Mercury 402 not idle

[DutchMerc]

I have a Merc.402 40HP 2cil. 1carb, and i cannot let it run idle. it runs fine when i manualy keep the throtle open a bit, but dies if i let it go. I need to keep the second lever (warmup lever) on my controls half open to keep the motor running. When i turn the idle-screw on the carb, there seems to be no reaction, except the carb starts flooding when opened to far. Can this be a timing problem? How can i check this? The motor seems to run fine half throtle, just no idle....

 

[crem1]

Re: Mercury 402 not idle

Hi!

I'd start with the carburator, when is the last time you cleaned it thoroughly in solvent? Then of course new filter and bowl would help.

Alex

 

[garndawg]

Re: Mercury 402 not idle

What year is your motor?

Sounds like the carb is dirty. It's not too difficult to take it off and clean it.

Be sure to take the low idle screw and spring OUT and spray a lot of carb cleaner down in there. Run a pipe cleaner in there too (< $1 at walmart for a pack of 20). Be sure to LIGHTLY seat the screw when you put it back in and back out 1 1/2 turns from lightly seated.

Follow the link'n'sync in the FAQ after that...

 

[DutchMerc]

Re: Mercury 402 not idle

I don't know the year from the motor, ser.nr. is 9052668. I just bought this motor and I changed the waterpump and impellor, i got the impression that it has been a few years since the motor ran... I cleaned the carb out with some compressed air, not with cleaner yet. it did not look to dirty, so i thougt i might be alright..

 

[garndawg]

Re: Mercury 402 not idle

Nope. Exterior can belie bad things on the jets and small holes inside.

Soak that sucker overnight in carb cleaner and REMOVE the low speed idle screw spring when you do. Then blow some more carb cleaner through every small hole and such you see (wear safety glasses, carb cleaner in the eyes burns...), THEN compressed air through the passages and such.

Reseat the low speed idle as I said above and try to fire her up. Note that it'll take quite a bit of cranking to get it to catch at first. Choke it and advance the throttle arm a bit. You DID disconnect the throttle arm so you could move it manually, RIGHT?

 

[DutchMerc]

Re: Mercury 402 not idle

Yep, I took the advise and cleaned it again, realy firmly and accurate this time. The motor is running now, and has an idle speed from ~1120 rpm. in neutral. When the prop catches gear, the rpm drops to ~850, but keeps running. I think its O.K. now, except for some missfire (sounds like an extra kick from one cilinder???) Is this normal for a two-stroke veteran? (It seems to do this in neutral only..)