'68 Mercury 110 9.8hp

XTRME 94

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This motor has me puzzled. My Dad bought a Jon Boat with this engine and I've been trying to help him rebuild it. Replaced the worn pistion rings, sealed the case, got it running decently at idle. When we tore it down, it was obvious that one of the coils had been replaced, points and condensers had been done. We replaced the wires, added new plugs, changed the fuel filter. Now the dilima:

In a tank, with no load on the motor, it seems to run fine. It ALWAYS starts. Very predictable. Choke it, and pull till it sounds like it'll start. Un-choke it and it'll start on the 2nd pull, just like clock-work. Let it warm up, and drop it in gear. In a tank it will run all day. Accellerate no problem. Foward or in Reverse.

Take it to the lake and it's a different story. Starts and idles fine, but when you drop it into gear, if it has a LOAD on it, it will come off idle, but it has NO POWER and if you try and accellerate, it's like there isn't anything there, and then it will start mis-firing. It only does it under load.

My I thought the obvious problem was a weak coil (since 1 had been replaced, and the other was the original). Purchased a new one and while it does idle better, it didn't solve the accelleration issue. It's not an issue of the handle not turning or opening up the carb, and "I" don't believe it's a fuel issue, or it would do the same thing when it wasn't under a load wouldn't it?

Anyone have any ideas?
 

XTRME 94

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Re: '68 Mercury 110 9.8hp

Also, can anyone tell me, if you are looking at the motor from the front (carb side) you would then have a coil left of the carb and right of the carb, which spark plug are those wires suppose to go too? ie left coil to top spark plug, right coil to bottom spark plug.............or vice versa? If I remember correctly, we have the right to the top and the left to the bottom................but then that's the way it was when he bought it.........
 

jerryjerry05

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Re: '68 Mercury 110 9.8hp

If it dies when you give it a load.You check the fuel pump?
What's the compression?You sure there is spark on both cylinders?
Clean the carb and rebuild the fuel pump.Vent open on the tank.No water in the fuel?
 

XTRME 94

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Re: '68 Mercury 110 9.8hp

If it dies when you give it a load.You check the fuel pump?
What's the compression?You sure there is spark on both cylinders?
Clean the carb and rebuild the fuel pump.Vent open on the tank.No water in the fuel?


I don't believe he's checked the fuel pump as it appears to be getting fuel, it just won't accellerate under load.

Compression was only 60psi before the ring change, it was 125psi after I believe.

Before we replaced the coil we had a blue/white spark at one of the spark plugs and a yellowish one at the other. After changing the coil, we got a blue/white spark on all the plugs.

Carb is clean, may need to be rebuilt.........

New tank and new fuel, so I don't think that's the issue.

Thanks for the response, anyone else have anything to add?
 

Chinewalker

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Re: '68 Mercury 110 9.8hp

Have you actually checked to see if it is running on both cylinders? Alternately pull one of the plug wires when the motor is running - use a rubber glove or insulated pliers. If the motor keeps running with no change, then you know that's the cylinder it's running on. If it dies completely, then you know it was running on the one you pulled off...
 

XTRME 94

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Re: '68 Mercury 110 9.8hp

Have you actually checked to see if it is running on both cylinders? Alternately pull one of the plug wires when the motor is running - use a rubber glove or insulated pliers. If the motor keeps running with no change, then you know that's the cylinder it's running on. If it dies completely, then you know it was running on the one you pulled off...

Haven't tried doing it that way, but I have checked the plugs and they appear they are both firing the same, and have a normal amount of carbon on them. Nothing out of the ordinary.
 

Faztbullet

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Re: '68 Mercury 110 9.8hp

The replacement coil if it is black or blue in color it will not work on that engine...
 

XTRME 94

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Re: '68 Mercury 110 9.8hp

The replacement coil if it is black or blue in color it will not work on that engine...

???? Confused ???? The original coils were black, and both the replacements are black. Can you please explain?
 

Faztbullet

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Re: '68 Mercury 110 9.8hp

The the blue/black coils use a common ground internally on the primary & secondary side of the coil. This motor requires the ground of the primary and secondary of the coil to be separate as as the points drive the negative side of coil to ground causing the coil to generate spark on the secondary side..This motor needs the orange,red or chartreuse green.Here are pic's of my 9.8...


boat 006.jpgboat 007.jpg
 

XTRME 94

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Re: '68 Mercury 110 9.8hp

The the blue/black coils use a common ground internally on the primary & secondary side of the coil. This motor requires the ground of the primary and secondary of the coil to be separate as as the points drive the negative side of coil to ground causing the coil to generate spark on the secondary side..This motor needs the orange,red or chartreuse green.Here are pic's of my 9.8...


View attachment 119787View attachment 119788

Okay. Your motor is different from ours as our coils are under the flywheel (red top).

boat motor.JPG
 

Faztbullet

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Re: '68 Mercury 110 9.8hp

Thats a 1966 or earlier. From what you posted its: (A) carb is running out fuel due to air leak or weak fuel pump diaphragm or (B) clogged inlet filter on carb (C) restricted high speed jet in carb.
 

Chinewalker

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Re: '68 Mercury 110 9.8hp

FB - '68 still had a standard points/coils/condensers ignition with the coils under the flywheel. It did not have the Lightning Energizer low-tension magneto with the external coils.
 

XTRME 94

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Re: '68 Mercury 110 9.8hp

FB - '68 still had a standard points/coils/condensers ignition with the coils under the flywheel. It did not have the Lightning Energizer low-tension magneto with the external coils.

Thanks! As we were going off the serial #. Guess it's time to try and rebuild the carb.
 
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