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Mariner 2+2 accelerator pump troubleshooting

T

tooltime

New member
Good Morning,
Looking for some guidence. I am trying to troubleshoot an issue my my mariner 2+2. when I have it in idle or in low forward gear and take a screwdriver and push plunge down on accelerator pump I do not hear cylinders 3+4 coming on line and reving like I used to.

When wot in water I am pushing close to 5000 Rpms so I assume that 3+4 are on at that point and working properly .

Idle seems slightly high on muffs in driveway and haven't had time to put in water yet but always under impression when hitting the accelerator pump the engine should rev. What could cause it to not be reving. I always new a good test was to depress the pump plunge and you hear the cylinders fire up


Carbs cleaned and rebuilt last year

Thanks
Tommy
 
I have an 03 Merc 115 HP 2+2 engine. It only runs on the top 2 cylinders up to 1800 RPM because the bottom 2 carbs lack idle screw jets. I don't know if pushing the accell. pump makes the bottom 2 cyls. fire or not. Does the engine hesitate when you give it a quick throttle or does it act normal? You could check the accel. pump just by watching the output nipple w/engine off.
 
yeah, I feel like it used to rev the 3+4. Under the 1800 it is only running on top two cyl. As you throttle up, the throttle arm hits the accelerator pump and squirts fuel into 3+4 and brings them online. If you manually hit the pump, it should do the same thing and rev when they light up.

I guess I could try pulls the bottom plugs when running and see if the engine changes to confirm if they are running even under the 1800.
 
I did a search about troubleshooting the accelerator pump on the 2+2 engine and found this thread. Using a screwdriver is a great idea to test the function. I tried it yesterday as I was going through my annual first of summer boat cleanup and maintenance. It worked! I had my engine idling on ear muffs in the driveway. When I depressed the pump plunger the bottom cyls did appear to fire as the rpms jumped up with a roar.

One thing I did notice is that the bottom cyls did not fire until the plunger was fully depressed as if the throttle was bought to WOT. I thought the bottoms should have fired with only half that plunger amount. I wonder if there is a way to increase the amount of gas being squirted? I'm wondering if there is a way to changing the timing of the squirt? I think the gas should squirt in way before WOT.
 
The accelerator pumps ARE NOT not squirting at WOT. They are working at around 1800 rpm because the bottom 2 cylinders need the extra shot of fuel to start the process. These are not a motor you want to learn how to make adjustments. They are very easy to screw up and very hard to get back to where it runs right. It sounds like you think you have a problem that doesn't exist. Most outboards will idle high on muffs that is normal.
 
At idle the throttle is barely open...I don't think that any addition of fuel from the accelerator pump should cause any great difference in RPM...it would seem to cause an over rich condition and possibly a drop in RPM
 
bobbyc said:
At idle the throttle is barely open...I don't think that any addition of fuel from the accelerator pump should cause any great difference in RPM...it would seem to cause an over rich condition and possibly a drop in RPM
Click to expand...
On the 2+2 motors the bottom cylinders are starved of fuel because the bottom 2 carbs have no idle circuit in them. The bottom 2 carbs provide only enough fuel mix to provide lubrication not enough for combustion. Since the spark plugs on all 4 cylinders always fire and the bottom 2 carbs have the accelerator pumps. When you hit the pump it provides enough fuel to have combustion.
 
Yep, it's the accelerator pump to the bottom two cyls that helps to get them firing when you throttle up. The bottom cyls have to be transitioned from not firing because of not enough fuel to a firing state with plenty of fuel. It's the accelerator pump that does it.
 
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