125 Merc 2+2 No speed between 7-19 mph?

[tomfsu]

I bought my boat recently and have a 2001 Mercury 125 with the 2+2 carb system. When I accelerate I can go to around 6 mph and then it kicks into the other 2 carbs and it pushes the boat to around 20 mph. I dont seem to have an in between speed. Any ideas what this could be? I know these 2+2 systems are unique but is this normal?

As a note, I believe I have a fuel delivery problem because the boat is boggin down at certain times when I am around 4000 rpms. Though I imagine this is a whole different issue.

 

[twostroke87]

Re: 125 Merc 2+2 No speed between 7-19 mph?

All of the 2+2 engines are like that, there isn't really an in between speed, its just something you will have to learn to deal with.

As for the bogging down at high speed, it is most likely a fuel problem due to that the carbs are constantly being used and not being used, so the fuel has more time to sit and gum up small jets.

 

[CharlieB]

Re: 125 Merc 2+2 No speed between 7-19 mph?

Excuse me?

The lower two carbs do not have an idle circuit.

But that is where the difference ends.

They do have the transition circuit holes that are exposed as soon as the throttle plate moves, and allow fuel to pass, and that cylinder begins to work.

I suspect your carb linkage needs a very careful link and sync.

Also pay close attention to the accelerator pump adjustment, it provides an addition shot of fuel to the lower cyl's to assist on any rapid throttle movement off an idle.

Once adjusted correctly it will be very hard to detect the transition from 2 to 4 cyl's.

 

[tomfsu]

Re: 125 Merc 2+2 No speed between 7-19 mph?

O.k, I spoke with my boat mechanic and he mentioned that this is normal with the 2+2 system.

I am still confused, is he misinformed or is that the truth?

 

[CharlieB]

Re: 125 Merc 2+2 No speed between 7-19 mph?

I run an small independent repair service.

I also have a 96 Mariner 115 (2+2) on my ProCraft V180C

Like I said earlier, you'd be hard pressed to tell when the bottom cyl's come on.

It's all in the carb synch and accelerator pump adjustments.

Of course the carbs must be squeeky clean and the top two idle mixture adjustment must be done in gear in the water PLUS almost an 1/8 turn out, just enough to remove any hesitation or bog when the throttle is slammed WOT from an idle in gear.

 

[tomfsu]

Re: 125 Merc 2+2 No speed between 7-19 mph?

Thanks Charlie, I guess I will be making the adjustments on my own or looking for another mechanic.

 

[bowman316]

Re: 125 Merc 2+2 No speed between 7-19 mph?

are you sure it is just not an issue of being on plane or not?
below 19 i guess you can not stay on plane, and then you will drop to around 6 knts. But there is that noticable pick up when first getting on plane on every boat. I mean, i can't go 10mph, it is either 6 or 17, no real inbetween, just because of the water resistance.

 

[tomfsu]

Re: 125 Merc 2+2 No speed between 7-19 mph?

You bring up a great point about being on plane. Thanks, that may be it.