1972 mercury 800 timing ??/

My Motor seems to run pretty good but I am a little concerned with the timing,I have read the link and synch procedure and have read the manual several times and still not sure. Number 1 the only thing on my flywheel as far as markings are 3 dots and if I am doing this right, I used a dial indicator to find TDC on Nr.1 piston, the 3 dots line up with the arrow on the distributor gear thats good everything in a straight line. Now on my Motor I dont have a Timing pointer,although on the top of my engine cowl is a timing gauge,so I thought I would just put a mark on the flywheel that matched the TDC marking on the cowl when the Nr.1 piston is @ TDC. According to the link and synch as I advance my throttle the timing advances as well. The throttle pickup should start to open the carbs around 3 to 4 degree's BTC well in my case this doesnt happen.Mine seems to be Idleing at 3 to 4 degrees BTC and start to open carbs at 8 to 9 degrees BTC. So when I set max advance to 23 degrres BTC I dont think thats correct. Any input on what I am doing wrong?? Thanks Guy's

Re: 1972 mercury 800 timing ??/

There is supposed to be a decal on the flywheel that shows the timing. The timing pointer is the mark on the cowl support.

It sounds like your idle pickup is misadjusted. The carbs should start to open at 3-4* BTDC. Do you know how to adjust the brass collar on the distributor, to open the carbs at the correct moment? There are two 5/16" stainless bolts on the underside of the brass collar. These are loosened and the brass collar moved to contact the carbs, when the timing reaches 3-4*BTDC.

Max timing needs to be 21* BTDC. Set it with the max spark advance screw above the distributor. use the idle stop set screw to set minimum RPM, usually about 900RPM.

Re: 1972 mercury 800 timing ??/

Okay didnt know what those 2 screws were for and on top of that they were loose. I unfortunatly dont have any marking on the flywheel except the 3 dots. I found TDC and made a mark on the flywheel. Now is max advance 21* TDC set just before the secondary throttle pickup opens or did I misunderstand and that it should be @ complete WOT. As for your question on how to adjust the brass collar so the carbs start to open @ 3-4* BTDC I would crank the motor and with the help of my max advance screw and the timing light find 3-4* BTDC so I can keep the distributor in that position and then adjust according my guess. Thanks for the response.

Re: 1972 mercury 800 timing ??/

My timing decal that shows TDC all the way up to 50* BTDC is on the upper cowl support no marking on the flywheel.

Re: 1972 mercury 800 timing ??/

How do you know what the timing is if you have no decal?

The max spark advance set screw is supposed to limit spark advance to 21*BTDC. I do not think decals are available.

Perhaps with careful measurement of the flywheel's circumference, you can figure out where 4* and 6* BTDC and 21* BTDC are located and mark them. Those are all you need.

The plastic finger on the distributor should just touch the carb throttle yoke when timing is 4-6* BTDC. The max timing set screw should stop the distributor rotation at 21* BTDC. The economizer collar will allow the carbs to open all the way, after the distributor has reached max advance.

I recommend a merc service manual.

Re: 1972 mercury 800 timing ??/

I added a Pic so you can see what I am asking about I maybe way out in left field somewhere on this one. In my manual it shows different setups for my Model but unfortune has it that mine has little info.Mine doesnt have a pointer on the engine and no decal on the flywheel. I have 3 dots in a row on the flywheel for lineing up distributor shaft, arrow on the distributor gear,3 dots and the center of the crankshaft.In my pic the marking to the right are the 3 dots all lined up at TDC.To the left that marking lines up with TDC with the cowl timing decal.In my mind I should be able to go on to link and sync process???? Does this shoe fit???:redface:

Re: 1972 mercury 800 timing ??/

Ok, You have the timing marks on the cowling support. You need to make sure the 3 dots are TDC, they are for timing the distributor, but may ne be exactly TDC.

Since you have a dial indicator, you can zero it at TDC. Now back off the flywheel a bit, and then rotate it in the direction of motor running, until it just touches the dial indicator. This should be TDC. Mark it on the flywheel with a thin white line.

Now you can follow the link and sync procedure I outlined.

Re: 1972 mercury 800 timing ??/

Thank You very much,that was the answer I was looking for.Thank you,Thank You!!

Re: 1972 mercury 800 timing ??/

oopps