Timing on 81 40 hp 2cycle Mercury Outboard

"Hello All,

I am trying to

"Hello All,

I am trying to time my engine (1981 Mercury 40HP, serial #5897367, Model# 1402R) but can't seem to figure out which dots on the flywheel to use. My repair manuals (I have both Seloc and Clymer manuals) makes reference to "2 dots" and a "straight line" on the flywheel, but I have multiple dots on my flywheel, and multiple degree timing line marks? I have attached some pictures which show the dots and markings on my particular flywheel. Both of my manuals describe lining up these "2 dots" (for pickup timing) and the "straight timing line" (for max. advance timing) with the timing pointer. Since my flywheel doesn't appear to have these "2 timing dots" or "straight line", I'm at a loss? Both my manuals refer only to the dots and straight line for the ATDC and BTDC settings, no degree numbers are specified in either of my manuals, just these darn dots/marks. I bought the engine a few years back, so i am not sure about the history of this flywheel. It may not have been made for this particular motor but it does work, it's just missing the "2 timing dots" and the "straight timing line" my manuals make reference to. Since I do have degree marks stamped on my flywheel I figure if I can determine what degrees correspond to the "2 timing dots" and to the "straight timing line mark", I'd be good to go. Does anyone know what degrees correspond to these timing marks on the flywheel? Or the ATDC/BTDC specifications for this engine?

Thank you for the help, it is appreciated.

Flywheel Pic1"">

Flywheel Pic2"">

Flywheel Pic3

"Max timing is 27, base timing

"Max timing is 27, base timing is 2-5 btc. The max timing shouldn't have changed unless someone messed with it. It's better to run at 25 then at 29. It can only be checked accuratly at max rpm
There is a section in the merc manual for link and sync, its really the only manual to use."

"Thank you for the help JB. I

"Thank you for the help JB. I agree, I need to get me a merc manual. The Seloc and Clymer do OK for some stuff, but they both missed the boat (no pun intended) with the timing procedure. For the base timing, is that done is forward gear at any particular RPM or is this done at idle/neutral with no load? Right now at idle/neutral/closed carb she is sitting at 2 degrees ATDC and turning up around 1000 RPM. Does this sound right to you? This is the first time I have ever timed her (or any OB engine for that matter), and you are right, someone I took it to to work on her messed with the timing and messed with her good..!!! Any recommendations on where I can order me a Merc manual? Thank you again for the help..."

"I have a 83 40hp merc. Mine r

"I have a 83 40hp merc. Mine runs like a top, when i checked the timing on mine she was sitting at 3 degrees. cant check max timing since i dont have a test tank, and dont want to hang on the back of the boat while its running WOT. Hope i helped."

"The max timing won't chan

"The max timing won't change on these models unless messed with. I too have an 83 40hp, nice running engine. Keep an eye on the starter bolts, when they get loose it will crack the front case. Also keep the splines on the crankshaft slightly lubed to prevent it from welding itself togeather."