Falls back to idle at wot

Covemaster2019

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May 3, 2019
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2
115 mercury 4s dies back to idle after running wotbfor 1-2 minutes then picks back up to 5700 rpm wot and repeats
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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47,306
Welcome aboard

Most likely fuel system related. When was the last time the carbs were serviced?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
47,306
The issue is still fuel system related

Since there are many variations of the 115 and you didnt specify

To help us help you, post your serial numbers and year

Do the basic trouble shooting per the manual
 

alldodge

Moderator
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Mar 8, 2009
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First thought is fuel pump is not keeping up. I would look at a fuel line restriction or the low pressure lift pump
 

GA_Boater

Honorary Moderator Emeritus
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May 24, 2011
Messages
49,038
Welcome aboard, Cove.

We do need more info about the motor. Having the serial number helps a lot.

When this happens, the throttle is wide open and the motor cycles from WOT to idle until you chop the throttle. What happens at other throttle settings? Say running at mid-throttle or 3/4's, does the motor eventually fall over to idle?

I would eliminate the external fuel system by using a portable tank with it's hose. If it runs OK, you know it's the motor.
 
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