Outboard running poorly at idle

Wonderbloke · 13 May 2019, 19:30

All, looking for advice.. I have a 2005 Yamaha 30D 2 stroke triple.. runs like a dream WOT and fast cruising but at idle and just above, it sounds like metal on metal clonking and it vibrates loads..

Any ideas?

spartacus · 13 May 2019, 20:44

Spark plugs new and gapped properly?

On the engine there should be a fuel bowl. Check that. There's a mesh filter inside that, so certainly wouldn't do any harm to replace.

On the carbs, drain the fuel bowls. Any contaminants, then I'd look at a carb strip down and rebuild.

Wonderbloke · 13 May 2019, 20:57

Cheers Spartacus.. I replaced the plugs recently and gapped them right but may have over tightened?

Checked the fuel filter basket and had some crap in there, cleaned that out with brake cleaner and keeping an eye on it...

The carbs have fuel bowls? Okay.. will go looking for them..

It is a clonking sound..

Anyway, wish I could find a workshop manual for the engine!! Hey ho..

Thanks again..

spartacus · 13 May 2019, 21:20

Used to have a 25D outboard (mid 80s). These engines are bullet proof. On the carbs, the float chamber should have a brass hex drain screw (with slotted head).

Incidentally, I take it this is a pre-mix engine, not autolube?

Wonderbloke · 13 May 2019, 21:33

Nope.. Autolube 3 pot..

gtflash · 13 May 2019, 21:36

I had. Similar issue with my 2008 etec. Turned out to be a faulty injector.

Wonderbloke · 13 May 2019, 22:18

Ran ropey at idle but cleaned up as throttle opened? Would it clonk and vibrate?

Tim M · 14 May 2019, 00:53

Quote:

Originally Posted by gtflash

I had. Similar issue with my 2008 etec. Turned out to be a faulty injector.

No injectors on this engine.

Sounds like classic carb trouble to me, particularly if there was debris in the filter.

Carbs will need stripping down and cleaning and then reassembling. You'll also need to look at setting the idle mixture to get it running smoothly.

redken · 14 May 2019, 18:54

Where the carb butterfly is in the carb bore, there will be 2 or 3 tiny holes that deliver petrol at tickover and up to when the main jet kicks in. Gel or dirt can block these, when you clean the carbs make sure these are blown out.

Wonderbloke · 14 May 2019, 19:58

Cheers all!! I have watched a few YouTube vids and I feel confident I can successfully strip and clean the carbs.. put them back together again.... now that will be the fun part.. balance and tune them??? Erm.. lol.. hey ho..

Eric · 15 May 2019, 03:46

Usually the jet are fixed in a carb. The only adjustment will be the idle screw. I would boil the carb body to get rid of any gunge or dirt in the galleries.

beamishken · 15 May 2019, 04:38

Prety simple carbs no real adjustments just dont mess with the linkage lengths or throttle stops. a cheap ultrasonic bath is a good investment for cleaning carbs but usually a complete strip and removal of all the brass jets and a blow out with air line & or carb cleaner will sort
Idle screws are usually 1.5 turns out from lightly seated thats the only real setting there is

Wonderbloke · 15 May 2019, 16:36

Okay all.. just started the strip down but thought I would take a look at the plugs before I got the carbs off.. Plugs were new about 12hrs ago.. they are black.. is this normal? They already almost look like the plugs I took off and they had been on 5yrs.. 2 weeks use a year...

neil.mccrirrick · 15 May 2019, 17:30

No it’s not they should be a medium to light brown. Your fuel mixture may be too rich or there is no air getting to the fuel

Wonderbloke · 15 May 2019, 17:58

Well I am stripping down the 3 carbs.. First one looks clean.. fuel looks good.. no water etc..

Wonderbloke · 15 May 2019, 18:01

Noticed the top carb was slightly open when the rest are closed.. so they might need balancing.. could this cause the lumps at idle and it to run rich?

neil.mccrirrick · 15 May 2019, 20:27

Lumpy idle yes running rich no there is not enough air getting in the pilot jet may well be blocked as others have said

Wonderbloke · 15 May 2019, 20:46

Thanks for all the advice guys.. I have stripped down the top carb (which is way more than I have ever done before!) and there are 3 of them!
Fuel came up clean.. removed the 2 jets but there are 3 other bits of brass I cannot remove.. 1 look like it jets the fuel into the carb but no way of removing.. and 2 under a little rubber covered gasket on top of the carb.. trying to find a youtube vid of my carbs as I have no clue what I am looking at.. lol..
Final question, can I place the carbs in the ultrasonic bath with the brass bits still in?

neil.mccrirrick · 15 May 2019, 20:50

Yes you can use white vinegar to clean them as well it will de grease

Wonderbloke · 15 May 2019, 21:07

cheers Neil