2003 Mercury 75 ELPTO, 2-stroke, Ser 0T686115 - Thermal switch?

[thilltony]

Helping a friend with his 2003 Mercury 75 two stroke engine.

Does this motor have a thermal air switch?

Starts and runs fine, but runs rich at idle. Did all the obvious stuff, including rebuilding the carbs. Good compression, good spark, pinched off the enrichment valve, just in case it was leaking, but still running rich at idle. Turned the idle mixture down, and it stalls.

This acts just like a stuck thermal switch on a 150 HP, but I don't know if the 3 cyl has one.

Does anyone here know if the 75 has a thermal switch?

Thanks.

[JOE54]

no sir does not , check pulse pump diaphram, and timming

[thilltony]

Thanks for the reply, Joe.

I still wonder if his fuel enrichment solenoid is leaking. That would present with the same symptoms. I wonder how carefully that line was pinched off. I'm thinking that may be the problem.

I appreciate the info. That helps me eliminate one more thing. Now I have a plan when I look at it in person.

-Tony

[JOE54]

not seen many leak but a lot not working, those mtrs run very lean at idle, idle timming is critical also, check it out, report back

[thilltony]

Got the boat here, and everything is checking out, so far. Enrichment valve is not leaking, compression, timing and spark all look good.
I figured it was simply idle mixture, but at idle, she is either rich and smoky or lean popping and stalling, but still smoky, somehow.. There doesn't seem to be any proper setting.

Just looked at the service manual, and it mentions the bleed system could be blocked up, causing poor idle quality. I'm not familiar with this system. Could this cause it to idle poorly?

The other thing I'm wondering is float height adjustment. I know Mercurys tend to be touchy about float height.

He's had this to several others before me, and none could figure out what was going on. In the recent past, he has had stator, trigger, coils and carbs rebuilt, but it still idles poorly. I'm going to take it on the lake and try to tune in the carbs again, as I only had about 1/2 hour to try earlier.

Let me know what you guys think. Thanks.