25hp Johnson Needle Valve Adjustment

[lundwc16]

I have a 1977 25hp Johnson, Mod#25E77S, that doesn't want to settle into a smooth idle. Before I dig deeper, what is the starting point for the needle valve adjustment. On this carb. the needle valve is on the front of the carb above the fuel bowl.
John

 

[stinkfoot]

Have had too many beers to look now but will check my Clymer manual tomorrow and post for you. I photographed 4 pages last time and it seems to reproduce readably. PM me your email or I can post in this thread.

 

[Johnny]

John, I had a 1979 25hp Johnson and the OMC rule of thumb
is to bottom the stem out firmly but gently, then back up
1 and 1/2 turns and fine tune it from there after the motor warms up.
have you checked the needle point to ensure it is not just worn out?
are you running 50:1 gas/oil mix or something else.
Do you have a manual for that motor ??
I found the parts manual and shop service manual on ebay for about $10 each.
I am FAR from being any kind of mechanic, but the manuals sure do help.

https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1977&hp=25&model=25E77S&manufacturer=Johnson&section=Carburetor
part numbers 29, 35 and 33 are usually the culprit.
very easy to replace and not so expensive.


This is a post from iboats:

Re: 1976 johnson 25HP low speed idle carb adjustment
Initial setting is: Slow speed = seat gently, then open 1-1/4 turns.
Start engine and set the rpms to where it just stays running. In segments of 1/8 turns,
start to turn the S/S needle valve in. Wait a few seconds for the engine to respond.
As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.
Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire).
At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.



.

 

[lundwc16]

I'll take a close look at the needle valve, & try & determine if it looks worn, I did not think of that. I suspected that the starting point was 1 1/4 or 1 1/2 a turn out, thanks for the reply. I have ordered from MarinEngine in the past. I guess if I simple adjustment doesn't work ( as I know in the reality part of my brain it won't ) I'll just order a carb kit. I have a 2015, 30hp E Tec on another boat, but I just love these older outboards. I am running 50:1 in the 25 Johnson.
John

 

[stinkfoot]

The book says 1 full turn.

 

[lundwc16]

All close enough for a starting point. Thank you for the response.
John

 

[Johnny]

John - when you get ready to adjust the idle,
count how many turns it takes to bottom out
from where it is now.
if it is 1-1/4 - 1-1/2 turns, take a look at the needle points and seats.
I'm just curious as to the present setting.

 

[lundwc16]

John - when you get ready to adjust the idle,
count how many turns it takes to bottom out
from where it is now.
if it is 1-1/4 - 1-1/2 turns, take a look at the needle points and seats.
I'm just curious as to the present setting.

Will do. I'm currently in Sebastian Fla with this boat & motor, & it's 41 degrees & blowing a steady 25 so I don't know if I'll get to it for a few days,
John

 

[Johnny]

LOL oh yeah - it was a RAW day in Florida yesterday !!!!
looking forward to your boating/fishing report when you get back.
I have been to the Inlet several times but never took the boat. (pier, jetty and surf fishing).
That is on my bucket list for this year for sure.
Hope the weather improves enough for you to get out and about.

 

[lundwc16]

John - when you get ready to adjust the idle,
count how many turns it takes to bottom out
from where it is now.
if it is 1-1/4 - 1-1/2 turns, take a look at the needle points and seats.
I'm just curious as to the present setting.

Got back to it yesterday, took 1 1/2 turns to bottom out, turned it down to a little less than 1 1/4 & it ran better, BUT the needle valve just didn't "feel" right. After running the boat for a short while, it began to run rough again. I went back to the needle valve & it was more than 1 1/2 turns to bottom. A closer look revealed that the needle valve retainer, a small keyed washer the needle valve goes through, was broken. This allowed the needle to vibrate, & loose adjustment. We were able to find a replacement, & the old 25 seems to be back on track for now,
John