99 Yama 150 V6 Rattle

BBell

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Apr 8, 2010
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Ok i will start at day 1 so i dont leave anything out.

My dad bought this 1999 19' Sailfish with a 150 Yamaha v6 2 Stroke awhile back maybe in 2002 or so. He didnt use it very much it sat more than anything, it was to small to go out in the atlantic most of the time. His wife passed a few years later and it again sat for a few more years until he tried to sell it. He found no buyers for what he wanted for it so he pretty much gave it to me and my brother. We took it out a few times with no problems at all then he took it out with a friend in the bay and it developed a rattle in the top end of the engine. It only rattles when its above idle, it has plenty of power so i have ruled out a piston or rod. My guess would be a crank shaft bearing or something in the stator causing the rattle i have not sat there and listened to it because if it is a major internal problem i dont want to cause anymore problems. it was shut off as soon as it started rattling i have confirmed he did put the right amount of oil in it it ran fine for about an hour then it started showing its *** he did change the brand of oil he put in it but it was approved for yamaha engines.

I just would like a list of things to look for so when i start to tear into it i know where to look and dont overlook anything. We are mechanically inclined so we can figure it out im sure.
 

robert graham

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Apr 16, 2009
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Re: 99 Yama 150 V6 Rattle

Maybe run the motor with shroud removed, 2 guys in boat, a driver and a "find the rattle" guy. I had a rattle and it was the black plastic throttle control slide vibrating, easy fix, but it was making a racket. Also these motors make lots of whirring, clicking, rattling noises. I heard a noise once and asked my wife about it and she said the sound was "mostly in your paranoid head", and she was right, and that was several years ago. You could have a bit of piston slap which may be normal. Good Luck!
 

BBell

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Apr 8, 2010
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Re: 99 Yama 150 V6 Rattle

i know it is not a normal rattle or cling; its a bang.
 

robert graham

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Re: 99 Yama 150 V6 Rattle

Well, you're smart to dig in and find it before it self-destructs. Good Luck!
 

robert graham

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Re: 99 Yama 150 V6 Rattle

Seems I remember a while back, our resident "real expert", Rodbolt mentioned an engine balancer device mounted on the crankshaft of some of these motors that would rattle and vibrate a lot before they came apart in a big way. What you describe sounds similar to that. Maybe we can do a search on "balancers"?
 

BBell

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Apr 8, 2010
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Re: 99 Yama 150 V6 Rattle

yeah i wasnt sure if this motor had the harmonic balancer on the crankshaft or not. thats always a possiblility
 

robert graham

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Apr 16, 2009
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6,908
Re: 99 Yama 150 V6 Rattle

If you can address a thread directly to Rodbolt regarding this possible balancer issue, he'll probably come back to you with some very useful information, might save you a lot of time and money on the repair. I doubt the balancer replacement is cheap, but a lot better than a new power head, and sounds like the rest of your motor is good. Hope this helps!
 

99yam40

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Sep 7, 2008
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9,116
Re: 99 Yama 150 V6 Rattle

Just like all motors that you start to work on, start with the basics pull the plugs and inspect, check compression. This will tell you if something is gone wrong with a piston most of the time.

I have had one guy say he thought there was something wrong with his lower unit because of the noise. Turned out to have pieces of a piston that were too large to go all the way out rattling around in the prop exhaust hub. It was running on only 5.

Something that sat up as much as that one ,I would have looked into cleaning the fuel systems before running, just to be sure.
Hope you do not find anything major.
 
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