Jjohnson1065]

Hey all,
My yamaha 1999 70 TLRX has never given me issues until the last time i had it on the water last fall. It ran very rough while on the water and refused to put out more power when trying to accelerate this day. When i got home, i trimmed the motor down and noticed fuel/ oil mixture draining out with the water around the prop (unburnt from exhaust?). This spring i brought it to a local yamaha dealer to have them check it out. According to them the compression is low (110, 105, 105 top to bottom) and the lower two cylinders have no vaccum and the motor is “tired”. All 3 cylinders have spark. They noted that it was possibly a crank seal issue and they couldnt get parts which is BS because i had the entire powerhead gasket repair kit delivered within a week. Fast forward to now. I have removed and cleaned the carbs- they looked good, have changed the head gaskets and inspected the top crank seal which also looked good. I have also tuned the carbs according to the factory repair manual. The motor idles nice at 850rpm when its in the water but rough when on muffs in the driveway. After being out on the water i am still getting the gas/ oil mixture draining around the prop. Also noticed it runs rougher when the throttles about half way 3500-4000rpm range but smoothes out when closer to wide open. Anyone else experience this? Does it sound like the lower crank seal is the issue? Let me know what you guys think.
Thank you,
Jared

 

[99yam40]

I would make sure the spark timing is in spec and that it advances in spec also, by using a timing light.
If a cylinder is not burning the fuel properly there will be some fuel/oil mix going out thru the exhaust.
very hard to make sure spark is happening on all plugs when there is loss of power at different RPM, but you might be able to see it with a timing light with the cowling off so you can move the light to the different plug wires

 

[Mc Tool]

Google sez compression should be 110 to 130 psi so it aint terrible.
Its possible that it sounds rough on the muffs coz its noisier and its actually the same in the water but quieter .
I would verify running float level ......put a piece of clear tube on the carb drain nipple and hold tube pointing up ( hold it up with sticky tape or rubber band ) start the motor and open drain screw ....you will see the fuel level in the tube. It should be below the fuel bowl gasket by a few mm , thing to do is make sure they are all the same .
While its running rough pull one plug lead off at a time to see if you can suss which pot is not firing .
Oh , and yeah ....find yourself another boat shop to take it to , Im sure the BS is not limited to "couldnt get the parts ".
Have you given it a new set of plugs ?