Why is the '72 650 primary pickup 0-2 degrees and all others are 3-5 degrees?

[franklenz]

Why is the primary pickup setting on the mercury 650 1972 different than all of the other years? The reason I ask, is because my carbs are off of a '74. After setting the link and sync to near perfect with the primary pickup at 0-2, my idle timing turns out to be around 5 degrees btdc, and my idle lever causes the carbs secondary pickup to engage. I figure that if I start with the pickup at 3-5, my idle lever won't cause the carbs to hit their secondary pickup, and I would start off at a good timing with little adjustment needed on the idle stop screw.

Thoughts?

 

[Chris1956]

There are different idle pickup timing specs for distributor ignition and ADI ignition. Which do you have? At first glance, it sounds like you are doing something wrong in your link and synch.

I do not understand what you mean by idle timing. You set the idle pickup timing, set the max timing, and then adjust the idle to 800RPM or so. Not sure what "idle timing" is, as you reference it.

 

[franklenz]

After I got the idle between 800-1000 out of gear, and 500-600 in gear, with the throttle pickup set at 0-2 degrees btdc. Out of curiouosity, I went back to see where the timing landed at. It was hitting at 5 badc. That's because I had to tighten the idle adjustment screw to set the Roma to the right point. Adjusting the idle stop screw turns the rotor and makes fine timing adjustments when setting the idle.

I just went back to see where the timing ended up at....which was about 5-5.5 btdc.

The distributor, and the carbs are frankensteined off of other motors and unknown years. I was wondering if I should just start the whole link and sync with the primary pick up at 3-5 btdc - swing that's where it ended up anyways, and this should stop the secondary pickup from hitting so soon.

It runs great, http://youtu.be/byc3MmCgnP4 , but was curious as to why the pickup point changed - I might need to be at 3-5 instead on the manuals 0-2 due to the different year parts.

Thanks for the help! Please let me know what you think.

 

[franklenz]

Roma = rpms. Autocorrect. Also btdc for the other misspell. Sorry.

 

[franklenz]

Ha! I just read my post again...tons of typos. I'm at a fishing hole right now and am trying to type on my phone...

 

[franklenz]

I just did a quick link and sync in a barrel and started at 3-5 degrees btdc. It was a lot easier to keep it running and idling 900, 550 in gear. Much easier. Also, the secondary throttle pickup does not engage so much when using the idle lever in the controls. Much better.

 

[Chris1956]

A lot of those distributor CDI ignition units call for idle pickup timing of 4-6* BTDC, and max spark advance of 21* BTDC. Of course, I have only worked on motors with the proper ign and fuel systems.....

 

[franklenz]

They are definitely the right carbs and switch box, distributor, etc. the 1973-76 call for the same part number on those too. Which makes me wonder why the timing is different for the 1972 - I figured it should be the same as the other years. There has to be something that makes it different - even if there just might be a manual change that I'm not privy to.

 

[franklenz]

I will video the whole link and sync process and put it up on YouTube for review. Maybe I am doing something wrong and am just so stubborn that I can see the obvious. Give me a couple of days.

 

[Chris1956]

Are you loosening the two 5/16" bolts on the brass distributor collar? That allows you to adjust the idle pickup timing directly, by altering when the "fingers" open the carbs. That adjustment is not obvious.

 

[franklenz]

You might be talking about an earlier model.

 

[franklenz]

I will do the video this week. There isn't a good video on link and sync for the 72-76 mercury 650's. It should be used a lot, and alleviate a lot of questions in the forum.

I did spend today (all day) on the boat. I did come to the conclusion that one or both of my floats are set too high - I believe it's the top one. When I idle for a while, the motor floods a little - then, it bogs a little on the hole shot. I will eventually run it at wot for a while, then go back to idle in gear. That's when it purs perfect. Give it a minute for the bowls to fill up, then it will rumble at idle. I think it's the top float, cause I can see an excessive amount of fuel smacking the shutter - only after it idle in gear for a minute and the bowl is full. Or, maybe something came loose when I was putting them back together after the rebuild. I will check it before I video the link and sync.

 

[Chris1956]

A '73 IL4 distributor definitely has that brass collar adjustment for idle timing pickup. I have not looked at a '72 IL3 motor, but it is logical to think they share distributors, excepts dist. caps.

 

[franklenz]

Can you post a pick. I can't find what your talking about.

 

[franklenz]

No Title

If you're talking about the ring that goes around the distributor and hold the cap in place, no..I did not loosen or adjust this. You cannot turn just the distributor cap like on a car distributor because the is a triangular cutout in the cap that allows room for the trigger wiring bracket. This is an intentional design that prevents just the cap from turning. If you attemp to turn the cap, you will snap off this wiring bracket and end up having to drop $400 on a new distributor. I made this mistake about 6 years ago on my first 1974 650. I found a pic of it.

 

[franklenz]

No Title

This is what I'm looking at.....(this is not my picture though, and I did not write those labels in red). I've been using the idle stop screw at the bottom right to adjust my idle speed - this picture labeled the trigger tang screw to adjust his idle speed. Should I be doing that instead? Then set my max timing when It idles in gear good? Everything else I've read says no.

 

[Chris1956]

OK, that throttle and distributor linkage is a lot different than a '73 IL4 motor. The very bottom right screw looks to be the idle stop screw. The throttle cable must be adjusted to push the throttle to that screw setting. There needs to be some way to alter the position of the distributor without changing the position of the carb throttle plates, but I do not know what it is.

Since I am unsure, and Hurricane Sandy took my service manual for that motor, I need to keep quiet. You might be able to find a Mercury on-line manual for free. Try the boatinfo.no website

 

[franklenz]

Thanks. I have a Clymer and it blows...like a hurricane!