99 Yamaha 115 2stroke-Carb Starting/Idle issue

MacGyver_74

Recruit
Joined
Jun 7, 2007
Messages
2
Hello all!

I have a 99 Yamaha 115 2 Stroke that is oil injected and carbureted. The boat was dry docked for 2 years with gas in the tank due to the severe drought conditions here in north Texas. We recently took the boat out, drained the gas and cleaned the carbs. The float bowls and jets were not in bad shape, but they had a small amount of gunk and laquer which I was able to easily clean out. I drained the tank and filled it with fresh gas and took the fuel line loose at the motor and flushed the lines with fresh gas.

Now, with a garden hose attached and the other end of the fuel line just laying in a portable tank, the motor started easily and idled smoothly.. Fast forward a week when it is in a slip on the water, and it does not want to start easily. It runs fine at WOT, but does not want to start or idle.. After warming up, it will start if you take it out of gear and throttle it up, but it won't start otherwise.

I noticed the other day that the primer bulb is not staying firm at idle, but even pumping it up firmly does not seem to help it start.

Summary of problems:

Hard to start on first start of day. Even though the primer bulb is solid at startup.

Mushy primer bulb after idling a few moments..

Only will start with medium throttle after it has been running a while



What I have done:

Cleaned the cabs and tank.

put new hose clamps on each part of the fuel lines and squared the hose ends where they may have begun to crack a little from age (I suspected air was getting in the lines).

Could this be the fuel pump or would it run as good as it does at WOT if the fuel pump had problems?

What do you guys think?
 

bugeyestp

Cadet
Joined
Jun 7, 2007
Messages
27
Re: 99 Yamaha 115 2stroke-Carb Starting/Idle issue

I had similar issue with my 94 150 yamaha. fuel pumps fixed mine. put on a new primer bulb first. primer bulb may break down and restrict flow. good luck
 

JUSTINTIME

Captain
Joined
Sep 2, 2006
Messages
3,284
Re: 99 Yamaha 115 2stroke-Carb Starting/Idle issue

check vent
check primer bulb
test the input and output of fuel pump
 

MacGyver_74

Recruit
Joined
Jun 7, 2007
Messages
2
Re: 99 Yamaha 115 2stroke-Carb Starting/Idle issue

Thanks for the advice!

How hard is it to get th pump off to change the diaphram? As inexpensive as they are, it may be worth changing it out anyway.
 

elktracker

Recruit
Joined
Jan 2, 2010
Messages
1
Re: 99 Yamaha 115 2stroke-Carb Starting/Idle issue

I also have a c-115 '99 model with carbs, not oil injected. I have a problem getting the unit to run smoothly, now it will hardly run at all. My primer bulb collapses, replaced same with a new one and the same thing happens. Fuel pickup in the tank must be blocked. I've been told it is probably Ethanol in the gas, leaves a residue at the bottom of the tank that attracts water, causing gunk, shellac and rusting in the engine. Ethanol is probably eating up my Fiberglass fuel tank which will need replacement as well as at a minimum carburetor rebuilding. Have not received an estimate yet for repairs. I guess I will be required to get my fuel in the future at a marina with ethanol free gas. If your motor will run fine on a portable tank, then I would repace the tank and start using ethanol free gas. I would like to hear what your solution is and I will also try and let you know my outcome.

Hello all!

I have a 99 Yamaha 115 2 Stroke that is oil injected and carbureted. The boat was dry docked for 2 years with gas in the tank due to the severe drought conditions here in north Texas. We recently took the boat out, drained the gas and cleaned the carbs. The float bowls and jets were not in bad shape, but they had a small amount of gunk and laquer which I was able to easily clean out. I drained the tank and filled it with fresh gas and took the fuel line loose at the motor and flushed the lines with fresh gas.

Now, with a garden hose attached and the other end of the fuel line just laying in a portable tank, the motor started easily and idled smoothly.. Fast forward a week when it is in a slip on the water, and it does not want to start easily. It runs fine at WOT, but does not want to start or idle.. After warming up, it will start if you take it out of gear and throttle it up, but it won't start otherwise.

I noticed the other day that the primer bulb is not staying firm at idle, but even pumping it up firmly does not seem to help it start.

Summary of problems:

Hard to start on first start of day. Even though the primer bulb is solid at startup.

Mushy primer bulb after idling a few moments..

Only will start with medium throttle after it has been running a while



What I have done:

Cleaned the cabs and tank.

put new hose clamps on each part of the fuel lines and squared the hose ends where they may have begun to crack a little from age (I suspected air was getting in the lines).

Could this be the fuel pump or would it run as good as it does at WOT if the fuel pump had problems?

What do you guys think?
 
Top