1994 25 hp 2 stk yamaha precision blend 10 min good 5 min stalling then it runs good

evinice66

Petty Officer 2nd Class
Joined
Feb 15, 2008
Messages
181
hi! i just bartered work for an outboard, i love this yamaha 25 2 stroke precision blend motor but it only runs good for maybe 10 minutes then it starts to die, the only way to save it is to pull the choke out for a second and then it revs back up and wants to die again, if i do this for 3 or 4 minutes it will start to run good again!

i dont get it!!!

a couple other things about this motor are that it runs a little ruff in neutral ( only have run it in neutral so far) when it is in lower rpms, could this be because it has champion plugs in it when ngk is recommended? i read these motors are nice for trolling slow which is what i need and am excited to do! i also somehow broke the electric start on it. what would be the first thing to do to see what failed? i

i am really impressed how quiet it is, and im really looking forward to straightening out the problem because the salmon are in the harbor!!!!!!!!!!!!!!!!!!

i ran it for 15 min with seafoam and it seems to smooth out a little, i havent had time to take it to the lake to run it wot yet.
will seafoam fix my motor? im definitely a big time seafoam fan! thanks for ANYTHING you can tell me about my new favorite toy!!
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: 1994 25 hp 2 stk yamaha precision blend 10 min good 5 min stalling then it runs g

Check compression on all cylinders to start out with and then check spark on all cylinders with spark tester.
next is timing and then check fuel pump.
pull and clean carbs properly and adjust like the service manual states before you pop a piston from running lean and hoping seafoam will fix it
 

evinice66

Petty Officer 2nd Class
Joined
Feb 15, 2008
Messages
181
Re: 1994 25 hp 2 stk yamaha precision blend 10 min good 5 min stalling then it runs g

Check compression on all cylinders to start out with and then check spark on all cylinders with spark tester.
next is timing and then check fuel pump.
pull and clean carbs properly and adjust like the service manual states before you pop a piston from running lean and hoping seafoam will fix it

thanks for the warning, i appreciate it, have you heard of something like this before?
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: 1994 25 hp 2 stk yamaha precision blend 10 min good 5 min stalling then it runs g

No not really, usually if running bad it stays that way.
But it never hurts to make sure motor is sealing, and sparking properly and timing advances when you 1st get it.
If all of that is good you are left with fuel.

Would be a good idea to make sure oil system is working properly, could be motor is seizing up from no oil.
But sounds like fuel problem to me if you have to choke it
 
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