Spark advance 1977 Ford Marine 175 hp 302 Engine

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RogerBoat

Seaman Apprentice
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Mar 5, 2011
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37
I am proud to say I completely replaced all the ignition parts, set timing to 10 Degrees per Seloc manual and boat is running better than ever.

I am not so proud to find out I didn't know there is a difference between "initial timing" and "total advance timing"and that total advance is the more important setting to get right. 2 hours on internet did me no good. So I am looking to you expert folks to set me straight.

I am using Seloc Manual. It says "Timing marks Degree" should be 10 Degrees (BTDC) which I presume for idle RPM.

Then it has an abbreviation "MFD." which states .25-.28. What is that....is that what "total advance timing" should be? If so, what engine rpm should this take place? I presume this is degrees BTDC and takes place before 3000 rpm , at least that is the rpm I usually cruse at.

As usual, I am wrapped up in fine details and probably want to hear that setting the engine at idle (600 rpm) is enough and forget all the rest. What do you think?
 
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RogerBoat

Seaman Apprentice
Joined
Mar 5, 2011
Messages
37
Well!!! Thanks Supreme Mariner Alldoge,

I realized how dumb my question about MFD was as soon as I released the message...didn't visually take note that the values were fractions. To my credit, I only saw 25-28 which happens to be the values on the seloc graph for rpm's above 3500.

I wish I had understood what MFD meant when I was struggling with finding the right condenser. Would have saved me a lot of time.

But now about your chart....

It says, "add value to basic Timing setting for total advance." If I understand your information correctly: I should set at idle, to 10- 13 degrees (Before Top Dead Center) then take the value for 4000 RPM (about 24 degrees) add them together for a range of 34 - 37 degrees? Then take the RPM up to 4000 and expect to read a range of 34 - 37 on the flywheel?

Sorry I am having a hard time understanding this...Seloc manual agrees with 10 degrees at idle but the graph only suggests I should read 27 Degrees at 4000 RPM.

Appreciate if you can set me straight about this.
 
alldodge

alldodge

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Staff member
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Mar 8, 2009
Messages
42,610
No
Timing is set at 10 BTDC and the distributor will provide additional advance between 10 to 13 degrees.
Total advance = 20 to 23 degrees
The 3 degree difference is based on the spring tension on the flyweights inside the distributor
 
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RogerBoat

Seaman Apprentice
Joined
Mar 5, 2011
Messages
37
Gotch ya....Thanks...Total Advance 20 - 23 Degrees. I probably knew all this 25 - 30 years ago when mechanically tuning engines was a must...Now at age 76, I have forgotten. It may be time to sell this 43 year old boat before I have to fix something else. But the problem is....there aren't many parts left that are more than 4 years old and I can't find another boat I like better.
 
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