Mercruiser Carb without choke ??

jfkal

jfkal

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Still trying to make sense out of my Mercruiser setup.
can anyone identify the carburator in the pictures?
Does not have a choke, nor does it seem to ever having had one.
Merc manual talks about choke valve and electric heated adjustment mechanisms etc.

Help appreciated :-)
Thanks
 

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Not seen your set up but if the manual talks about electrically heated mechanisms, the there may not be a choke in the normal sense of a flap valve restricting the air flow to get a richer mixture. It may instead be a heater mechanism which dumps additional fuel into the air flow to give a richer mix. And that'd be buried somewhere in the carb, not sitting in the airway like a choke valve. Are there any wires running to the carb? How is the choke activated? Is it by pushing in the key whilst turning the engine over?
 
Very unusual for the Mercruiser. Never seen this before. What engine is it ?

Normally they have a thermo controlled auto choke.....great when they are new but most disconnect them at the actuator mechanism on the side of the carb and simply start from cold using the pump throttle lots of time before turning key method.
 
Hi Duncan,
thanks. But maybe I was not very clear. The original manual talks about the choke system. My carb does not havr any of this, which is really odd.
 
Hi, yeah, that is my problem. Never seen this before. Funny thing is engine starts cold without a hitch. However has other problems, such as fast idle, dying when idle is set lower. Not returning fully to idle coming back (in gear) form cruising RPM.
Engine is a 5.0L TKS made in 2006. There are no maker plates on the carb :-(
 
I have had exactly the same engine before, its the TKS (Turn Key Start) model mercruiser used in the early -mid 2000s . it has an electronically controlled choke like function that regulates the air/fuel ratio. It is an electrothermally controlled air valve. when the engine is started and you will clearly hear this as a hissing sound from the carb area , rpm will be about 1000-1100 range, then as soon as the engine temp nears about 75 degrees centigrade (usually about 7- 10 mins depending on the ambient temps) the hissing sound stops from the carb area and your rpm will fall to about 650-850.
Mine worked like clockwork in the 3 years i had it.
 
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Ah...it's a TKS.
Yeah these are different from the traditional sense of the choke. White mans magic. They aren't without their problems.
I can't quite remember the exact details but your symptoms are the standard issue...there was a service bulletin and a fix for the problem issues from Merc. I'll ask the local guy next time I see him.
 
Think it's to do with the enrichment circuit or temp sensor, just thinking about it. One of them needs replaced and was done under warranty on a recent 3.0 tks of my friends.
 
Thanks. I will have a closer look at that area then. Anything else springs to you mind or when you see the local guy do let me know. Appreciated.
Cheers
 
Hi Jfkal

I spoke to the Merc dealer this evening.
He said your symptoms are a common issue (unnoficially)...
He said that it is most likely the mixture screw needing adjusted and set up.
This is not as easy as you might think....it is designed to be tamper proof for the average punter...apparently it is hidden by a cover or casing that needs to be removed by a special Merc tool...or some initiative thinking (also unofficialy)
Others on the inter web have also referred to this and seem to go down the route of replacing the enrichment control. This sorts the problem, but apparently unesessary.
Best of luck and let me know how you get on.
 
Thanks a ton. Got the TKS manual in the meantime 106 pages, arrgh. Whover developed that should be sent to 20 years hard labor. The 1960ies Beetle had a similar system using one wire. Worked like a whistle. Why keep things simple if you can do it complicated. I will keep you posted on the progress or else the lack of it.
Cheers
Joerg
 
I've got a 3.0TKS and this started fine, but would not always idle when put into neutral, and then cut out at the critical moment coming into moor, or would idle too high when put into neutral, it was a right pain. I noticed on mine that the bracket where all the control cables fit onto moved slightly as the engine rocked when idling lumpily sometimes. This movement was enough to pull the throttle cable thus increasing revs by a few hundred. I made a bracket to brace this to the exhaust riser. I then cut off the cover over the mixture screw with a Dremel and some twisting with pliers, and adjusted it to run slightly richer, and ever since it sounds and runs so much better.
 
Must be due to some play in the throttle control, which I have discovered as well. I will try to fool with the mixing screw also. Thanks for that.
Also found two orphaned cables in the vicinity of the carb. I will post pics next couple of days. I am sure they had some purpose.

Cheers
Joerg
 
Changed throttle and shifter cable. Readjusted everything. works better now. Still idles too high out of gear but behaves in gear.
 
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