90 hp mercury 2 stroke

[sar69]

I've got a 90 mercury 2 stroke oil injected that is very rough idling and smoking excessively . It runs good at wot. I've change plugs,fuel filter,drained gas out of tank put new gas in, new fuel pump diaphragm. I had to turn out mixture screw on each carb half a turn to get it to stay running. I'm not real good at working on 2 strokes so anyone with any ideas on what and how to check whats next

 

[jimmbo]

Start with a Compression Test.
What condition were the old plugs?
Does it have good spark at all cylinders? By 'good', I mean can it jump 3/8"

 

[sar69]

Compression test was at 90 to 100 on all 3 cylinders old plugs looked clean and wet

 

[sar69]

Spark seemed a little weak on all 3 cylinders

 

[racerone]

Put a number to it.-----A " little weak " means nothing to a mechanic.-----Does spark jump a gap of 3/8" ( 1 cm ) on this motor , yes or no ?----That is a test for finding if ignition is heathy.-----I would remove the exhaust cover as well.-----Allows you to inspect pistons / rings through exhaust ports.

 

[sar69]

A little weak means no it didn't jump 3/8" gap.

 

[racerone]

Some trouble shooting needs to be done.----Test stator as per a manual.