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'1983 80hp idle speed

C

cadormat

Member
Hey everyone,
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I bought an '83 80 hp last year for my boat. It ran absolutely perfect for the first half of the season that I had it. Getting into the fall, I seemed to always have to put it on fast idle to start it. No matter what, whether it was cold, warm, whatever. Now its hard to tell because I don't have a tach but I think the rpm got a little lower as the season went on. The only thing I can think of would be if my idle stop bolt came loose and backed off? It did go through some pretty rough water. So I have two questions.
1) Does anyone know the proper idle rpm range for these motors, and
2) How do I wire in a tach and does it have to be a mercury tach or can I use anything?
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Help is much appreciated guys.
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Thanks!
 
Re: '83 80hp idle speed

Poor idling is often the first indication of " internal engine problems "-----------------The first thing to do is a compression test, nothing else.-----------------Post the results, if you like.--------------Did you install a new impeller when you got it ??
 
Re: '83 80hp idle speed

I haven't done a compression test since the issue started but there was one done when I bought it and all 4 cylinders were right in spec. Water pump housing and impeller was also new. 2 weeks ago I gutted the whole lower unit to re weld the bullet and skeg. Full re seal kit and impeller were put in then as well. I mean, it's only at very low rpm that it stalls. As soon as I even tap the gas it it goes like a bat outta hell.l The reason why I was wondering about the idle stop was becaus eearlier this week when I started it up for the first time, I noticed the bolt did not bottom out on the stop when I move the shifter into neutral. Don't know if that's normal. The throttle cable was also new when I bought it. Is it possible for it to stretch at all? If I can figure out how to use youtube I'll try posting a link of a vid when I take it out on the water. I'm going tomorrow. Thanks for the post!
 
Re: '83 80hp idle speed

OK , now I know more.---------------------I would simply adjust the idle stop to speed up the idle so it does not stall.--------------Do another compression test and use it for future info.
 
You finally posted some detailed info and history on the motor !!!!----------Outboards tachometers generally run off the charging system / alternator coils.----So factory tach is the way to go.----They often just plug into the control, but hey I have no idea what control you have !!!
 
So I had it out on the weekend. Adjusted the idle stop and it was still acting up. I figured out how to post videos so here's a couple links to them. The first one is pretty much what it does every time I go to start it. This was a cold start. It was off for about 20 minutes before I shot the video.
http://www.youtube.com/watch?v=OnQAnW2TOjg&NR=1

The second one is of the motor at full throttle.
http://www.youtube.com/watch?v=G4AjQhulUco&feature=related
I'm starting to think that it might be something as simple as the fuel pump not pulling enough vacuum. A leaking diaphragm maybe? Or the carb running lean at idle.
 
From your (nice) videos it sounds like the idle mixture is off. Try this:

1. Warm the motor thoroughly then tie the boat to a dock

2. Put her in gear and SLOWLY adjust each carb for the best idle. When it 'spits' back on you it's too lean, so open the idle screw about 1/4 turn CCW.

3. WAIT at least a minute to let the motor settle down with each new setting--that's the secret to getting it right.

4. Finally, open both idle screws another 1/8 turn CCW since a bit rich is better than a bit lean.

Jeff
 
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Thanks! Videos are so much better for explaining. Haha! Sorry about the sound quality though. It was shot with a digital camera. That would be awesome if it's just out of tune. Now you say to tie it off on a dock when it's in gear. Is that just to put it under more load or can I do the same thing if I cruise around at low speed and have someone steer?
And to start, I just turn CW a bit at a time until I hear it starve, then back it out the richen it? That sounds pretty straight forward. Thanks!
 
Correct. With the boat moing along it's near impossible to get the idle mixture correct. The are where you are doing this needs to be wake free as well.

Jeff
 
cadormat said:
So I had it out on the weekend. Adjusted the idle stop and it was still acting up. I figured out how to post videos so here's a couple links to them. The first one is pretty much what it does every time I go to start it. This was a cold start. It was off for about 20 minutes before I shot the video.

The second one is of the motor at full throttle.
I'm starting to think that it might be something as simple as the fuel pump not pulling enough vacuum. A leaking diaphragm maybe? Or the carb running lean at idle.
Click to expand...
Hi cadomat I have a mercury 80hp 4 cylinder 2 stroke
How do you get the outboard to idle nice ???
 
racerone said:
Re: '83 80hp idle speed

Poor idling is often the first indication of " internal engine problems "-----------------The first thing to do is a compression test, nothing else.-----------------Post the results, if you like.--------------Did you install a new impeller when you got it ??
Click to expand...
hi racerone I have a 80hp mercury 4 cylinder 2 stroke just would like some advice for a good idle setting
 
The picture is taken with the controller in neutral
Should this be the position on the highlighted bolt and nut ???
 

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Post the results of a compression test.-----It looks to me that someone has made adjustments in the hope of getting it to run better.----These arms and linkages rarely need adjustments during normal operation !!
 
racerone said:
Post the results of a compression test.-----It looks to me that someone has made adjustments in the hope of getting it to run better.----These arms and linkages rarely need adjustments during normal operation !!
Click to expand...
Hi racerone

I personally have not messed with the bolts and nuts
See the description below it’s how I purchased it
Says it doesn’t idle

1681315171164.png
 
Doesn't idle but it is " MINT " says a lot to me.---Your motor could be junk.-----I can't put my hands on your motor so you have to make an effort to inspect this motor.
 
Lots of motors start and run.-----But that means nothing.-----Start with posting the compression test numbers.-----Or hurry to your local friendly shop ( if you can find one ) to get this motor set-up to idle !!
 
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