starting problem with 3.0 mercruiser

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Fscott4

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I just installed a new carb on my 91 3.0 mercruiser. its an aftermarket but I dont think that is the issue. When I turn the key to start the engine it will fire right up and when I release the key it dies. If I increase the throttle and turn the key it will start on the corresponding increased rpm of the throttle, but again when I release the key back to the run position the engine dies. If I hold the key in the start position the engine will run fine until I release the key to the start position.
I was having carb issues with the original and just went with the aftermarket which seems to be functioning fine. This seems to be pointing towards electrical but I am at a loss as to where to even start looking. Any help or direction on this will be greatly appreciated.
Thanks!!!!
 
Scott Danforth

Scott Danforth

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Fscott4 said:
I just installed a new carb on my 91 3.0 mercruiser. its an aftermarket but I dont think that is the issue.
Click to expand...
where did you get the aftermarket carb?

if you got it from Amazon or ebay, it may be a problem.

however your key switch needs replacing.
 
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Fscott4

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How can I verify the switch is bad? I will defintely replace it but I would like to rule that out for certain.
 
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Fscott4

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I dont think it was doing this at all before the carb change.
 
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Fscott4

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OK, I will pull it out and wire it. This just feels electrical to me...
 
Scott Danforth

Scott Danforth

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Volt meter on the purple wire . Key on, should have battery voltage.
 
flashback

flashback

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I have an old fluke and it's still reading but the others have gotten neglected..
 
Scott06

Scott06

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Fscott4 said:
I just installed a new carb on my 91 3.0 mercruiser. its an aftermarket but I dont think that is the issue. When I turn the key to start the engine it will fire right up and when I release the key it dies. If I increase the throttle and turn the key it will start on the corresponding increased rpm of the throttle, but again when I release the key back to the run position the engine dies. If I hold the key in the start position the engine will run fine until I release the key to the start position.
I was having carb issues with the original and just went with the aftermarket which seems to be functioning fine. This seems to be pointing towards electrical but I am at a loss as to where to even start looking. Any help or direction on this will be greatly appreciated.
Thanks!!!!
Click to expand...
So you have a man overboard or kill switch ? That is exactly what happens when mine gets tripped
 
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Fscott4

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Well it seems that these engines run much better with the cut-off tether installed. Holy crap what a dope I am! I saw that when I was looking at the ignition switch. It runs great now. Now I add that to the pre-start list...
 
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Fscott4

Petty Officer 3rd Class
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Scott06 said:
Same happened to me out on the water... got my daughter who was out on the jetski to tow me in… no spark figured it out quick but funny get towed in by your 15 yr old…
Click to expand...
Hopefully she will be bringing that up for years to come!
 
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