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1999 25 HP Mercury

wintys

Member
"My friend has a 1999 25 hp Me

"My friend has a 1999 25 hp Mercury with 80 and 85 pounds of compression.
He just re-built the carburetor, it’s got good fire and gas; could this low compression be the cause of it not wanting to crank?
What should the compression be?"
 
"Well ideally you want about 1

"Well ideally you want about 125 psi,but any thing over 100 is reasonable .you need good compression and SUCTION[terrible description]to get air and fuel into the motor,past the reed valves, and up into the combustion chamber.no suck,no go.i assume when you say,"not wanting to crank"you really mean,not firing and starting up?"
 
"Yes sir; you are correct; not

"Yes sir; you are correct; not starting up.
Sorry, I meant the spark plugs are firing (good spark)
I didn’t think about without enough compression, or seal it couldn’t pull the fuel in to the chamber.
Thanks budgie, I pick up a little more each time I get on here"
 
"Yea Jeff, after a little more

"Yea Jeff, after a little more looking and investigation your right she’s whipped, the kid bought it from his boss; I’m hoping that’s all it needs.
He and his Dad are going to break it down and try to rebuild it; he’s a retired machinist and pretty sharp.
I want to get in on the rebuild myself; I have an old 25 Merc. I knocked off on a stump in the river last year I want to rebuild, just have been tied up with my Twins.
That’s twin 250 Mainers, I just love’em. LOL
Thanks Jeff, I will probable be back in here asking yea question about the 25 and the twins.
Thanks to all of you WT."
 
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