Different Part Numbers for both SLOW and MAIN Jets?

I have a problem with my 2000 model Yamaha 115 (115TLRY) where it will not idle, even with the idle set at 1200RPM. The boat must be choked and the throttle set to about 3/4 to start, even when warm. I replaced the fuel lines and primer bulb. The bulb will now pump to firm, but will not stay firm while the motor is running (usually 30 minutes later it is soft, but not deflated). Last weekend, the boat died at idle while waiting to put it back on the trailer and would not start (fun in a crowded marina in a crosswind). The motor refused to start, even when choked and the throttle set high. After literally 10 minutes of trying, the motor caught and poured white out white smoke and then LIMPED onto the trailer.

HISTORY:
The motor, even when new from the showroom floor, has never idled very well.
However, due to a severe drought here in Texas in 2007, the boat (A 25' pontoon) set suspended above drive land in it's boat stall for a year and the gas in the carbs turned to varnish.

I tore down the carbs and thoroughly cleaned every orofice I could find. I then re-assembled the carbs and set all the pilot screws to 1 and 1/2 turns each as the manual suggested.

The boat started and ran (whereas before it did not). However, it STILL would not idle lower than 1200RPM and even then frequently died at idle.

MY PLAN:
After reading virtually every post on the board concerning the 115, and given the age of the motor, I am going to replace the fuel pump an again rebuild the carbs. However, this time, I would like to replace the SLOW AIR JETS as I believe they could be responsible for the idle prpblem and starting over new might be the best option.

I did notice when looking at the parts breakdown that there are two different SLOW AIR JETS listed. A number 78 and a number 82. The same appears to be true for the main jets (#176 and #180).

My questions are these:

1) How do I know which jets to order?

2) Is it possible my idle problems from the very beginning have been due to the wrong jets being put in the carbs from the factory (I presume the different jets are for different altitude usage?)?

Thank you very much in advance for your help. I really enjoy this board and am glad to have found you all!

My boat is used at Lake Ray Hubbard, just outside of Dallas, Texas. The altitude is only slightly above sea level so I don't think that is a factor.

There should be a number stamped on your original jets, it may take a magnifying glass to see them. It does sound as if the motor may be running lean at idle so if you dont find any kind of restriction in the jet orafice you may want to try the larger jet. which will be the bigger number.

[Hamfisted]

How's it do with the choke on ....

If you pull the manual choke out half way will it idle down lower? Unless the idle air jets were physically damaged somehow, I don't think they are your problem. Did you soak the carbs in a cleaning solution when you did the tear down? Blow them out with compressed air? New base gaskets installed? You don't see any fuel bubbling up into the throats do you? (Float level too high...).




- Mike

If you pull the manual choke out half way will it idle down lower? Unless the idle air jets were physically damaged somehow, I don't think they are your problem. Did you soak the carbs in a cleaning solution when you did the tear down? Blow them out with compressed air? New base gaskets installed? You don't see any fuel bubbling up into the throats do you? (Float level too high...).




- Mike

Mike,

Thanks for your reply. I have never tried to pull the manual choke on the motor half way out, but that is a good suggestion.

I did soak the carbs in cleaning solution, but the shop where I worked on them did not have compressed air. Also, I reused the old gaskets as they seemed to be in usable shape.

This leads to my next question, where can I get a carb rebuild kit that comes with all the gaskets and parts I need. The prices I have seen around the web seem to be much less expensive than buying each piece individually.

I put new plugs at the end of last year so I am hoping that putting a new fuel pump and going through the carbs again fixes this problem.

Thanks for your help! This is really nice to be able to share in your collective expertise.