Mercury 2+2 - How does it work?

[convergent]

I have a '93 Mercury 115HP and my understanding is it is a 2+2... sometimes runs on 2 cylinders and other times on 4. First question is if my motor is a 2+2 or not? If it is, can someone give me an overview of how it works in concept, and then what I would experience in day to day use?

 

[Faztbullet]

Re: Mercury 2+2 - How does it work?

If its a 4 cylinder engine it is a 2+2 style. To keep it simple the lower to carbs do not have adjustments and passageways like the top so below 1800 rpm they supply just enough fuel to keep pistons from siezing. There is a accelerator pump on linkage to help to overcome this at throttle up (1500-1800rpm) and bottom carbs start to work.

 

[Dave1027]

Re: Mercury 2+2 - How does it work?

There is no idle circuit on the lower two carbs. That means no gas to them at idle so they don't fire. As you open the throttles, the main circuit engages and begins allowing gas to those bottom two cylinders and they fire. The accelerator pump is to assist in getting those bottom two going. I heard Merc made it this way because there was no other way to make a two stroke inline 4 idle smooth.