# 78 25 hp Evinrude what type of oil do you use?



## Topshelf (May 24, 2005)

I have a 1978 25 hp Evinrude. The thing runs great, starts 1st or second pull, but it doesnt idle down low very good. Not really a problem since I use a elec trolling motor for slow stuff. I have been running the evinrude brand of oil at 50 to 1 for the last few tanks. When I was changing the plugs in it yesterday I noticed that the plugs seem pretty dark when I pulled the old ones. 

#1 What brand of oil do you guys use for the older outboards?

#2 Whats the normal plug look like on one of these older motors? I'm use to seeing plugs on newer 2 strokes that are much whiter in color.

#3 I have heard of guys running leaner mixtures to make them idle better but I hate to fry a piston over it. Does anyone runner leaner mixes?


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## alex-v (Mar 24, 2005)

> #2 Whats the normal plug look like on one of these older motors?


I am thinking of taking some of my pulled plugs to the dealer and asking their mechanic to take a look at them. Something you might want to think about.


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## andy capp (Aug 14, 2002)

I would say it is running rich. try 1 heat range hotter plugs and have the carb looked at. You can run by adjusting screws on th carb.


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## Topshelf (May 24, 2005)

Yesterday i took the cover off and checked out the carb. The rich / lean knob is turned all the way to lean right now. 

After looking at the evinrude oil bottle that I used the last time I for mixture rates I wonder if I had a brain fart  and mixed double the oil I should have for 6 gallons? I'm not really sure of that though because I would think that double the oil would have made it way to rich and killed the plugs?

I'm going to go out and take some pic's of the old plugs and the new ones I just ran yesterday and will post them,


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## waterfoul (May 18, 2005)

To check the plugs you MUST run the motor wide open and then shut it off without slowing down. Slowing down only darkens them up in short order. If you checked them after idling back to the ramp or running it at a low idle, or even medium idle on the hose, chances are they will be dark. No load on them, they won't burn all the fuel/oil. Take it out to the lake, run it wide open for 2 minutes, shut it off, pull a plug. Should be dark chocolate milk color... and not dripping wet. A little damp is o.k. But not wet.

I've been running Citgo 2 stroke oil the last two seasons thru my Merc 50 and the Mariner 45 with no issues. Neither motor loads up, both idle well. But, I always run 50:1 (or as close as humanly possible). No more, no less.


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## Topshelf (May 24, 2005)

waterfoul said:


> Take it out to the lake, run it wide open for 2 minutes, shut it off, pull a plug. Should be dark chocolate milk color... and not dripping wet. A little damp is o.k. But not wet.


Well now that you say that the color should be dark chocolate color maybe It's ok? Basiclly thats what they looked like. I may go get a can of seafoam and run that through it to clean the carb out a little and maybe that will help out the idle.


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## SabikiRig (May 1, 2004)

Topshelf said:


> Yesterday i took the cover off and checked out the carb. The rich / lean knob is turned all the way to lean right now.
> 
> After looking at the evinrude oil bottle that I used the last time I for mixture rates I wonder if I had a brain fart  and mixed double the oil I should have for 6 gallons? I'm not really sure of that though because I would think that double the oil would have made it way to rich and killed the plugs?
> 
> I'm going to go out and take some pic's of the old plugs and the new ones I just ran yesterday and will post them,


 
Topshelf,

If the motor ran fine before the last tank of gas you mixed it may be a good idea to change the plugs (keeping the same heat range) and leave the Carb/Adjustments alone.

I believe that motor requires 50:1, I know my 1999 and 2001 25 Johnson's do. Running double the oil would cause some issues that you describe.

Should you forget the mix ratios here is a quick easy way to calculate them: 

Gallons of Gas x 128 divided by 50 = the amount of oil.

ie: 5.25x128/50=13.44 ounces of oil

My cell phone has a calculator so figuring our the ratios is simple should I forget the premixing bottle I bought at Meijers.


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## FishTales (Feb 13, 2002)

Here you go fella's, click on the link and add to your favorites. Rich

Gas to Oil Calculator


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## waterfoul (May 18, 2005)

For 50:1 just figure 2.6 ounces of oil to every gallon of gas. Easy as that.


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## SabikiRig (May 1, 2004)

waterfoul said:


> For 50:1 just figure 2.6 ounces of oil to every gallon of gas. Easy as that.


 
That works well too.....


