timing question

[patchesII]

if my timing has a 6* spread through the cylinders are the switchboxes the normal culprit. just went out and timed my cylinders and got this. thanks in advance, erik
if my brain is not fried today i come up with every .006" of piston travel is equal to 1*

#2----20* #1----17*
#4----20* #3----19*
#6----21* #5----23*

[Jay Smith]

Eric,

Are those numbers at total timing? Why is #1 set at 17* when that should be the one that you set at 25* mechanically with the timing screw

Just curious,
Jay

[patchesII]

yeah jay that is total timing. i haven't adjusted the timing since putting the powerhead together. if i'm correct in my timing if i set #1 at 25 that would put #5 at 30-31. my flywheel is indexed at 0 and 25. i'm using one of your dial indicators to index the spot the timing light is flashing on and using .006" per degree these are the numbers i come up with. the starboard side is kinda all over the place.

[Jay Smith]

Call me Erik...........1 281 576 5088

Jay

[Scott in MN]

I have the same problem, swapped everything from another motor except coils and problem still exists...smoked #5 last time out so I get to start over with a fresh motor next spring and am going to start buying new electrics starting with coils until problem goes away....gets very frustrating...

[patchesII]

i just got this motor back together after smoking #5 back in june. i take full responsibility for that mishap. i tried to run 205 lbs of compression with aces, and to add fuel to the fire i leaned the box down way too much. totally stupid moves. now i'm wondering if this screwy timing wasn't the final straw.

[patchesII]

just back in from the garage where i re-indexed the flywheel and set the timing on #1 to 25* to see if it would bring the numbers in line. heres the new numbers. i double and triple checked these. thanks to jay for taking the time to help. what do ya'll think. there is now only a 4* spread. i could put #6 at 26 and that would put the lower cylinders at 22* but i hate it not being right. guess its time to start swapping parts. wanna place any bets on what it is

#2----27* #1----25*
#4----25* #3----28*
#6----29* #5----27*

[Jay Smith]

Erik, the high timing values on #6 and #5 still concerns me, I'd maybe change the trigger and repeat the test. But the move we talked about brought things closer but still no cigar.... Please post back after the trigger change and new round of tests are performed..

Peace,
Jay

[marshan162]

Do you have both bias terminals on switch boxes linked together?

[sschefer]

I saw this once with a mixed set of pistons in a Rat Motor. Haven't seen it on a outboard yet. Give me a few more years and I'll probably make it happen. On that one the piston height would have been correct if the wrist pins were at the same height. We were young and just wanted to make it run for Friday night cruise.

[mrcrsr]

last engine i had here that did that turned out to be the switchboxes

[ChrisCarsonMarine]

In 1976 I was in the mercury factory certified class.We [the class and instructors]were learning the "new" ignition system used on the 175.We ran tests on cranking and running voltages on various components,as well as olms readings on coils,trigger,stator,etc...actually helped compile information to use as a troubleshooting guide for a motom basicly no one knew anything about.As any merc oldtimer,like me,knows these motors burned #5 if you looked at them hard,then #2.We were told in school this was due to the fact the crank was not ground at 60 degree interval spacing on the journals,and #2 and #5 had the most timing because those journals were advanced more than the rest.Those cllinders always got bigger main jets to cool off those cylinders,and if you look in your pile of heads and blocks,you'll confirm probably 80% of melted pistons are #2.Am i the last one alive that remembers this,I don't believe I made it up?Johnson,Ramsey,you still out there?

[patchesII]

if i can just get it down to a couple degrees difference i would be happy. then i could set the high side at 26 and have the lows at 24. i have an old set of switchboxes that i can put on. i'll have to find a trigger. i'll update the post with what i find.

[RLP]

trigger
also cant hurt to look at the trigger magnet on flywheel base.

[Jeff_G]

After indexing your flywheel properly and doing a timing check on each cylinder, time the engine to the highest reading cylinder. Then re-check timing at wot.
When indexing your flywheel, do as Lightnbug said. Forget piston travel.