Reply
 
Thread Tools Search this Thread
 
Old 03 May 2015, 09:52   #1
Member
 
Country: UK - England
Town: Bournemouth
Make: Avon
Length: 3m +
Engine: Merc 25hp 2stroke
Join Date: Nov 2014
Posts: 93
Adjusting idle 25hp Merc 2st

I recently had the carb stripped and cleaned on my 1993 merc 2 stroke, it runs fine now but the idle is really high and I have no idea of how to adjust it?

I figured there must be a screw adjustment somewhere but cant see one?
Attached Thumbnails
Click image for larger version

Name:	5E965A71-C3FE-4EB1-9BC4-44199A22421A_zpsqj1aw1rl.jpg
Views:	89
Size:	146.3 KB
ID:	105015  
__________________

__________________
mattwarner is offline   Reply With Quote
Old 03 May 2015, 14:27   #2
Member
 
The Gurnard's Avatar
 
Country: UK - Scotland
Town: Stirling
Boat name: The Gurnard
Make: Quicksilver
Length: 4m +
Engine: mariner 25hp 2s
Join Date: Jul 2013
Posts: 986
I think there could be an access plug on the side just off the right of your photo..it should be under the plug..if its the same model Im thinking ?

Here is the complete service manual for the mercury 20-25hp engines..and I have opened it at the page covering the idle adjustment screw

Boatinfo - Mercury Service Manual for 20jet-20-25hp

hope that helps..there are some differences in models ..but its hopefully there

Or turn to page 102 which give a bit of detail on setting the idle mixture screw etc. Im no expert though..I just read the manual for the bits I do on my mariner 25Hp engine
__________________

__________________
The Gurnard is offline   Reply With Quote
Old 04 May 2015, 03:40   #3
Member
 
Country: UK - England
Town: Bournemouth
Make: Avon
Length: 3m +
Engine: Merc 25hp 2stroke
Join Date: Nov 2014
Posts: 93
thanks for this, ive looked through all the models but mine has a different set up and there isn't an idle adjustment where the manual shows?
__________________
mattwarner is offline   Reply With Quote
Old 04 May 2015, 04:05   #4
Member
 
The Gurnard's Avatar
 
Country: UK - Scotland
Town: Stirling
Boat name: The Gurnard
Make: Quicksilver
Length: 4m +
Engine: mariner 25hp 2s
Join Date: Jul 2013
Posts: 986
I guess that is the problem with so many different models over the years Matt..it is certainly in that position on my 2006 outboard. Took this photo 5 mins ago..and the cap is removed..screwdriver is on the adjustment screw..through hole in the plastic plate




Perhaps someone else will know..as mentioned..Im no expert and just work through the service repair manual in the link to get my issues sorted
Cheers
__________________
The Gurnard is offline   Reply With Quote
Old 04 May 2015, 04:15   #5
Member
 
The Gurnard's Avatar
 
Country: UK - Scotland
Town: Stirling
Boat name: The Gurnard
Make: Quicksilver
Length: 4m +
Engine: mariner 25hp 2s
Join Date: Jul 2013
Posts: 986
Perhaps just the plastic plate is removed on your version Matt..your carb looks same as mine ? Is there a screw at the red arrow on your photo.. I would have though it would be around the same location ?



If not..I cant help..im on thin ice as it is..as I have never had to touch mine
__________________
The Gurnard is offline   Reply With Quote
Old 04 May 2015, 05:12   #6
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Suzuki DF20 EFI
Join Date: Nov 2007
Posts: 3,276
Gurnard. The screw you're showing is the idle mixture which of course will affect idle speed when it's turned but I think Matt is looking for adjustment of the base idle speed. Your setup is the same as on my Mercury 15 Gurnard and the idle speed screw is on the left of the carb (as referenced in your pic) and just behind the fuel pump. It is a cam type thing with a brass headed screw with a spring round it.

"a" in this diagram...

http://ww2.justanswer.com/uploads/ol...6_mercidle.jpg

But of course Matt's is missing that whole assy. There were some models where the idle was factory set from new and there was no variation possible... the manual refers to this possibility. The other thing is unlike ours Matt's is on remotes. Is it possible there is some adjustment of idle speed possible at the remote levers? Does it have a fast idle facility at the remote end.

I wonder if the throttle remote lever or cable assy isn't allowing the throttle at the carb end to fully return to the idle posn.
__________________
Fenlander is offline   Reply With Quote
Old 04 May 2015, 05:13   #7
Member
 
Country: UK - England
Town: Bournemouth
Make: Avon
Length: 3m +
Engine: Merc 25hp 2stroke
Join Date: Nov 2014
Posts: 93
Yes there's a screw same place, I thought that was the mixture adjustment screw? Is that the same thing?
__________________
mattwarner is offline   Reply With Quote
Old 04 May 2015, 05:40   #8
Member
 
The Gurnard's Avatar
 
Country: UK - Scotland
Town: Stirling
Boat name: The Gurnard
Make: Quicksilver
Length: 4m +
Engine: mariner 25hp 2s
Join Date: Jul 2013
Posts: 986
I again...i thought it was the idle mixture screw you were looking for.. but now i re read the thread ..I realise its not what you want..its still all in the service manual though..try this page. Its easly for me to find as I have a real paper copy

Boatinfo - Mercury Service Manual for 20jet-20-25hp

and as Fenlander correctly mentions..some are factory set and dont have a idle screw.

matt the screw I referred to adjust the lean / rich mixture..if your outboard is running fine..dont touch it..but it tells how to adjust it if you need too

sorry for confusing the issue
__________________
The Gurnard is offline   Reply With Quote
Old 04 May 2015, 06:52   #9
Member
 
Country: UK - England
Town: bicester
Length: no boat
Engine: outboard only
Join Date: Feb 2009
Posts: 894
on the front of the outboard, is the big plastic knob turned as far left as it will go? If not it should be, for normal running, it is only supposed/ idealaly to be used for the intial start up. Idle air screw one and a half turns out from lightly seated, regardless of what the service manual has printed in it.Some are set by the timing for which you need a strobe light and a rev counter.
__________________
uncle al is offline   Reply With Quote
Old 04 May 2015, 08:09   #10
Member
 
Country: UK - England
Town: Bournemouth
Make: Avon
Length: 3m +
Engine: Merc 25hp 2stroke
Join Date: Nov 2014
Posts: 93
Thanks for the replies, the idle knob is definitely turned back all the way and remotes are not the issue, it seems the throttle arm on he carb is back as far as it will go and there is no adjustment.

I know when the carb was rebuilt the idle mixture was turned out 2 full turns from lightly seated which is how he found IT, if I lean it off half a turn will it drop the revs down?
__________________

__________________
mattwarner is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 03:33.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.