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## Topshelf (May 24, 2005)

Well I can see a pretty big difference from the old to the new plugs but both still look pretty rich to me?

old plugs







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New plugs with about +/- 3 hours on them









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## Natlight (Feb 6, 2004)

Topshelf said:


> I may go get a can of seafoam and run that through it to clean the carb out a little and maybe that will help out the idle.



I have a 1980 50 horse johnson. Bought her last year, always stalling at times when I was throttled down and idleing. This year I changed the plugs and have ran a seafoam in all of the gas tanks. Huge difference. Now I can troll with her and idle and she never sputters out anymore. I'm a believer in the stuff.


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## KS up north (Jan 2, 2004)

I have a '78 evinrude 15 hp, I run 40:1 and stock plugs, can idle and troll all day long, although I have an external rich/lean (idle) control knob and need to adjust it ("leaner") when running at idle, in neutral.
I have a few questions......
How old were the "old" plugs?
Are the spark plugs the correct ones? (I have owned several "used" boat motors, dirtbikes, snowmachines, etc... and always look up the correct plugs, cant just get the ones that were in it before, who knows if they were correct???) 
Have you ever checked the spark plug wires? They are often overlooked!


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## Topshelf (May 24, 2005)

KS up north said:


> I have a '78 evinrude 15 hp, I run 40:1 and stock plugs, can idle and troll all day long, although I have an external rich/lean (idle) control knob and need to adjust it ("leaner") when running at idle, in neutral.
> I have a few questions......
> How old were the "old" plugs?
> Are the spark plugs the correct ones? (I have owned several "used" boat motors, dirtbikes, snowmachines, etc... and always look up the correct plugs, cant just get the ones that were in it before, who knows if they were correct???)
> Have you ever checked the spark plug wires? They are often overlooked!


The old plugs were put in in the spring. Somewhere around Late march early April.

As far as mixture goes I run 50:1 which is what the specs call for. 

Funny you should mention the plug model. I was reading another forum and found a link to a chart for plugs / engines. Turns out the ones that were in it were not the correct model according to the chart. I myself had bought them new and just replaced the old ones with what was in it. I bought the motor last fall and only put a few hours on it before storing for the winter. 
The Plug wires look fine. no cracks or checking on the rubber. I really do think that the new plugs run better and with a little seafoam in a fresh tank of fuel it may clean those Carb jets out where it will idle better. Its a 25 so don't really expect it to idle like a 10 hp kicker, but it should idle better than it does.


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## bigair (Apr 16, 2004)

Topshelf said:


> Yesterday i took the cover off and checked out the carb. The rich / lean knob is turned all the way to lean right now.
> 
> After looking at the evinrude oil bottle that I used the last time I for mixture rates I wonder if I had a brain fart  and mixed double the oil I should have for 6 gallons? I'm not really sure of that though because I would think that double the oil would have made it way to rich and killed the plugs?
> 
> I'm going to go out and take some pic's of the old plugs and the new ones I just ran yesterday and will post them,


 By "all the way lean do you mean screwed all the way in. If that is the case something isn't right. Possibly the needle or seat are damaged. If it doesn't idle down low well, what are the symptoms. Hiccups and misfires = TOO LEAN IN THE IDLE CIRCUIT. The high speed is fixed on that motor and can't be adjusted.


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## Flash (Jan 17, 2006)

QuickSilver for my 1973 Merc 402 (40hp 2 stroke). No problems idling down. Can troll at nearly 1.8mph according to my GPS.


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## Topshelf (May 24, 2005)

bigair said:


> By "all the way lean do you mean screwed all the way in. If that is the case something isn't right. Possibly the needle or seat are damaged. If it doesn't idle down low well, what are the symptoms. Hiccups and misfires = TOO LEAN IN THE IDLE CIRCUIT. The high speed is fixed on that motor and can't be adjusted.


The air mixture screw comes out of the front of the air box and has a indicator on it. Its adjusted all the way to the lean side. 
:0 My bad, good thing I'm not a mechanic as I would go broke. After taking this pic I realized that the scew will go leaner. I thought it had a stop on it and was as far as it would go lean. 








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Symptoms are once its idling down to a crawl it will miss every once in a while for about a minute or so and then just die. I wonder if I just need to adjust the idle speed screw on the Tiller handle to a little higher of a RPM? Is that possible

As an update I ran it with fresh gas and the new plugs on Monday and it ran great. The Idle was a little better than normal but I really didnt try to troll or anything with it? I really only slow to a crawl usually at the ramp.


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## bigair (Apr 16, 2004)

I going to bet the missing you are experiencing is a lean hiccup and your idle screw needs to turned out to eliminate it.


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