Merc 9.9 Throttles Down to 1/2 From WOT

bucky4

Seaman Apprentice
Joined
Jul 29, 2002
Messages
36
I'm posting this for a friend. He has a 9.9 Merc, about 10-12 years old, that will die down to about 1/2 throttle from the wide open position. He must bring the motor back to idle and then start again. The problem is intermittent and can happen on the first throttle up of the day or the last one, but it usually occurs at least once during each time out. <br /><br />This started last year, so he had a certified Merc mechanic replace everything in the fuel <br />system with new components - carb (not rebuild), tank (plastic type), filter, etc., etc. In addition, he did a complete check of the motor and did a tune up too. <br /><br />It ran great for a few times out last year and now this year, it started again. Any ideas what could be wrong? <br /><br />Thanks,<br />Jim
 

DHPMARINE

Captain
Joined
Dec 16, 2003
Messages
3,688
Re: Merc 9.9 Throttles Down to 1/2 From WOT

I probably don't have the answer,but I've seen this on 9.9s that troll alot.The exhaust tube under the powerhead gets clogged with carbon,and can't let the exhaust out.No distinct symptoms,we just pull the powerhead and look,as a last resort.<br /><br />DHP<br /><br />Happens alot on pontoon boats.
 

bucky4

Seaman Apprentice
Joined
Jul 29, 2002
Messages
36
Re: Merc 9.9 Throttles Down to 1/2 From WOT

Thanks DHPMarine for the reply. I'll tell him to get it checked. <br /><br /><br />Anyone else have an opinion?
 
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