90 yamaha 40 esd / 2 stroke / bottom carb

[90yamaha40esd]

My boat seem idleS fine but when i go it bogs down. Everyone has told me it is a fuel problem. I am pretty sure it is something to do with the bottom carb. There is no change when i pull the plug on the bottom spark plug but it is getting fire. I have replaced all the fuel lines in from the gas tank to the carbs, fuel pump, cleaned the carbs, put in new spark plugs, and checked the make sure the coil wasn't bad. Any suggestions????? It seems like it is catching too much air or flooding out. I have never adjusted the valves in the carb because I don't know how to. If you do please tell me. Could this be such a simple problem that I am overlooking?

 

[99yam40]

Re: 90 yamaha 40 esd / 2 stroke / bottom carb

Check the fuel pump diaphragm, probably a hole in it

 

[90yamaha40esd]

Re: 90 yamaha 40 esd / 2 stroke / bottom carb

The old one looked fine but still went ahead and replaced it anyway. No change. I am wondering if there is something with the bottom float/carb that is either flooding it or choking it. But I need to know how to set them because I have never messed with that part of it. I have cleaned the carbs though with a kit.

 

[99yam40]

Re: 90 yamaha 40 esd / 2 stroke / bottom carb

Did you take the carbs completely apart and clean with carb cleaner and compressed air?

 

[90yamaha40esd]

Re: 90 yamaha 40 esd / 2 stroke / bottom carb

yes. I am going to check compression in a little bit too but not sure what they should be at. That is what I am looking online for now.

 

[90yamaha40esd]

Re: 90 yamaha 40 esd / 2 stroke / bottom carb

Compression was good on all 3 too so now I really don't know what else could be causing it to bog down.... Any ideas would be greatly appreciated.

 

[99yam40]

Re: 90 yamaha 40 esd / 2 stroke / bottom carb

Are you sure you put the correct main jets back into the correct carbs?
My 1999 40 has a larger jet in the middle carb than the top and bottom.

Do you have a manual for your motor? It will have the procedure in it for adjusting the linkages and carbs that needs to be done after reassembly.

The pilot adjusting screws on my motor as set at 1 1/2 turns out from lightly seated.

Read this thread about adjusting carbs to see if it helps you any.
http://forums.iboats.com/showthread.php?t=366637


If you have good compression and spark, check the timing to make sure it is doing the correct things. If all is good then go through the carb again. all it takes is one small piece of trash to block a jet