Hello, My brother purchased a used boat with a Yamaha 50 hp 2 stroke engine, mix type. (not oil injected). Sorry, don't have model number right now. Upon removing the engine cover I noticed where some oil had sprayed or slung out from the flywheel and got on the inside of the cover as well as generally coated the engine itself with some even on the pulse or pickup coil. Does this indicate a leaky crank seal? Do these seals normally leak or pop out? Is it replaceable without splitting the engine cases? Also is there another source of oil.? Any help or advice would be appreciated. Thanks, Robert
hello if it runs ok I would not sweat it. if it does not cough or stall at an idle then no worries. how old is the motor? are you sure it came from the flywheel and was not drawn to it? are you sure its not something like fluid film that was sprayed on? but mostly 2 strokes dont stay clean and shiney for their entire lives. clean it of and keep watching it. but no there is no removal and installation tools for replacing the seal with it still in the block. its rare to see that type of failure. good luck and keep posting.
If, in fact you are losing fuel/oil mixture from the top seal, you are losing crankcase pressure which will cause the engine to run lean. You also are losing lubrication to the top bearing. You do not have to split the case to change the seal. First thing, get a service manual for that engine. You will need a proper flywheel remover and slide hammer type seal remover (the type with a self-tapping screw in the end. Remove the flywheel, stator & trigger assembly. Then carefully drill 2 holes in the seal. Screw the slide hammer into each hole alternately and pull seal out. Using a large socket or similar item, tap the new seal in.
Thanks for the encouraging response. I hope it is something minor like you said. Unfortunately we didn't get to really test the engine so we will find out about the running qualities soon. By the way, the starter was real loose?? Makes ya wonder?? Maybe it just loosened from vibration but I also suspected it was "left" loose by a mechanic but who knows? No evidence that it has been wrenched on otherwise. I tightened the starter bolts up. Oh well, everything looks great otherwise and I'm hoping it runs good. Enough speculation, will test it and we will let you know how it goes. Thanks again, Robert
lakensea , Thank you as well. Sounds like the seal is almost identical to the Yamaha motorcycle crank seals I replaced many moons ago. I will clean the engine off and run it some and recheck for oil. I am aware that if it is lean because of a seal it could hole a piston so I will be very cautious on test runs. I may just pull the flywheel anyway to be sure. Gotta come up with a puller first. Thanks again, Robert
Before I could take a look at the engine again the boat was taken to a shop. They ran the engine and said it was ok and totally disregarded my blown crank seal theory. This morning I went along with my brother to the lake where we ran it and it did fairly well but idled a little rougher than I thought it should. I went home and my brother fished for several hours and then returned home. He checked the engine cover and new fresh oil had slung onto the engine cover and all parts around the flywheel were oil coated. That was more than I could stand so we bought a puller and removed the flywheel. Sure enough the crank seal was bad. The outer body of the crank seal was there but the entire seal lip center part was gone. I'm just glad it didn't burn a hole in a piston on our test drive. I plan to get the seal and replace it.
Yamaha 50 hp, oil slung off flywheel ??
if it runs ok I would not sweat it. if it does not cough or stall at an idle then no worries. how old is the motor? are you sure it came from the flywheel and was not drawn to it?
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