What should my max spark advance be?

[hoosiercaver1]

I am trying to do the link and sync on my 1970 merc 1150 and I've read the article on here about how to do, but I've got a couple of questions. In the thread on how to sync it says the max advance should be 21 deg for direct charge, but there is a sticker on the front cowling that says 27 deg for the timing. What should I set it at? Also the article says to remove all plugs but the #1, if I do this do the others need to be grounded to the block as I am setting the timing? Why do u need to remove them? I don't want to screw up my switch box or coil by not doin something right. Any help would be great. Thanks

 

[dlplost]

Re: What should my max spark advance be?

Timing..Allways use the sticker number if there is one.

Plugs??--I don't know that one..

 

[redjmp]

Re: What should my max spark advance be?

Timing..Allways use the sticker number if there is one.

Plugs??--I don't know that one..

Not on an older motor that was made when the fuel was better.
Modern fuel is not as good so to prevent detonation use 21*...

 

[jimmbo]

Re: What should my max spark advance be?

I do recall some service bulletins about the octane levels and overall quality of the liquid provided by the oil companies and how it affects the timing on older engines. One bulietin said 23 degrees max, later revied to 21 degrees, and somehow I recall 18 degrees being mentioned.

 

[hoosiercaver1]

Re: What should my max spark advance be?

Ok in glad I asked. I'll go with 21 deg and see how it does. Any suggestions on what to do with the other plugs while setting the timing . Will it hurt to just crank it like normal with all the plus in and wires connected and not choke it, cause it will never start cold if I don't choke it.

 

[oldman570]

Re: What should my max spark advance be?

All the plugs will need to be out, except #1, and grounded inorder to spin the motor over faster to set the WOT timming. With the plugs in the motor will not spin fast enought to get a close setting of the timming. Also have muffs on the motor with water running as there is a good chance you could ruin the impeller. Always check the WOT timming on the water, with the help of a friend, as it still could need a change. Grounding the plugs will make sure the electrical system will not be hurt. Be sure that the fuel is disconected and no fumes are near.
Oldman570

 

[hoosiercaver1]

Re: What should my max spark advance be?

When u say to check it on the water with a friend, is that under load, or just on the trailer?

 

[oldman570]

Re: What should my max spark advance be?

The final check should be done under a load in a test tank or on the water. Testing it on a trailor will creat more load than what the motor will be under when actualy running on the water as the RPM's will be lower. Be sure all tools are tied off to the boat. Not realy a safe way to do checks, but only way it can be done if no access to a test tank. You can set timming on the trailor or adjust it alittle at idle then check it with a light at WOT with a friend till you get it set to manufactures speck or alittle less. Test tanks and test prop wheels are alot safer and more persice settings can be done. I would set it on the trailor and see what it is when on the water,
and go from there , if your not satisifed with the settings.
Oldman570

 

[Moody Blue]

Re: What should my max spark advance be?

Timing..Allways use the sticker number if there is one.

Not in this case. As mentioned those sticker numbers were based on the fuel quality available 40 years ago. Go with the 21* for safe operation of your motor. This is a generally accepted number.

The reason for grounding the pulled plugs is to prevent undo strain on the ignition components. The ignition system will always attempt to generate a spark to ground regardless of how big of a "gap" there is. The bigger the gap the higher the voltage and hence more energy is dissipated with a larger gap. It is also possible that the high voltage could "jump" to ground elsewhere if unable to bridge the gap at the plugs, and this could damage some components.

 

[Jumbo3905]

Re: What should my max spark advance be?

Would these timing numbers of 21* apply to a 1987 60 hp as well or is there a more suitable WOT timing number for them?

 

[oldman570]

Re: What should my max spark advance be?

The specs on a 1987 60 Merc call for 23 but I would go with 21 for the WOT timming and see how the motor preforms. I belive it is better to play safe rather than take a chance of ruining a motor. Watching the p;ugs will tell what that motor is realy doing and the timming can be advanced if one wants to do so latter.
JMO
Oldman570