50 2 stoke upper main bearing...

[maintainerman69]

I have a 2003 50tlrb. Last spring the upper main baring failed. It stared to wine and the seized. I broke the motor down and took it to the local machine shop/ powerhead rebuilder. He said I most likely had condensation in the oil tank with lead to water on the bearing. He pressed on a new bearing and all was fine, until this weekend I was fishing the Delaware bay and on the way in heard the same bearing wine...When I got home I ran the motor in the driveway and it is definitely the upper main crank bearing again!! Anyone have an idea what could case this to go bad again??? I checked for water in the oil tank...clean. I ran the boat for about 70 hours this spring with no problems and 375 hours since I replaced the bearing last spring.

[rodbolt17]

carefully check all the recirc nipples/checkvalves.
did you replace the rest of the crank bearings or just the upper?

most water issues in the oil tank are NOT condensation but water leaking past the plastic fill port on the hood and collecting in the spill catch and draining past the fill plug.

my recommendation is removing the spill catcher and sealing the hood fill port.
Carolina machine(formerly Ackermann marine) can rebuild that built up style crank.

IF the other bearings were not replaced then its possible debris from another bearing caused another failure.

[kokevako]

Blowing air travels in only one direction.
Part number 3 and 7.

2003 50TLRB Yamaha Outboard CYLINDER CRANKCASE Diagram and Parts

Jari

[maintainerman69]

I replaced just the upper bearing as we could easily see it was bad..the lower and mid bearing looked fine and didnt see like was worth breaking the whole crank bown to replace them. I did check all the valves while I had the block broken down and blew air threw each fitting int the appropriate direction. I did order new checks along with the new bearing and seas/ gaskets needed to do the job. We are thinking the bearing (aftermarket) was just poorly made?

Or could it be a lean carb issue? I do need to read up more on the yammi precision blend system...

[maintainerman69]

so I had the new bearing presssed on and am about to resemble the powerhead. my question is how do I replace the reserc nipples? can I just pull them out with a vise grip type puller? then tap new ones in lightly with a hammer? any sealant needed? THANKS...

[rodbolt17]

yep.
I typically wipe a smear of loc tite 518.