Need Help With Mercury 25 2-stroke

[tmkilburn]

Been trying to get this thing running for a while. It will only idle if I hold down the blue primer button on the carb. As soon as I let up on it it dies after about 5 seconds. I'll outline what I've done so far below.

-checked spark/changed plugs
-changed gas tank
-changed fuel lines
-bypassed original fuel filter and put an in-line
-rebuilt and replaced all carb gaskets
-checked compression 115 on both cylinders
-changed gas

Any help would be much appreciated.

 

[Barnacle_Bill]

You don't say what year it is but I would check the fuel pump. Diaphram may be shot

 

[tmkilburn]

You don't say what year it is but I would check the fuel pump. Diaphram may be shot

It's a 2003 model. I Don't think its the fuel pump because as long as a hold that blue primer it wil. Run. I don't evenhave to pump it. Just hold it down and it will idle forever.

 

[quicktach]

Sounds like a carb problem...engine starved ... details on carb ?

 

[tmkilburn]

Sounds like a carb problem...engine starved ... details on carb ?

Went back through the carb and could barely see light through the idle jet. Ran some broo straw down it and sprayed it good with cleaner. Motor is now idling good but it is now bogging down when I go from slow to WOT. If I have to pull the carb again I'm going to go crazy.

 

[MH Hawker]

Run some sea foam through it.

 

[tmkilburn]

Messed with the mix screw and turned up the idle a bit. Its revving up no problem now and hopefully it continues to do so.

 

[oldman570]

When setting the idle mixture jet, you will need to set it a 1 1/4 turns out . Then with the motor warmed up, and on the water, you might need to adjust it in or out a blade width till the motor will run at its best when at idle and at WOT. The use of Sea Foam is highly recommended at first start up after the motor has set, and fogging spray should be used when the motor is going to be setting for long periods . JMO
Oldman570

 

[CharlieB]

I see you have found your lean idle problem. Typical two stroke carbs do not have an accelerator pump which requires the idle mixture to be adjusted extensively rich to allow enough extra fuel for the motor to accelerate when under full load. Often this is almost 1/4 turn out from any 'Best Idle' setting. Make small changes, just the width of the screwdriver blade-slot then test acceleration in gear. Any hesitation, lean cough, or bog, indicates it needs even more fuel. Tweek/turn it out another slot-width and retest. Repeat til you get instant throttle response, a perfect holeshot. Any more than this just wastes fuel and shortens spark plug life.

Next time you clean a carb, start by turning IN the idle mixture screws while counting the exact number of turns and using an imagined 'clock-face' of where the blade-slot was, so once finished you can re-install the needle almost perfectly where it originally was. It can save you massive time making adjustments once finished