Merc engine tickover prob ???

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itsonlymoney

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I have a Bayliner 2655 (99) with a merc 220hp Thunderbolt (carb) engine.
Since I have had the boat the engine will not tickover from cold you have to advance the throttle to 1200rpm or so, is this normal ?
Also when revving the engine when cold it spits and misses a bit but is fine when up to temp, is this timing, fuel, auto choke or something else ?
(Runs absolutely fine when up to temp,ticks over no probs revs no probs)
Any advice very welcome
Regards - Ian
 
Having had the same boat myself with the same problem, the automatic choke probably needs adjusting, it sounds like it comes on too much and causing the engine to stumble. there is no automatic fast idle during warmup so its normal to raise the idle to get it up to temp. Its a big lump and takes a few minutes to get warm enough for the fuel to vaporise properly.
The timing should be OK as there are no moving parts to wear, and it runs well when warm.
Remove the flame trap and open the throttle when cold and you should see the choke flap snap shut, then when you start it the flap should open slightly as the air gets drawn in, you should see it creep open. If its a manual auto choke it will have a metal box on the starboard side of the carb with a rod coming up out of it which opens the choke flap as the hot spot on the inlet manifold warms up and heats the bi-metal spring, this can be bent to adjust it.
If its an electric choke then adjust the round cover with the 3 screws and a + - scale, and an electrcal connection on it.
Adjustments must be done cold and with the engine off.
 
Wow, thanks for a very informative reply. Just to clarify am I right in thinking that therefore it will not tickover without advancing the throttle ? Also should the choke flap be bent more open or shut ?
Ian
 
I had a similar problem on my last Searay - 4.3V6 job. On that the solenoid didn't function to close the choke flap at all. Didn't fix, just changed boat ! (but not because of that). Fast idle for a few mins worked fine, late May - on no probs anyway.
Cheers,
T.
 
My 2255 has the Mercruiser 5.0LX (same/similar engine also with carb) and it started playing up like this right at the end of last season.

I suspected the choke might be sticking but didn't have time to sort it out before draining it down for winter so it's on my list of things to do in the next week or two.

I will add my thanks to Spannerman for his comprehensive and timely advice.

What a wonderful institution this forum is /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif
 
If its the mechanical choke, you need to carefully prise up the metal cover at the side of the carb to expose the coiled bi-metal spring, you then can carefully ease the splined spindle out of the two forks it sits in and rotate it so that there is less tension on the spring pulling the choke 'on'. This will mean that it doesn't close so hard and opens earlier, it could take a few tries. Test the choke flap when cold by watching to see if it flips from full open (vertical) to nearly closed when you open and close the throttle once to release it.
If its electric its much easier, just slacken the 3 screws and rotate the cover towards minus on the scale.
Yes you need to give it some throttle to raise the idle speed when cold, as there is no fast idle on these carbs, that feature is only on the injection motors.
 
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