Mercury 2.5 HP 4 Stroke idles but won't accelerate

Status
Not open for further replies.

MikeMcCallie

Recruit
Joined
Mar 29, 2013
Messages
2
I tried to go out on my boat this week and my 2.5 hp Mercury 4 Stroke would idle but will not accelerate. I cleaned the fuel tank, totally disassembled the carburetor, checked the inline filter and it still will not accelerate. At full acceleration its runs the same as if it were idling. Any ideas?
 
Last edited:

FishinDave

Seaman Apprentice
Joined
Jun 12, 2012
Messages
46
Re: Mercury 2.5 HP 4 Stroke idles but won't accelerate

Your throttle valve may not be opening. Check to see if your throttle lines are attached to your carb and your choke valve and your throttle valve are opening.
 

MikeMcCallie

Recruit
Joined
Mar 29, 2013
Messages
2
Re: Mercury 2.5 HP 4 Stroke idles but won't accelerate

Your throttle valve may not be opening. Check to see if your throttle lines are attached to your carb and your choke valve and your throttle valve are opening.

Throttle is opening. I have tried to adjust the float to parallel to the carb body. It is smoking. When I go to remove the bowl it has fuel in it. When the motor is idling I can blow air into the into the carb and it will accelerate. Any suggestions?
 

raczekp1

Lieutenant
Joined
Mar 30, 2010
Messages
1,327
Re: Mercury 2.5 HP 4 Stroke idles but won't accelerate

what about chocke leaver, is it workng or you accelerate no choke on all the time,
what about prob, did you heat something under water?maybe prop is turning on hub?
 

micahm

Recruit
Joined
May 2, 2013
Messages
2
Re: Mercury 2.5 HP 4 Stroke idles but won't accelerate

Any luck with this problem? I am having the same problem with no relief. I have cleaned and cleared every part of the carb. Checked the plug, replaced gas and even tried talking nicely to it. It starts on the first pull and runs great in idle. When I rev it up it initially revs then settles back down to idle and just tends to have more exhaust. Oil and everything seem to be in order with not leaks anywhere. Any help would be appreciated.

Micah
 

Bosunsmate

Admiral
Joined
Apr 7, 2012
Messages
6,129
Re: Mercury 2.5 HP 4 Stroke idles but won't accelerate

Pull the fuel line at the carb and check it is flowing freely.
 

micahm

Recruit
Joined
May 2, 2013
Messages
2
Re: Mercury 2.5 HP 4 Stroke idles but won't accelerate

cleaned all the lines. cleaned the fuel filter and still no change.
 

eddyh

Recruit
Joined
May 10, 2013
Messages
2
Re: Mercury 2.5 HP 4 Stroke idles but won't accelerate

Having same problem with my 25hp. I've seen it before. The CDI's get wet and need to be replaced. I think that's the name for them, something like capacitive discharge ignition, not sure. If you leave the motor out and these suckers get damp they short and then are shot. You get some spark, enough for idle but when you throttle up she floods out. Pull my plugs and they are wet. A dealer can test them to be sure. It's not cheap to replace. That's were I'm headed next.

Ed Hetzel
 

jelake

Recruit
Joined
May 15, 2014
Messages
4
Re: Mercury 2.5 HP 4 Stroke idles but won't accelerate

I just bought a used 2.5HP model from 2012 and I'm having the same issue. Starts fine but won't accelerate past idle. It runs very slightly faster and a lot rougher.

Have you guys found a solution to this?
 

stewieandbabs

Recruit
Joined
May 16, 2015
Messages
1
Did you come up with an answer to ( won't accelerate past idle ) I have one same problem , only will rev up if I blow air into the carb.Acts like no manifold vacuum.
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
Please start a new topic with your problem. This one is dead as a doornail. Look at the tips on top of the page.
 

eddyh

Recruit
Joined
May 10, 2013
Messages
2
I pulled and cleaned the carb, jets were plugged. New plastic gas can too ( old one rusting).
 
Status
Not open for further replies.
Top