2007 mercruiser 5.0 has spark and fuel but won't start.

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Chudwick

Cadet
Joined
Apr 10, 2016
Messages
26
Hello. My boat has been giving me trouble with stalling out at idle and acting sluggish when accelerating. First thing we did was rebuild the carb and that didn't fix anything. We then popped off the distributor cap and saw it was in bad shape so we replaced it and it ran like a champ. That was 3 days ago. We went down today and it started right up, ran for 3 seconds, and died. Figuring the carb was flooded I let it sit for a while and it fired up. I ran the rpm's up to 1500 to make sure it wouldn't die again but it did anyway about a minute later. Next step was we replaced the wires and pulled the plugs out and regapped them all and after that it won't even attempt to kick over. It has fuel and spark. The spark is orange and doesn't look good. Could a weak coil be the cause of this problem ?
 
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Chudwick

Cadet
Joined
Apr 10, 2016
Messages
26
I just went down there and shot starting fluid down the throat of the carb and it didn't do anything.
 
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Markrhoyt

Cadet
Joined
Sep 1, 2011
Messages
20
Was the spark orange before you gapped the plugs?
It should be a bluish white. Coil may be going bad but usually it either works or doesn't.
Check to see if the filter has water in it. An engine will run for a few minutes with water in the filter but then it will die or sputter until it sits for a few minutes then it will start again. The paper in the filter is designed to swell and slow fuel flow so you don't get a big shot of water into the engine.
 
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Chudwick

Cadet
Joined
Apr 10, 2016
Messages
26
Yes it was orange when we first checked to see if we had spark. Good idea about the filter. I'll swap it out first thing in the morning. I'm going to bring some fresh gas and dump it straight into the carb to see if that can get it to do something. Once in a while today it would belch smoke out of the carb when I'd stop cranking the motor if that means anything.
 
CaptainMak

CaptainMak

Petty Officer 1st Class
Joined
Apr 28, 2012
Messages
294
So it's definitely a carb, not a TBI unit, correct?

If ether didn't work, I'd suspect the ignition system. Orange spark means it's a weak spark. It should be blue or even whitish/blue. Pull the plugs and let us know if they're soaked in fuel. I'd suspect they will be. What kind of ignition do you have on it?
 
Scott06

Scott06

Admiral
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Apr 20, 2014
Messages
6,981
If starter fluid didn't light then check the coil primary resistance should be .6-.8 ohms, secondary resistance 9400-11700 ohms. If that is ok then go though trouble shooting the ignition module and sender in distributor. I assume you have a Thundebolt V , but could be EST, either way figure out what you have and google trouble shooting it. I don't have a portable document but have seen good step by step Tbolt V troubke shooting guides to diagnos the module and sender
 
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