little more explanation on sync timing

ReeseK

Seaman
Joined
Aug 3, 2003
Messages
52
I could use a little more description if possible to the sync explanation in the next paragraphs I have all the test equipment required except the tool to test tdc.<br /><br /><br />Timing Event One - throttle pickup.<br />As the throttle is advanced, the spark timing advances toward TDC and then to before TDC. As the timing is just passing TDC the """"1st(minor)throttle pickup should hit"""" and start to open the carbs. Use the timing light. Adjust the tang or trigger screw to make this a reality. All of them are speced different, but if the 1st pickup hits at """""3-4 degrees BTDC advance"""" - you win. Use the timing light with a friend cranking it to complete this setting.<br /><br />the way I read this is with someone turning the engine over with the throttle fully closed my timing light should be flashing on 3-4 degrees on the flywheel. on a 115 1976 6 cyl do I adjust the left or right screw that turns the distributor cap? left being closest to the carbs.<br /><br />Timing Event Two - max advance.<br />As you continue to advance the throttle the timing will advance while the carbs slowly open a bit more. The next adjustment is max advance, this is the point where the distibutor (or trigger) can advance no more. Set the max-advance stop to 21 degrees for "direct charge" inlines and 34 degrees for the older crossflows. Use the light, - err to the side of caution.<br /><br />I read this as I open the throttle the timing will advance to 21 or 34 (I don't know which.) when I open the carbs to all the way.<br /><br />also is it normal for a small amount of gas to get in the catch tray at the bottom in front of the carbs when starting?<br /><br />I have a book but it is a little more greek to me at this time.<br /><br />pictures would be great but an explanation of what I am adjusting or rather which screw I am adjusting would be great.<br /><br />thanks a million to those who read this through and say "wow doesn't he understand anything what an idiot". then still help me.
 

Clams Canino

Commander
Joined
Jan 10, 2004
Messages
2,179
Re: little more explanation on sync timing

Originally posted by ReeseK:<br /> I could use a little more description if possible to the sync explanation in the next paragraphs I have all the test equipment required except the tool to test tdc.<br /><br /><br />Timing Event One - throttle pickup.<br />As the throttle is advanced, the spark timing advances toward TDC and then to before TDC. As the timing is just passing TDC the """"1st(minor)throttle pickup should hit"""" and start to open the carbs. Use the timing light. Adjust the tang or trigger screw to make this a reality. All of them are speced different, but if the 1st pickup hits at """""3-4 degrees BTDC advance"""" - you win. Use the timing light with a friend cranking it to complete this setting.<br /><br />the way I read this is with someone turning the engine over with the throttle fully closed my timing light should be flashing on 3-4 degrees on the flywheel. on a 115 1976 6 cyl do I adjust the left or right screw that turns the distributor cap? left being closest to the carbs.<br /><br />NO, ADVANCE AT FULLY CLOSED WILL BE RETARDED, YOU ARE READING EVENT 1 - AS YOU OPEN THE THROTTLE OFF IDLE. YOU WOULD ADJUST THE PICKUP ON THE TOP CARB FOR THIS PART, NOT THE DIST<br /><br />Timing Event Two - max advance.<br />As you continue to advance the throttle the timing will advance while the carbs slowly open a bit more. The next adjustment is max advance, this is the point where the distibutor (or trigger) can advance no more. Set the max-advance stop to 21 degrees for "direct charge" inlines and 34 degrees for the older crossflows. Use the light, - err to the side of caution.<br /><br />I read this as I open the throttle the timing will advance to 21 or 34 (I don't know which.) when I open the carbs to all the way.<br /><br />IT'LL HAPPEN BEFORE YOU OPEN THE CARBS ALL THE WAY, AND FOR YOURS IT'S 21 AND NO MORE. 20 SINCE YOUR TDC IS SUSPECT.<br /><br />also is it normal for a small amount of gas to get in the catch tray at the bottom in front of the carbs when starting?<br /><br />YES<br /><br />I have a book but it is a little more greek to me at this time.<br /><br />pictures would be great but an explanation of what I am adjusting or rather which screw I am adjusting would be great.<br /><br />thanks a million to those who read this through and say "wow doesn't he understand anything what an idiot". then still help me.
See my all caps reply in post. That said... I do feel you outta take it to shop for llink and synch, with the manual AND my post to work with - this might not be a job for you. Sorry dood.<br /><br />-W
 

swdockter

Cadet
Joined
Mar 14, 2005
Messages
12
Re: little more explanation on sync timing

ReeseK, <br /><br />You really need to get a Merc factory manual and study the pictures/steps before you start playing with the timing. Go to ebay and get one. I got my 86 manual for about $20. That was cheap, they're like collector items these days. :rolleyes:
 

ReeseK

Seaman
Joined
Aug 3, 2003
Messages
52
Re: little more explanation on sync timing

I have a seloc manual but it described the process a little differently with not many pictures I was going from one area of the book to the other to locate pictures that had descriptions with them and just for my year of boat. I have some experience with a Johnson 35hp I definetly would never be afraid of rebuilding a lower unit. they are all basicly the same. but I went from 1 carb and easy timing adjustment to 3 carbs and a new set of terms for the same parts. I can figure almost anything out if given time. mostly out of necessaty (lack of money for a repair shop). I never start anything until I am for sure I understand it fully and I am sure I can do it or that I can at least not mess it up worse. I just wanted a more detailed description. understanding the timing advance or retard is basicly low speed idle, this alone helped make a heck of alot of understanding come into play.
 
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