Evinrude 25 Model 25502b Backfire problem

M

macdaddy

Cadet
Joined
Dec 31, 2001
Messages
26
This this has been a nightmare, I have searched this site with no luck on an answer.

Problem: Backfiring out the exhust when trying to start, it will start but sounds like a shotgun, then starts and idles rough, pops and carries on then pops real hard and dies. When I pump the ball up it don't get hard.???

I have replaced coils, points (set at .20),condensers, pick up coil under flywheel, plugs (gapped at .30). rebuilt the carb cleaning everything. Checked compression 125 both holes, checked spark with a checker set at 7/16". Woodruff key is good.

I am at a loss here, help please
 
M

macdaddy

Cadet
Joined
Dec 31, 2001
Messages
26
Re: Evinrude 25 Model 25502b Backfire problem

Oh yea, new fuel pump, line and tank with fresh 50 to 1 fuel too.
 
M

macdaddy

Cadet
Joined
Dec 31, 2001
Messages
26
Re: Evinrude 25 Model 25502b Backfire problem

I have got it to idle, but in neutral and revinging it up, it revs fine and runs great for about 5 seconds and then starts backfiring and kicking again. Could this be reeds? If I bring it back to an idle it kicks and buck for a few minutes and clears up.
 
jbjennings

jbjennings

Captain
Joined
Jul 18, 2007
Messages
3,903
Re: Evinrude 25 Model 25502b Backfire problem

If your primer bulb doesn't get hard, either there is a hole in your fuel pump diaphram or your float valve isn't closing properly (more likely). It only takes a tiny piece of trash to keep it from seating properly and closing off the fuel. I personally don't think it's the reeds, but I'm not expert. I'd try to fix the fuel problem and go from there.
Good luck,
JBJ
 
tashasdaddy

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: Evinrude 25 Model 25502b Backfire problem

could be sheared flywheel key.
 
M

macdaddy

Cadet
Joined
Dec 31, 2001
Messages
26
Re: Evinrude 25 Model 25502b Backfire problem

lindy46 said:
Agree - when you put the flywheel on did you torque it down to 40-45ft.lbs?
Click to expand...

It is not a sheered key, or a dirty carb. The flywheel is touqued to 70lbs. I have checked that key at least 10 times.

As far as the float not seating, I have checked that 10 times also, take the carb off and blow in the hose, no air gets through.

Thanks anyway.
 
J

jonesg

Admiral
Joined
Feb 22, 2008
Messages
7,174
Re: Evinrude 25 Model 25502b Backfire problem

did you read the comments beneath the video?
 
W

wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: Evinrude 25 Model 25502b Backfire problem

Certainly runs like crap. Have you checked the timing? Backfiring thru exhaust is almost always caused by timing. Find the Joe Reeves method for link and sync and do it, if you haven't already.
 
M

macdaddy

Cadet
Joined
Dec 31, 2001
Messages
26
Re: Evinrude 25 Model 25502b Backfire problem

FIXED........

Now dont laugh at me but I had the dang float in upside down.

Thanks for all your help, you guys are great and so is this board.
 
W

wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: Evinrude 25 Model 25502b Backfire problem

Get yourself an OEM shop manual if you don't have one. If you have one, try reading it for your next repair adventure.
 
M

macdaddy

Cadet
Joined
Dec 31, 2001
Messages
26
Re: Evinrude 25 Model 25502b Backfire problem

Know good place to get an OEM?, all I can find are the Haynes and such.
 
W

wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: Evinrude 25 Model 25502b Backfire problem

Sometimes Ebay will have one. Also, kencook.com and several other web sellers may have them as well. If I recall, I got a shop manual for old Merc 150 Black Maxes from Mastertech. The third party books are junk, in my opinion.
 
You must log in or register to reply here.
Top