Motor kills under cold acceleration

[logman96]

Mercruiser 5.0L Thunderbolt Ignition
Serial number is not visible
Boat is 2004, not sure what year motor is

Before motor warms up it kills under almost any acceleration. Whether I put it in gear (forward or reverse), or have it out of gear but increasing throttle I have to nurse it up ever so gently or the motor will kill. Had the guy who winterizes the boat look at it and he couldn't figure it out. He increased idle, which maybe put a small dent in the issue but I don't think so - if anything maybe just causes the motor to warm up more quickly. This is an issue because I trailer the boat and backing it off the trailer and maneuvering around the dock under power is a problem, as is getting under way. At normal operating temperature this isn't an issue.

My very limited engine knowledge suggests to me a choke issue? But I don't have enough experience to know what to check. What do you guys recommend for troubleshooting or repair? Thanks.

 

[Bondo]

Re: Motor kills under cold acceleration

My very limited engine knowledge suggests to me a choke issue?

Ayuh,.... Welcome Aboard,...... Rather than just narrowing it to the choke, I'm thinkin' the Whole Carb needs a rebuild....

With a new accelerator pump...

 

[xltier]

Re: Motor kills under cold acceleration

remove your spark arrester and pump the throttle a bit and watch down the carb with it not running.you should see 2 squirts of fuel spraying down the carb as soon as u start to move the throttle.another slighter possibility is that the timing is set retarded to much.

 

[mpdive]

Re: Motor kills under cold acceleration

Check the engine when cold and make sure the choke plate is closed down. There should be only enough pressure to keep it closed and no more. I think you have an accelerator pump issue that is aggravating the situation. If it is failing, then you are going lean on any accelerator angle. This would be most prevelant and bothersome on a cold engine. A carb rebuild could kill 2 fish with 1 stone.

 

[Don S]

Re: Motor kills under cold acceleration

I would bet you don't have a choke on that carb and you have the TKS carb (Sorry to hear it if you do)
Does it work normally after the engine warms up? Water or trash in the carb is going to be a problem cold or warm.

 

[ENSIGN]

Re: Motor kills under cold acceleration

If you have the TKS carb it won't have a choke plate.You must let the engine warm up.This bright idea from mercruser was used to reduce emissions.you can either let it warm up or install the older style mercarb with a mechanical choke.(I did it on mine and she runs great!