1996 Yamaha 225 2.6L- Rough idle, surging/stalling

dmorela

Cadet
Joined
Mar 6, 2008
Messages
12
Hello everyone. I am experience hard starting and rough idling. The engine surges and eventually stalls out at idle. It runs perfect at higher rpms and hits 5000 rpms no problem.

Below is what I have done (in order). I'm running out of ideas and would appreciate any feedback.

1. De-carbed with seafom- both "shock treatment" method and by spraying directly into the carbs. Replaced plugs.

2. Cleaned engine fuel filter and replaced fuel/water filter.

3. Replaced both low pressure fuel pumps. I belive there is a 3rd pump that is located under the Prime Start system (the one with the red switch located above both low speed pumps). I did not dissassemble this or inspect it.

4. Took apart all 3 (dual) carbs, cleaned, and reassembled. One of the jets had a little gum, but once cleaned it did not improve the idle.

The motor still stalls out at idle. There is a lot of fuel in the silencer cover and once the motor is warm and it stalls out it is hard to get it started again. Almost like it is flooding.

What should I try next?

One of the weekend mechanics at the marina took a quick look at it and said he thought the issue was isoltated in the 2nd carb. He sprayed carb cleaner in each of them and noted that the motor bogged down when carb cleaner was sprayed in the #2 carb. He thought this is a carb issue and not a fuel/pump issue.

Also, the primer bulb is new and remains hard the whole time.

Thanks for taking a look. Looking forward to hearing some ideas. I was determined to fix this myself but I am getting discouraged.
Prime start? Choke solenoid?
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 1996 Yamaha 225 2.6L- Rough idle, surging/stalling

need a model number,
the 96 2.6L 225 does not show to have prime start but the 95 does.
if the engine has a primestart pump with the twin solinoids and its diaphram ruptures it dumps fuel from the top cab bowl into the enrichment circuits and the engine runs very rich and can stall.
 

dmorela

Cadet
Joined
Mar 6, 2008
Messages
12
Re: 1996 Yamaha 225 2.6L- Rough idle, surging/stalling

Thanks Rodbolt. I won't be able to get the model number for another day or so but attached is a picture of the carb stack. It must be a 95- appears to have the prime start system you describe.

Also, when i remove the silencer cover after it has been running for a while I notice that fuel is pooling in the barrels of all 3 carbs. Does that symptom sound consistent with a ruptured diaphragm in the PS system?
 

Attachments

  • Carb stack Port.jpg
    Carb stack Port.jpg
    145.1 KB · Views: 0

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 1996 Yamaha 225 2.6L- Rough idle, surging/stalling

yep, its a 90 to 95 version of the prime start on a 2.6L.
yes the symptoms are about what you have if the diaphram ruptures.
 

dmorela

Cadet
Joined
Mar 6, 2008
Messages
12
Re: 1996 Yamaha 225 2.6L- Rough idle, surging/stalling

Thanks. Can't wait to check it out tomorrow. Will report back with the outcome.
 

dmorela

Cadet
Joined
Mar 6, 2008
Messages
12
Re: 1996 Yamaha 225 2.6L- Rough idle, surging/stalling

Rodbolt YOU DA MAN
Replaced prime start diaphragm and all is well.

I think I'll go fishing now.
 
Top