TKS Carburetor Question

[liquidwrench]

These carbs are new to me: they have what looks like and enrichment device from an outboard motor carb on them, and a cover of the spot that I expected to see an idle mix needle.
I wonder if the idle mix is adjustable, and how to trouble shoot a solution to the enrichment device adding fuel after the engine has started.
After looking at the spark plugs being sooty, and experiencing the poor idling I think that my 3.0L Mercruiser I/O has been running overly rich at low speeds.

Any advice on correcting this is much appreciated!

 

[JustJason]

Re: TKS Carburetor Question

There is a diode test for the enrichener but I don't have it handy, I believe Don does and maybe he'll chime in. The easiest way to tell if it's working is to listen. The tks carbs whistle until the enrichener is closed.
Pull off the spark arrestor and start the motor up (cold). If you look at the top of the carb you'll see a small hole where the tks circuit draws in it's air from. Thats the whistle hole. If you put your thumb over it when cold the motor should die out. Let it warm up 2 to 4 minutes, and the whistle should go away. If it does, you can put your thumb over the hole again and if everything is working then nothing should happen.
Boat plugs typically look sootier compared to automotive plugs because of the operating conditions and boating habits. They are a once a year maintence item. Just make sure you use the correct plugs (AC's or NGK's)

 

[Don S]

Re: TKS Carburetor Question

There is a diode test, but it's only for the electric fuel pumps on the V6 and V8 engines. Not the 3.0L which has a mechanical fuel pump.

There is a special tool for idle mixture adjustment through the hole in the tamper proof cover over the idle mixture screw. Being adjusted too rich is not likely.
How long after startup are you hearing the whistling from the carb? The book is giving 6 to 10 minutes before engine is warm enough to stop fuel enrichment. Plenty of time to keep the plugs sooty.

 

[liquidwrench]

Re: TKS Carburetor Question

Thanks for the guidance re: whistling, I had heard it but not realized the significance.
I checked again today after lunch. After four to five minutes running , the idle spped drops to appx 650-700, the whistle gets quieter but doesn't go away, then I run the boat up on plane and then return to dock; the idle speed is again faster like at the first cold start appx 950 rpm- too fast for the shift system, and a few minutes settling down is needed before the idle drops back to normal; That is something that should definitly not be happening!
The remote control/throttle and shift cables are returning to their proper positions and not affecting idle speed abnormally. (I don't think that the ignition timing varies, but I don't know how to check base timing on this engine, I guess that could cause un-controlled speed change. I will have to check into that.)
After I get this issue straightened out, I will likely get into idle mix adjustment, the boat was used and no service records are available.
I forgot to cover the hole with my finger to stall the engine-doh!

 

[Don S]

Re: TKS Carburetor Question

Here is some reading for you on the TKS system.

 

[liquidwrench]

Re: TKS Carburetor Question

! Thanks ! that is really helpful- all can be checked.