Help needed on timing a mercury 1985 75hp

[ss von scalliwag]

Hi to all,

I have just completed a rebuild on a mercury 1985 75hp 4cyl. due to the crankseals failling.....
My question to anyone who is familiar with the ignition system on these engines and also the 80hp built a few years before my one.
I am trying to set up the primary pick up ignition timing and I just can't seem to get it right.
I have read the excellent thread by clams canino on this forum about lync and sync but it doesn't seem to apply to this particular engine. The manual specs are completely different as to what is suggested by clams.
What I would like to know is what should the advance/retard be set on at idle when CRANKING the engine on the starter motor. (manual= 5-8 ATDC and clams's post = 3-4 BTDC)
I am really confused as to what it should be set at Any help on this would be extremly helpful as I have invested a lot of time and effort getting it this close to running again but seem to have fallen flat on my face at the last hurdle!
Seriously any suggestions would be really appreciated

 

[verado7]

Re: Help needed on timing a mercury 1985 75hp

your motor requires the use of a dial indicator to first set up tdc to the pointer -

first get a dial indicator atthe tool store -

remove all spark plugs and put the dial indicator in the #1 spark plug hole -turn t5he flywheel until the piston is at tdc - dial indicator will go up then gow down -you want to get it to the highest reading before dropping - then set the dial to zero

turn the flywheel counterclockwise until you see 0.464 then keep going another 1/4 turn - now come back clockwise until the indicator shows 0.464 again check that the timing pointer is now alighned with the tdc mark on the flywheel - if not loosen the nut and adjust the pointer . now you can go about setting up the primary pickup as per manual

there is no primary pick up timing number for your motor it merely involves a throttle pick up adjustment - and max timing is 23 btdc.

get a "seloc" brand manual and read pages 6-25 and 6-26

 

[ss von scalliwag]

Re: Help needed on timing a mercury 1985 75hp

Verado,

Thanks for the reply. I have setup the timing pointer SPOT ON. I have the seloc manual you have refered to but however they do not specify how to set up the primary pick up synchronizing, they just mention it briefly and don't list the specifications.
Trust me it has one, what I would like to find out is what should it be set at whilst the engine is being cranked at by the starter motor, not whilst the engine is running.
Some one out there must have had this problem before, as the clymer manual states it at 5-8* ATDC while engine is running at idle (550-650 rpm) in forward gear.
This is my problem, I cannot get the engine close enough to idle to follow this procedure.
Any other suggestions out there
Many thanks in advance.

 

[verado7]

Re: Help needed on timing a mercury 1985 75hp

if you can't get it to idle down then you have other issues - possibly a weak trigger . you need to fix that problem first - sorry i checked my manual again and could not find any primary adv. numbers for your motor - just a refrence to adjusting the pick up on the pages i mentioned - there are specs for other 75 hp motors but not yours in my seloc manual and i cant see why my manual would be different than yours . i would follow those directions on the pages and set the wot timing - if your still having timing issues - again -you could have weak trigger . you list 2 different manuals - a clymer and a seloc - i'd go with the seloc manual -

 

[ss von scalliwag]

Re: Help needed on timing a mercury 1985 75hp

Verado thanks again for the reply but we seem to be going round in circles here.
I will just reliterate for others here on the forum that do actualy have experience with these particular engines, my outboard engine DOES have a primary pick up ajustment dispite the fact that the seloc manual does not list specifications. The clymer manual does however have the specifications but the setup procedure involves getting the motor in forward gear and letting it run at idle. It does not list what it should be set when the engine is being turned over by the starter motor.
The max advance is already set at the recomended spec. The stator and trigger etc have been checked and are fine. The reason why I cannot get it to idle is simply becasuse the low speed timing is out of whack and needs seting up again.
My question is what is the primary pick up timing set at on this outboard engine at cranking speed.
Some one must have the answer or at least be able to give me a seting that should get it close enough to be able to fine tune.
Many thanks in advance

 

[ss von scalliwag]

Re: Help needed on timing a mercury 1985 75hp

Right, just an update. I got it pretty close. She's running at 800 rpm atm in neutral, but the timing is set at 5* ATDC at the point when the throttle pick up cam just contacts the carb cluster pin.

Is this about right ?! because its running fairly smooth, but I just want to make sure that the timing is perfect before I make any final adjustments with the carb idle screws. (roughly 1.5 turns out atm)

Any thoughts would be great.

Cheers.

 

[verado7]

Re: Help needed on timing a mercury 1985 75hp

thats sound right - just make sure you set it with the engine in forward - and the pickup cam should just touch the carb cluster . that sets your primary pickup time and synch .