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 Post subject: 1987 Evinrude 25hp 2 cyl
PostPosted: 29 Jul 2016, 15:43 

Joined: 21 Jan 2014, 20:39
Posts: 44
Location: Fort Pierce, Florida
I've got a '87 Evinrude 25hp.

This thing has been a battle since day one. Started with headgasket, exhaust cover gasket, primer solenoid rebuild, carb clean, then carb rebuild.

Now I've finally got it to were it will run great PAST 1/8th throttle, but it will not idle worth 2 pennies, nor does it want to start without fast idle lever wide open, then I have to quickly shut fast idle lever and slam her into gear. Then it runs fine. Will troll in gear at 1/8th of throttle no problem. No hiccups at high rpm whatsoever.

I've got the timing set correctly and slow speed jet set at 1 1/2 out. Could this be a weak fuel pump problem?

Carb was completely cleaned and rebuilt. Float is set parallel with gasket surface, all orifices cleaned out, etc etc. New fuel lines, new primer..

Thanks,
Adam.


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 Post subject: 1987 Evinrude 25hp 2 cyl
PostPosted: 29 Jul 2016, 17:44 
Donor
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Joined: 15 May 2010, 00:38
Posts: 2396
Location: Central Florida
To pop both the exhaust cover and the head gasket the engine had to be pretty darned hot.
Not that it will affect slow speed running but you made no mention of replacing the rubber deflectors in the block. Those will have melted and deformed and can and will restrict water flow until replaced. Do not tell me they were okay...not if the head gasket was blown. They are not.
No, it will not be a fuel pump. A pump that will supply fuel at WOT will supply fuel easily at idle. A simple check of the fuel pump is to hand pump the primer bulb and see if it makes a difference.
You may need to lean the needle some at idle and try that but from what you are describing I am thinking something else.
Now....lets start with the basics.
What is your compression?


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 Post subject: 1987 Evinrude 25hp 2 cyl
PostPosted: 30 Jul 2016, 09:59 

Joined: 21 Jan 2014, 20:39
Posts: 44
Location: Fort Pierce, Florida
Im not 100% sure the headgasket was blown, I was getting water intrusion on cylinder #1, so because of the easy replacement of the heagasket i just went and did it. Before headgasket replacement compression was 110/112. After it was 112/115. Exhaust cover gasket was the next place i checked for a water leak and the gasket did look blown out, so I believe thats where my water was coming from. Compression still sits around 112/115 (top/bottom respectively).

Pumping the primer bulb at idle does nothing. Both coils and stator ohm out to spec and both coils will jump a 7/16 gap with a nice spark. This thing runs flawless at anything above 1/8th of throttle. It just doesnt want to idle worth a dang.


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 Post subject: 1987 Evinrude 25hp 2 cyl
PostPosted: 30 Jul 2016, 17:55 
Donor
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Joined: 15 May 2010, 00:38
Posts: 2396
Location: Central Florida
Then let's try the simple things first. Go with the low speed adjustment.
When started and warm adjust the low speed clockwise to the highest idle and just a bit beyond, until the engine begins to sag in RPM or spits lean.
Do this in small increments and wait several seconds between adjustments. Add adjustments should be made in the water as this will give the engine the back pressure it needs while making an adjustment.
When the engine does one or the other then back the adjustment needle back out around 1/4 turn. This will get you in the ball park. Small adjustments can be made from this initial adjustment.


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PostPosted: 11 Aug 2016, 22:22 

Joined: 07 Aug 2016, 09:40
Posts: 1
I have an 1984 Johnson 25 hp. I notcied changing the plugs made a major difference at idle. Surface gap plugs work best for WOT. I put in champion ql77jc4 what a difference.

Sent from my SM-G935V using Tapatalk


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