Yamaha 115 HP 2 stroke dead spot

[Yamafan]

My father in law's 115 2 stroke has a dead spot between idle and 2000 RPM. Just the range we need when docking. Is this common or what can be done short of trading it in. Above 2K rpm it runs like a dream. To get it to 2000 we need to push the choke repeatedly or very very gently accelerate through the range. Dealer has no idea.<br /><br />Thanks

 

[Yepblaze]

Re: Yamaha 115 HP 2 stroke dead spot

Many carbs (especially japanese motorcycles) have a pilot jet. It can sometimes be found next to the main jet and this is where I would start looking. If these carbs do not have a pilot jet, they should have a system within the carb for the transition from idle to main metering system. This may be a set of bleed holes near the butterfly as it would be coming off idle.<br /><br />Now if this is a motor less than a few years old it would have some very safisticated electronics that may or may not be able to be remapped with the aid of a computer plugged into the motors control system.

 

[my new fishmaster]

Re: Yamaha 115 HP 2 stroke dead spot

I am not sure but I would take the fuel pump apart see if the rubber is turned over. They make kits you can buy the new rubber thingys. I belive many outboard owners have the same problems engine is hard to keep primed,you need to choke in order to keep her running.

 

[Bruno]

Re: Yamaha 115 HP 2 stroke dead spot

I think Yepblaze is right,it sounds like its having trouble getting off the lowspeed jet to the main and vise-versa.I have one of th HPDI 150's so I can't look at mine to tell you how yours is set up.You should try to find another marina with a skilled tech,it sounds like your dealer doesn't want to spend the time.You should alsa try a compression check in case one cylinder has maybe scored and dropped off enough to cause your tuning to change.Do this first because it's easy to do yourself,and you'll have a better idea if you run into a mechanic that sets up your carb,and charges for a rebuild(cynical eh?)<br />Hope I help<br />~Bruno

 

[Gaolei]

Re: Yamaha 115 HP 2 stroke dead spot

I had the same problem on a 2005 115 Hp with only 45 hours. It would run fine above 2000 RPM but would not run under 2000.

I took the Carbs off and cleaned them out with carb cleaner spray. In doing that I found the real problem. On the top of each carb there are teo large brass screws. Remove them. You will see 3 small holes. Chances are they are plugged. These are the idle jets and the transition jets used to smoothely get the motor up to the speed where the main jets begin to work. I cleaned them with the carb spray, reassembled and ran the engine. It now worked fine. You could also use a copper wire to help clean the holes, but don't use anything harder or you will damage them.

Actually, you will only have to remove the upper carb to clean the lower carb. The screw is on the top of the carb and easily removed with the carb in place. You can look in the upper carb idle jets without removing it from the engine. Just remove the inspection port screw.

 

[rodbolt]

Re: Yamaha 115 HP 2 stroke dead spot

the above description is actually totally wrong.
post the model number of that 115 as there were 2 versions of carbs.
but in either case Yamaha never used a transition.
they did use a pilot air and a pilot fuel jet.
the air jet is located at the fwd end upper part of the venturi and the pilot fuel jet is located in the fuel bowl.
the holes under that large brass plug are simply holes.
have nothing to do with anything else.
however if they get plugged idle will be affected.

 

[Gaolei]

Re: Yamaha 115 HP 2 stroke dead spot

The engine would not idle or run under 2000 rpm. The holes were plugged. I cleaned the holes. the engine idled and transitioned to high speed. The holes are located at the throttle plate venturi boundry, Idle area. There is no other jets in the area.

 

[Gaolei]

Re: Yamaha 115 HP 2 stroke dead spot

The engine would not idle or run under 2000 rpm. The holes were plugged. I cleaned the holes. the engine idled and transitioned to high speed. The holes are located at the throttle plate venturi boundry, Idle area. There is no other jet in the area.