[BJM]

My 92 115 Mariner runs on 2 cylinders below 2000 RPM. The top 2 kick in only above 2000 RPM. How is this accomplished? Can it be bypassed?My other question is this, if the carbs are halting fuel delivery to those cylinders, how are they lubricated while not firing?

[Kenny Bush]

The control module kills the spark to those cylinders. Fuel and oil are still going through.

[MurdockJr]

BJM the bottom two carbs have no idle circuit. Bottom two carbs kick in at about 2000rpm with the help of an accelerator pump. The only way to make it idle on all four would be to buy two top carbs with the idle circuit and replace the other two. The spark is not killed on the bottom two cylinders, it's all in the carbs.

[Kenny Bush]

I was told that several models have the ECU kill a cylinder or two to reduce RPMs to an idle. My V6s all have idle screws on the carbs, and they are preset(plastic caps slid over them). I have not owned a 4 cylinder 115 (yet), so I cant verify carb settup..... Come on Merc Techs....chime in here with the song/verse.......

[MurdockJr]

Sorry Bushcat I have the 115 with the 2+2 and the ecu has nothing to do with it. I'm not here to argue but if you don't know don't reply.

[DJ]

Ditto, MurdockJr.

[clanton]

All in the carbs on the 4 cylinder merc. Manual not real clear how the 2 lower cylinders get oil. The oil is mixed with the fuel before it reaches the carbs, so should be some fuel flow, unless Merc thinks it does not need oil at idle.

[The Marine Doctor]

The bottom 2 carbs still supply fuel, but not enough to fire.TMD

[BJM]

I must admit I have forgotten which 2 cylinders turn off, top or bottom. However when I adjusted the idle mixture 2 years ago (the dealer did a poor job) there were only two carbs to be adjusted. When the engine is running on muffs you can hear sharp reports as you near 2000 RPM. I get the impression its fuel building up in the exhaust and igniting once in a while. I guess it could be a trickle from the two cut cylinders building up. The reports get closer together as you near 2000. I don't like running the engine fast on the muffs so I don't really know how it sounds on all four out of the water.On my 19' Regal, it would be nice if the transition occured at 1500 RPM instead. The fastest non-planing speed is affected by the engine trying to start and stop the other cylinders, its quite annoying with all the jerking.I was really wondering if excessive idling would run it dry of oil.

[werdna]

How big a deal is it to disable the 2+2? It drives us nuts, as most of the speed limits on local waters in Aus are 8knts, but the 2+2 kicks in at about 6knts and pushes the old tub up to 10knts...CheersAndrew