Motor idles bad but great when underway? - HELP

[Chanlo]

Hi,
My first post (I just joined).
I have a Quintrex 445 Dory converted to centre console.
It has a Yamaha 40 on the back.
I have owned it since june 09 and it was fine but then start of this year it has started spluttering when on idle.
I took back to seller and they serviced it and said it had a bit of junk in the carby.
(Honestly is ran better but still slightly splutered)
I moved tank to front, added fuel filter and new squeeze bulb. I cleaned the tank out, only use premium fuel and even swapped to another tank and still same problem???

When it is on idle it also stalls sometimes, sounds like it misses a cylinder.

Any help would be appreciated
Cheers

[captain rednut]

another properly done carby job should fix it nicely.
cheers jim

[Steeler]

Chanlo

If you are sure the fuel system is not the problem it might pay to pull the plugs out and just check for any signs of water ingress.I have had a few Mercs that showed similar symptoms ( providing not a fuel delivery issue ) and as it turned out it was the first symptoms of a failing bottom power head seal allowing a small amount of water into a cylinder and causing issues. Might pay also to have a compression test done to ensure there all about even, if one is significantly low it can be more noticeable around idle RPM's.

Steeler

[GB61]

Have you tried adjusting the air mixture screw , I would hope it was done when serviced ? Friends 30hp Suzi 2 stroke needs the air mixture kept just so, otherwise it has rough idle . Yams with single carb are hard to keep well tuned as well ,in my experience (limited)

[Chanlo]

Cool thanks guys.

When i had it serviced he changed plugs (after i already had changed them and told him not to use new ones...they dont listern... charged for new plugs also and kept the new ones i put in)

They also tuned carby and said it had a bit of gunk under it and they cleaned that also. Recon it took them 1 hour to get carby right!.... Would it go out of tune in 3 months?

The other week it ran fine then friday it was playing up again. I have used different fuel companies also.

Do they have injectors could it be that?

Last service and tune cost me $360 and i cant afford that again and want to go fishing in the Pirtek Challenge this weekend but dont want to wreck my boat trying!

Can i do a compression test myself, my brother in-law is a mechanic and will have access to equipment.

[Aunty Jack]

I had and older model mer'c with the same problem.
But I got lucky on the fix it side of things.
I took of the air cleaners housing, brought the motor up in rev's,
then with a large lint free cloth, eg tea towel.
Placed it over one carbbie at a time,any crap gets sucked streight through.
It took a few times to get it cleared but it worked for me.

[STUIE63]

how long are you leaving the boat between uses
Stuie

[Chanlo]

how long are you leaving the boat between uses
Stuie

lucky to be 2 weeks.
I usually go out on a weekend out to sea or in estaury. Always salt water, always flush it with fresh afterwards.

I will try the suggestions tomorrow and let you know how it goes.

(Also check out my 49cm bass in biggest bass topic... my second bass ever!:) )

[STUIE63]

just thought it might be 2 stroke mix drying in the carbies but if every 2 weeks or less then not that
Stuie

[Jarrah Jack]

Don't know too much about this sort of problem but Noelm should be along soon to sort you out. One thing I've picked up is not to use premium fuel, your motor will be more than happy with the regular stuff.

[supa29]

I had and older model mer'c with the same problem.
But I got lucky on the fix it side of things.
I took of the air cleaners housing, brought the motor up in rev's,
then with a large lint free cloth, eg tea towel.
Placed it over one carbbie at a time,any crap gets sucked streight through.
It took a few times to get it cleared but it worked for me.

just read your post can you pm me how you do your tea towel trick cause i got merc and sounds like that might fix mine.

thanks supa.

[dreemon]

Try this, pull the air cover off, tilt the motor up and squeeze the primer bulb hard then you can see if fuel dribbles out the front of the carb/s, if fuel does come out you have a prob with the needle and seat, either it sticking or a small partical keeping it open,

mine was doing the same, really bad idle but fine at wot and using a hell of alot more fuel, Good luck with it, sometimes when wot you can hit the choke to pull the crud through, sometimes. . . .

[Chanlo]

My brother in-law (car mechanic) and I had a quick at it last night. Brens boss said to check the fuel filter inside the motor casing. We did this and notice a bit of junk and water inside it. We cleared this out and cleaned it, started her up and she ran alot smoother on idle but did miss occasionally but still 100% better than it was before. I am changing inline fuel filter on sat and will test it again then and if she still aint right do a few more of the test you guys mentioned

Thanks to everyone for your help.

[Jasinex]

just had the same issue fixed on mine... ran perfect but started to idle with a splutter and miss and then became hard to start.. the Idle jets in the carby were blocked ( they have 2 jets per carby idle and run) get the idle ones cleaned/replaced and it will fix your issue

[Chanlo]

just had the same issue fixed on mine... ran perfect but started to idle with a splutter and miss and then became hard to start.. the Idle jets in the carby were blocked ( they have 2 jets per carby idle and run) get the idle ones cleaned/replaced and it will fix your issue

We (me and Bren) talked about a small amount still being present in the carbie chambers and cleaning them out on saturday if it still wasnt purring like it should be.