Conflicting timing specs

[Dave1027]

I have a '88 100 hp 4 cylinder 2+2 Merc that has two different max timing specs listed. My Merc manual has it as 27 degrees BTDC @cranking speed on one page and then 25 degrees on another. Both pages say the timing is retarded to 23 degrees BTDC @ 5000 rpm. I would think that the 27 degrees is a typo but there is a sticker on the front of the carb cover that says 27.

So which is correct?

 

[Faztbullet]

Re: Conflicting timing specs

Maximum Timing @ 3000 RPM.....23
B.T.D.C.
(@ Cranking Speed).....25
B.T.D.C.)
Idle Timing 2
- 4
B.T.D.C.

 

[Dave1027]

Re: Conflicting timing specs

Thanks for that confirmation.

Do you have any idea why the factory sticker on the front of the motor says 27? Could it be because '88 was a first year for this design?

 

[Faztbullet]

Re: Conflicting timing specs

Likely but fuels and engine design has changed since 1993, the pre-93 engines are 105 CID and the 94-up are 115 CID

 

[verado7]

Re: Conflicting timing specs

the 27 deg. is for timing in a test tank

you set it timing 2 deg. less when using the cranking speed method as a safe measure to not exceed 27deg. at 3000 rpm

the idle timing 2-4 deg - is adjusted by a screw on the linkage that rotates the trigger ( under the flywheel ) - it is for starting /idling and just in gear .