06 Yamaha 40 HP 4 Stroke will not idle

[nscott]

Hi everyone...this is my first post. I sure hope you can help me out with this one.

I have a 2010 Pontoon Boat that I bought last summer. The dealer sold me a Yamaha 40HP 4-stroke motor to put on it. The motor was a leftover 2006 model that I got for a great price. It was new and had the 3 year Yamaha warranty.

Last summer the boat ran perfect but we didn't put much time on it (5-10 hrs).

This summer the boat will not idle. Once I get it going it runs perfect above 3k RPM. If you drop below 2k RPM it starts to cough and dies. I have tried putting 5 gallons of 91 octane fuel in it and running sea foam through it. It started running a little better but this didn't last long.

Yesterday I added a bottle of Amsoil carb and choke cleaner. The bottle said to run this on every tank to deal with ethanol issues. I thought it was worth a shot as the sea foam didn't work and I wanted to try one more thing before taking the boat to the dealer. The bottle of Amsoil didn't help at all. If anything its worse now.

So I really fell I have an a dirty carb. I am guessing the idle jet is dirty. I know how a motorcycle carb works (idle jet = 0 to 1/4 throttle, needle works 1/4 to 3/4 throttle, and main jet runs 3/4 to wide open throttle) but on a motorcycle there is only one carb. This motor has 3 carbs. I am a little scared to tear into it. Should I just take it to the dealer or is there something else I can try?

Thanks for taking the time to read my post and any advice is appreciated.

Take care,
Nate in Kansas City, MO

 

[ssobol]

Re: 06 Yamaha 40 HP 4 Stroke will not idle

I had a new 09 Merc outboard. I bought it in July '10. The dealer said it was fresh out of the box. When I first got it, it would not idle very well at all. It would run ok at higher power after warming up, but would not idle at all when cold. After warming up it would idle ok for short periods before choking and quitting. Getting away from the dock was always interesting because the cold engine would not run at low speed. At first I thought it just needed some breaking in. But after running for a few hours it did not improve.

I took it back to the dealer, they said it was likely bad gas. A Merc repair shop also said it was bad gas. Tried new gas and marine engine cleaner (don't remember the brand). Still no improvement.

I told the Merc shop that I thought the carburetor needed adjustment. They said the carbs were set at the factory and it was against the law to mess with them.

Finally took it to the Merc shop and said just fix it. The guy said he tried running the engine and it would not idle. He ended up trying to push wires through the carb jets. One was open, but the other was not. He managed to open the jet. After that the engine ran great.

The guy said that there was probably varnish in the engine from sitting so long in the box. I tried to get it treated as a warranty issue, but no luck.

So maybe you want to have the same thing checked on your engine.

 

[nscott]

Re: 06 Yamaha 40 HP 4 Stroke will not idle

Thanks for the reply. Yeah I totally agree that docking a boat when it continues to die is pretty scarry!

I just hate to put the boat on the trailer and drive it to the dealer for repair. The boat is parked at the dock and the trailer is 40 miles away. Its a waste of a 1/2 of a day just to get it to the dealer. I wish it was a simple repair that I could handle.

Thanks again,
Nate

 

[pscrabber59]

Re: 06 Yamaha 40 HP 4 Stroke will not idle

I have a 2005-6 Yamaha F25hp that i bought used but had real low hrs and after installing the motor on boat experienced same problem like yours, in fact it would turn over fine but would not start&idle. When i called a friend about the problem he asked if i had done anything to the control box and i said i disconnected the two cables to remove a kink in one of the cables when installing the box, well to make a long story short i took the boat up to my buddie's place and we re-installed the shift&throttle controls and it was running sweet and have not had a problem since and that was two seasons ago.
Don't know if this will help you or not. Then again you still have a warrenty with the dealer so bite the bullet on losing a 1/2 day of your life in order to fix your motor.

Gd. Luck