1987 Mercruiser 140 timing issue?

[1987sylvanoffshore]

Motor serial # B403505 from what I can read.
I can't seem to get the RPM's down low enough (650-700) to time my motor properly at 6 BTDC, it runs too rough. When I timed it(1000 RPM's in gear tied to my dock)it was 4 BTDC. Should I try to adjust the secondary idle screw on the carb? The motor runs absolutely fine except for low idle 650-700, at 1000 RPM's in gear it runs fine. What should my next step be?

 

[Bt Doctur]

idle speed should be 800 ish ,in gear, in the water. you have 2 screws a idle mixture and a idle speed.adjust the mix so that it runs the best, then adjust the idle speed, then set the timing.readjust idle speed if necessary

 

[1987sylvanoffshore]

Ok that makes sense, I did everything in the opposite order.

 

[1987sylvanoffshore]

One more question that I forgot to ask,
Should I do the carb adjustment in gear or in neutral?

 

[achris]

Idle speed and mixtures (if you have 2 screws for mixtures in the carb base they must be adjusted at the same time, and evenly. You can not have one at say, 2 turns out and the other at 4. Both screws are primary mixture screws, one for each barrel) and MUST be adjusted with the engine in forward gear and unhindered. That is, it can't be tied to a jetty. For this you need 2 people....

Chris....

 

[1987sylvanoffshore]

Why can't you be tied to a dock in forward gear for these adjustments?

 

[achris]

Because that adds load to the engine. And that's what Merc say on the manual.