1968 Mercury 9.8

[mmonti]

I just pulled my boat out of the garage after sitting a few years, cleaned everything, new gas, replaced some cracked wiring, replaced the impeller and all the lower end seals. Motor fired up and is running. I cleaned the carb as best as I could but it has a rough idle, I was messing with the idle adjustment and forgot where it was set, now when I put it into gear it will bog down and die! Ooops. Was at least running in gear prior, the idle is still a little rough as well.

Ive searched and searched but cant find any info on the idle screw adjustment. How far out should it be set? What will get me in the right range to fine tune it? Could it be the high speed jet adjustment?

Thanks for the help!

Mike

 

[mrteeman]

Re: 1968 Mercury 9.8

Turn carefully in until it won't turn anymore. Turn it 1 1/2 turns out as a start position.

when warmed up and in forward turn, screw counterclockwise until rpm start's to increase, this is you point a (rich), then turn if further counterclockwise until engine starts to drop rpm, being point b ( lean)
then position the screw halway between point and point b.

I just pulled my boat out of the garage after sitting a few years, cleaned everything, new gas, replaced some cracked wiring, replaced the impeller and all the lower end seals. Motor fired up and is running. I cleaned the carb as best as I could but it has a rough idle, I was messing with the idle adjustment and forgot where it was set, now when I put it into gear it will bog down and die! Ooops. Was at least running in gear prior, the idle is still a little rough as well.

Ive searched and searched but cant find any info on the idle screw adjustment. How far out should it be set? What will get me in the right range to fine tune it? Could it be the high speed jet adjustment?

Thanks for the help!

Mike

 

[mmonti]

Re: 1968 Mercury 9.8

Turn carefully in until it won't turn anymore. Turn it 1 1/2 turns out as a start position.

when warmed up and in forward turn, screw counterclockwise until rpm start's to increase, this is you point a (rich), then turn if further counterclockwise until engine starts to drop rpm, being point b ( lean)
then position the screw halway between point and point b.

Thanks for the help, I've been waiing all night for a reply. I will adjust it when I get home this afternoon and report back.

 

[mmonti]

Re: 1968 Mercury 9.8

That looks like it did it!, I think I'm actually out closer to 1.75 turns. Its idling behind me as I type this. Its sounding good, and it doesn't die when dropped into gear now.

Now to just burn thru this gallon of gas, I mixed it at about 30:1 to make sure everything is all nicely lubed up, its been sitting awhile!

Thanks for the help!

Mike

 

[Texasmark]

Re: 1968 Mercury 9.8

That looks like it did it!, I think I'm actually out closer to 1.75 turns. Its idling behind me as I type this. Its sounding good, and it doesn't die when dropped into gear now.

Now to just burn thru this gallon of gas, I mixed it at about 30:1 to make sure everything is all nicely lubed up, its been sitting awhile!

Thanks for the help!

Mike

Nothing wrong with 1.75. I don't know when the 50:1 was first used by Merc. Probably your '68 was designed for it.....I remember in the '65 time frame it was the norm. As soon as you run your current tank, I'd go to 1 pt to 6 gallons or I guess you have the 3 gallon tank for that engine so half pint.

Mark

 

[mmonti]

Re: 1968 Mercury 9.8

Nothing wrong with 1.75. I don't know when the 50:1 was first used by Merc. Probably your '68 was designed for it.....I remember in the '65 time frame it was the norm. As soon as you run your current tank, I'd go to 1 pt to 6 gallons or I guess you have the 3 gallon tank for that engine so half pint.

Mark

I have the original tank for this motor and thats what I've always used, its about 3 gallons. When i was cleaning up the boat I realized there was rust in the tank. I need to pick up another tank, one of the new plastic types as thats all I see anywhere now. My prime bulb also split while I was squeezing it, its been running with the hose hanging in a small 1 gallon while I've been working on it.

Whats the ratio on the 1/2 pint to 3 gals? 25:1?

Mike

 

[Texasmark]

Re: 1968 Mercury 9.8

Whats the ratio on the 1/2 pint to 3 gals? 25:1?

Mike

No. A gallon is 128 oz x3 gal = 384/8 oz oil = 48 referred to as 50:1. A 6 gallon tank uses 16 oz making the same ratio.

Mark

 

[mmonti]

Re: 1968 Mercury 9.8

No. A gallon is 128 oz x3 gal = 384/8 oz oil = 48 referred to as 50:1. A 6 gallon tank uses 16 oz making the same ratio.

Mark

Ahh Thank You, yeah I always try and mix 50:1, 3oz per gal of gas how Ive been taught. My quicksilver 2 stroke bottle says the same 8oz per 3gal. Kinda of confusing if its 3oz per 1gal, but 8oz per 3 gal would make me think by doing the math 3x3=9 that its 1oz short per full tank?! To confusing I just follow the directions on the bottle for 50:1. 8oz for 3 gals.

Thanks for all the help, motor seems to be running fine now, just cleaned the carb filter and bowl this morning fresh gallon of gas at 50:1, New tags on the boat, its idling fine in the can full of water. I need to get this in the water for a good test run now.

Mike

 

[duke33]

Re: 1968 Mercury 9.8

I think different companies oil is different....I go with the label.

 

[mmonti]

Re: 1968 Mercury 9.8

Well after a test run on the water I realized I had no power in gear. Got back home checked everything out and I find that I have no spark to the top cylinder. I pulled the flywheel, checked the points, they look good, I re-gapped the points at .020 then swapped the coils. I put it all back together and the other cylinder lost spark. I see oldmercs has replacement coils, can I just replace the 1 bad one or do I have to do both?

Thanks
Mike

 

[Texasmark]

Re: 1968 Mercury 9.8

Depends on your pessimism. If one failed and were manufactured in the same place with the same parts one would ask, when is the other going to fail? Course nothing says that the new one will outlast the old one. Glad you found your problem.

Mark