69 mercury 9.8 dies after 5-10 seconds

d&Jboat

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Jul 1, 2006
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My dad and I have been messing with out 69 mercury 9.8 weve replaced fuel pump, spark, and water pump, and finally got it running, however it dies after 5-10 seconds regardless of whether it is in idle or full throttle. It sounds to me like it is just starving of fuel and we dont know where to start, maybe the carburetor? Thank you for your help.
John
 

G.I. Jim

Cadet
Joined
Mar 15, 2010
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27
Re: 69 mercury 9.8 dies after 5-10 seconds

I'm having the same problem, same motor did you ever figure it out?
 

Iceman66

Petty Officer 2nd Class
Joined
Jun 30, 2008
Messages
199
Re: 69 mercury 9.8 dies after 5-10 seconds

My dad and I have been messing with out 69 mercury 9.8 weve replaced fuel pump, spark, and water pump, and finally got it running, however it dies after 5-10 seconds regardless of whether it is in idle or full throttle. It sounds to me like it is just starving of fuel and we dont know where to start, maybe the carburetor? Thank you for your help.
John



A carb cleaning will do the "trick" I guess.
 

Mi duckdown

Commander
Joined
Apr 14, 2007
Messages
2,575
Re: 69 mercury 9.8 dies after 5-10 seconds

Buy a carb kit with new float and rebuild.
 
Joined
May 13, 2013
Messages
11
Re: 69 mercury 9.8 dies after 5-10 seconds

Could be the exact opposite. Id change the plug. If the plug isn't firing right it could be flooding it. Also, I am not extremely familiar and may get laughed at, try cleaning the "breather" or making sure it is non restricted.
 

ddwilson

Petty Officer 2nd Class
Joined
Apr 8, 2012
Messages
116
Re: 69 mercury 9.8 dies after 5-10 seconds

I would try cleaning and rebuilding the carb first, if the fuel pump is new that should not be the problem. It sounds like a fuel problem to me.
 

G.I. Jim

Cadet
Joined
Mar 15, 2010
Messages
27
Re: 69 mercury 9.8 dies after 5-10 seconds

Spark is good, I can get it running for 1-3 seconds on starting fluid. I'm gonna pick up a carb rebuild kit tomorrow and see if that does the trick.
 

G.I. Jim

Cadet
Joined
Mar 15, 2010
Messages
27
Re: 69 mercury 9.8 dies after 5-10 seconds

Wasn't able to find a rebuild kit so I tore the carburetor apart and gave it a good cleaning blowing carb cleaner through everything. I was able to salvage all the gaskets so everything went back together nicely. Unfortunatly i am still having he exact same problem. Any ideas?
 
Joined
May 13, 2013
Messages
11
Re: 69 mercury 9.8 dies after 5-10 seconds

Is there any obstructions on the breather? If your spring isn't working it could allow the choke to engage.
 

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Re: 69 mercury 9.8 dies after 5-10 seconds

Is there any obstructions on the breather? If your spring isn't working it could allow the choke to engage.

No "breather" on this motor.

You've got fire and (apparently) compression, so it would appear you've got a fuel delivery problem.

You say you replaced fuel pump, but not what you replaced it with. New? Rebuilt? Used? Do a fuel pump check by removing the cap off the top of the carb, move it to the side over a coffee can, and spin the motor over as best you can without the recoil (a 1/2" rope with a knot in the end should give you a grip on the flywheel cogs.) Note how much, if any fuel is pumped into the can.

Check the float height. Invert the carb cap. Should look like this if set up correctly.
 

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Mi duckdown

Commander
Joined
Apr 14, 2007
Messages
2,575
Re: 69 mercury 9.8 dies after 5-10 seconds

There are carb Kits out there. Why any person would open a carb and not rebuild it is beyond ME. .???
 

G.I. Jim

Cadet
Joined
Mar 15, 2010
Messages
27
Re: 69 mercury 9.8 dies after 5-10 seconds

I think I'm just gonna send it to the shop, I don't really have the time to keep messing with it. I'll post the solution when it is found, thanks for the help everyone.
 
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