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Pre 80s merc 90 hp doesn't pee at idle

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ryans01z28

Contributing Member
I can't remember what yr this motor is maybe a 78-79 not sure. My motor doesn't pee when it idles but if I speed it up it will start to pee. I blew compressed air into the hole to make sure nothing was obstructing. Is the impeller going out. I was thinking I sucked up sand in it but I just put this motor on and ran it one time in the water. It didn't pee at idle when I had it on the hose for the 1st time either.
 
I do not believe those have an overheat buzzer.-------So you must install a new impeller every 3 years !!!.--------Vanes have likely taken a " set " resulting in low presssure at idle.
 
Is that very hard. I'm a mechanic so to speak but never really did much work on boat motors. Oh and where would I find the serial number? It's a blue band motor
 
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I just pulled the cover and all I found was 1978 m-900 for the year of the motor but no serial number. How do I get parts without the serial number?
 
Water pump should be in stock at every dealer.----Same part since about 1963 or so to the late 1980's.-------Outboards and also the stern drive.
 
Most of the time you just the impeller.--------If you take that impeller with you and show it at the counter then most likely they would hand you a new one.-----Very common / popular item !!!
 
I ordered one on eBay today for $10. If I went to my boat stealership it would cost me $100. They are scammers! Thanks for the info
 
I got a OEM part for $10 and a Sierra aftermarket is $25 so I think I'm sitting good. A good quality part should last longer than 3yrs anyway so I'll spend the $20 to replace instead of $100 in 3yrs
 
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There is no overheat warning buzzer on your motor.---A new impeller every 3 years is good practice and good common sense.
 
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