found my yamaha 2.6 noise....

[mackeral5]

crank is TOAST. glad I tore it down before it scattered. surprisingly it already had the 6g500 exhaust plate, considering it was originally a 175 with the 4 port reeds and tiny carbs. it had been built before, all 6 holes are .50mm oversized. I'm considering matching the ports to a blown 220sp block I have.

http://www.myfishingpictures.com/data/500/medium/etc_232.jpg

http://www.myfishingpictures.com/data/500/medium/etc_233.jpg

[mcyama]

Man that doesn't look for the back pocket. What broke? Hope Santa brings you a new powerhead. By the way did you kill the grimlins that caused this? Martin

[mackeral5]

this powerhead always had a noise in it since the day I installed it. I was in a bind when I blew my v4 and we had this old 175 hanging in the shop, nobody knew anything about it. it had decent compression and spark, so I swapped it onto my v4 mid (after a tuner swap of course). I ran it for over 200 hours before finally pulling it apart today. how it lived so long I dunno. it was ran at 6200rpm for much of the time I ran it, lol....

any recommendations on what to look for that would have caused a top bearing failure? fortunately I have another crank but I don't want to screw it up....

[Charger200]

It could have been run a lil dry, subsequently got hot and had a couple rollers fail

[mcyama]

mike I have seen it so many times. I don't believe that it was a pre existing problem. ASyou can tell water has washed the lube away. Unless you tell me otherwise I believe that the unit was built back with an aftermarket gasket kit, of inferior quality. Also yamaha played around with some terrible gasket material in the mid 90's. Does the gaskets look rotten or they made with a red color material if so there is your problem. thanks Martin

[mackeral5]

martin, the gaskets appear to be oem yamaha, they were "stuck" in place pretty good and had the metal liner/reinforcement in the gasket material. there is a decent amount of rust on the top of the crank as well as right outside of the areas where the rod bearings run on the crank. thinking back I swapped flywheels because the magnets, were real rusty on the original flywheel. maybe this motor went under at some point in time?

when I got the powerhead it did use the oil pump, but I converted to premix, and always mixed between 32-40:1.

[mcyama]

Mike did you ck the top crank seal to see if it is still soft? make sure that the spring was still in it. Water is entering powerhead from somewhere. thanks Martin

[mackeral5]

the top seal is kinda hard. another thing, it was a little dark when I tore the powerhead down. now that I put a little light on it, there's rust all over the crank, top to bottom. no rust on the rods though. i'd almost swear this thing went under at some point in its life...

it will be a low budget re-assembly. new gaskets, rings, seals, orings. I've got a ton of "good" used bearings salvaged from other powerheads, unfortunately my current budget isn't going to allow new bearings......I've got to get my work/fishing boat back on the water, even if that means taking a little risk until spring when business picks up.

[VectorPat]

Its probably the lower seal, it can leak water in on boats that sit low in the rear or if water sprays into the area when planning or coming off of plane. The recirc system will force the water to the upper bearing then flow down from there.