2000 Yamaha 9.9 2 stroke won't start

Sea Rider

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Sep 20, 2008
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12,345
Hey calm down, relax, the parts diagram for said motor : https://www.boats.net/catalog/yamaha/outboard-by-year/2000/9-9mshy/crankshaft-piston, doesn't show that labyirinth seal being available as a spare part, comes included if buying the whole crankshaft, perfectly know what they are for, Tohatsu uses them but are plain round and wide, complete different shape from the Yam's, that's why my misinterpretation so have schooled me nothing...
To end this nonsense conversation with both, compare the 9-3 pic of said current crankshaft's brownish color to this one.
Yam 9.9 Crankshaft Assy.jpg


are both similar in color ? Really ? Without precise information will never know what went wrong with said motor as it's unknown if used in fresh or salted water, if the the combo capsized and was recovered or if the motor went diving and stored after that nasty episode.

Gee Fast, how darn horrible you get when upset!! I'm out, Hasta la Vista Babies....

Happy Boating
 

SeaRogue

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Oct 12, 2021
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Well. This got interesting. So, I understand that there's wear and tear showing on the crank shaft, this doesn't sound to me as indicative of failure, but of an older motor, which should be to expected. The 'labyrinth seal', part # provided by fazt no longer seals, and somehow failed, the question I have, is would this seal failing cause a no start condition. My guess, and only a guess, is that the top cylinder would be pulling air from the bottom cylinder, and vice versa, with the result that the carb wouldn't function, as it doesn't have adequate air movement. Keep in mind that the cylinders were showing 130 psi compression when I bought the engine.

On that note, I am assuming it's an involved job to replace that seal? Further edit, reread FB's mention to take it to a rebuilder.

FYI, I took the the crankshaft to a Yamaha dealer, and was given a quote for parts to replace on the crankshaft, which was basically everything, for $500 CA, plus labor, tax, etc. All well and good, but doesn't tell me why this motor won't run. I'm going to try find some local old timer/backyard mechanics for more opinions, and will go from there. Edit to this part, I double checked the list the Yamaha dealer gave me, and the parts have to do with replacing the piston heads. Nothing at all to do with the crankshaft.
 
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99yam40

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Sep 7, 2008
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8,871
yes top , or bottom crank seal can keep one of the cylinders or the middle seal will keep both cylinders from drawing air and fuel thru the carb into the crankcase and into the cylinder.
as I posted before you can send the crank off to be rebuilt with new seals and bearing.
my C40 cost me about $400 a couple of years ago and it is a 3 cylinder

you just need to find the machine shop that does this all the time, they can get the parts needed

a 2 stroke motor can get enough air in to the cylinder from the exhaust so you do not even need to open the throttle to get a good compression reading.
4 stroke motor is totally different on that
 
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Faztbullet

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Call the company below...
See if they will let you supply parts such as bearings and seal. SeaRider you CANNOT compare an new or reman cranks surfaces to a used one.
 
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Sea Rider

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Sea Rogue, if you're located in the USA, why would you need to send that crankshaft Canada to have it rebuilt there. If all the required parts that's needed to work right as from out of the box are not available specially the labyrinth seal and the crank-pin that holds the middle ball bearing side to the labyrinth, better get a complete used 9.9 crankshaft with connecting rods, piston and rings will be a lot cheaper and faster. Install new upper and lower oil seals and any other minor part that's required and will be back to boating soon...

A s a plain curiosity of mine, sent those rusted/overheated whatever happened crankshaft's pics to the local Yam Service to have a tech opinion and the answer was : that motor went diving or has suffered a slow overheat due to poor lubrication by previous owner...

Yam 9.9 Labyrinth Seal.JPG

A a comparison sent me this pic which say it all, it's from a 2000/2 stroke Yam 9.9 motor which came in for a 300 hour internal preventive maintenance, all the internal parts seen inside the crankcase highly differs nor has anything to do with the current shot crankshaft's color nor state. So Fazt's CANNOT compare an New or Reman cranks surfaces to a Used One doesn't apply at al...

Happy Boating
 

Faztbullet

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Dang you just hate to be proven wrong Searider. You can see the crankcase flanges have been cleaned and most likely the crank also as it being reassembled in pic not disassembled...wrong again. And from pic and parts laying on bench it could be a replacement crank. In the 40+ years and several hundreds of engines I have repaired not counting the several hundred rebuilt seen this quite often. Sorry you have never seen this in the 4 or 5 you have dinked with..
 

Sea Rider

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Hey FB what have you been smoking lately that makes you think you always have the correct response to my posts? My posted pic was just a visual comparison between both crakshafts and how they should look if the motor is well cared for. The issue with negacionist boaters is that usually fly high over the Cuckoo's nest as it's the case.

To nip your high tech speculation intent, the complety story is as follows : the motor belongs to a boating mate, was sent to the Yam dealer because was impossible to rope crank, a Pandemia moment, was found that the lower crankshaft's oil seal cone was found extremely salt seized, for your knowledge, motors having such lower oil seals tends doing so when their lower leg sits submerge in salt water for too darn long time period. If such oil seal is not well greased periodically with a ton of marine grease it's the worst case escenario.

Dealer cleaned nothing the crankcase was split open just for inspection and closed back again, the lower oil seal was well greased and reinstalled back along a new base gasket and voila !!! don't surprise adding malicious mystery to your post to attest better your amazing unverified and unreal posted scenario. For my mental health I no longer pay the slightest attention to the mean comments coming from you. Can keep tearing and repairing Jurrassic motors for the next 40 years...

Happy Boating


 

99yam40

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Sep 7, 2008
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Hey FB what have you been smoking lately that makes you think you always have the correct response to my posts? My posted pic was just a visual comparison between both crakshafts and how they should look if the motor is well cared for. The issue with negacionist boaters is that usually fly high over the Cuckoo's nest as it's the case.

To nip your high tech speculation intent, the complety story is as follows : the motor belongs to a boating mate, was sent to the Yam dealer because was impossible to rope crank, a Pandemia moment, was found that the lower crankshaft's oil seal cone was found extremely salt seized, for your knowledge, motors having such lower oil seals tends doing so when their lower leg sits submerge in salt water for too darn long time period. If such oil seal is not well greased periodically with a ton of marine grease it's the worst case escenario.

Dealer cleaned nothing the crankcase was split open just for inspection and closed back again, the lower oil seal was well greased and reinstalled back along a new base gasket and voila !!! don't surprise adding malicious mystery to your post to attest better your amazing unverified and unreal posted scenario. For my mental health I no longer pay the slightest attention to the mean comments coming from you. Can keep tearing and repairing Jurrassic motors for the next 40 years...

Happy Boating


and I though you were gone from this thread from what you wrote before, I guess you just cannot leave even when you say you are gone​
 

Faztbullet

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Mar 2, 2008
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15,616
Dealer cleaned nothing the crankcase was split open just for inspection and closed back again, the lower oil seal was well greased and reinstalled back along a new base gasket and voila !!!
You post so much misinformation I doubt the above is correct and only has half truth to it. If true it also shows the techie at dealer and yourself are ignorant in engine repair as crankcase flanges have to have sealer.
 
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