Yamaha 115 HP idle problem

[Pat Davidson]

I have a 2001 4 stroke 115 hp that kills at idle constantly. Ran a couple of doses of Sea Foam thru engine and it seemed to help some. Now I am back to same old story, motor shudders and then kills, but will start back up immediately. Just won't idle very long at all. No problems at RPM's above idle. Any helpful comments?

 

[sdsaw]

Re: Yamaha 115 HP idle problem

Has the IAC valve ever been cleaned?
Seems like mine needs it about once every season lately
Worth a try and it's free.
Let some carb cleaner soak into the area with the tabs and blow it dry.
Keep the cleaner away from the o-ring

 

[Pat Davidson]

Re: Yamaha 115 HP idle problem

Is there something that causes this area to get sticky, I'm assuming this is a plunger type assembly? My motor purrs like a kitten unless I idle it for say one to two minutes. Then it will shudder and kill but will start right back up and idle again for another short period of time and do it all over again. Sometimes it will idle for quite some time before it will kill. I've trolled for salmon with it at idle for upwards of a 1/2 hour before it will give me any problem. I just hate having to restart my engine so much even though it starts back up right away. Hard on starters and the whole electrical system to have to restart so much.

 

[sdsaw]

Re: Yamaha 115 HP idle problem

I'm not really sure what causes mine to stick.
In fact, it doesn't appear to be dirty but cleaning it does help.

One other thing to check is your thermostat.
If stuck open, the motor will think that it is cold and run too rich when warm.
If the thermostat is stuck open, I'd change your oil because it might be over saturated with gasoline.

 

[Pat Davidson]

Re: Yamaha 115 HP idle problem

I checked and I do have gas in my oil. I do want to change my thermostat. Where is it located and how much of a job is it to change? I am still going to clean my IAC valve anyway. Is there any other condition that would cause gas to be in my oil? On a gas injected system is there any rich or lean adjustment. Oh, by the way, I really appreciate the help.

 

[sdsaw]

Re: Yamaha 115 HP idle problem

The thermostat is on top of the motor out in the open.
Remove the large plastic cover that is over the flywheel and timing belt.
There's a hose connected to the thermostat housing.
Remove the screws and lift off the housing.
No need for a gasket because the thermostat has the seal on it.
I use a thin layer of silicone on the mating surfaces when reinstalling.
Make sure that you are not getting salt build under the hose where the hose clamps to the housing.

The other conditions that I've read about that can cause gas in the oil is a motor that is "over-proped" and I believe that some of the 115hp motors have had the rings rotate and allow gas to get by them into the crankcase.
If you do a search for "making oil" you will find many discussions this subject.

There aren't any adjustments for you to make.
I believe that all the adjustments are made by the CPU and what the sensors are telling it.

You are very welcome for the thanks.
I'm just passing along info that I've learned here and there or experienced by owning one myself.
There is an absolute wealth of knowledge here that is archived so it is important that you respond back when you find the cure and somebody else will be able to use that knowledge to help them.

Scott