1994 Yamaha 75hp Compressions - Help!

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thesubdragon

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Oct 19, 2005
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I am looking to purchase a 1994, 17 foot key west with a 94 75hp Yamaha. I had a mobile marine mechanic go out and check out the motor. Compression check, lower unit, carbs, ect. The compressions came back as 90lbs on #1 cylinder, 85lbs on #2, and 90lbs on #3. I am concerned because I thought the compressions should be in the 100-120lbs range. Can anyone help me out and let me know if this is a sign of bad things to come. I can purchase the boat for $4800.
 
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rodbolt

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Re: 1994 Yamaha 75hp Compressions - Help!

sounds about right.<br /> have the boat taken someplace that can do a leak down test. a leakdown will tell if the cyl sealing is acceptable or not.
 
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thesubdragon

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Re: 1994 Yamaha 75hp Compressions - Help!

Thanks for the info. I just spoke to a tech and he informs me that there really aren't compressions specifications. What he goes by is the difference in the compression between the cylinders. A 10 to 15 psi difference between cylinders he would consider a bad sign. He feels I should not be alarmed with the compression of 90, 85 , 90. Anybody with any thoughts, please help.
 
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thesubdragon

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Re: 1994 Yamaha 75hp Compressions - Help!

I am very interested in this boat, but at the same time, I don't want to purchase something that in a year I am going to need to rebuild the heads. Comments please!!
 
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rodbolt

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Re: 1994 Yamaha 75hp Compressions - Help!

you will find if the compression is good now it will be good years from now. 2 strokes really dont wear much usually someone neglects the maint and they die in minutes. but if you have any concerns have a leakdown test done. its 10 times more accurate than a compression test. anything over 10% leakage and ill turn it away.<br />one the rings on a 2 stroke leak combustion gasses they usually die 1/2 hour later or so.
 
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phatmanmike

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Oct 24, 2003
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Re: 1994 Yamaha 75hp Compressions - Help!

I don't want to purchase something that in a year I am going to need to rebuild the heads
Click to expand...
dude, you dont rebuild a 2 stroke head.<br /><br />the motors compression sounds just fine. yammy makes a great motor. have fun
 
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