2001 115 merc 3rd & 4th cyl cuting in & out

[Stevenhj]

On My 115 the top end cylinders don't cut in smoothly. They stumble in and out anywhere from 2200 to 2800 RPM. It runs great below 2200 on two cylinders and great above 3000 rpm on all four but cuts in and out in between. What type of adjustment does it take to fix this?<br /><br />Steve

 

[Laddies]

Re: 2001 115 merc 3rd & 4th cyl cuting in & out

Ck the timing and carb pick up

 

[WillyBWright]

Re: 2001 115 merc 3rd & 4th cyl cuting in & out

That's what those motors do. That's what makes them so unpopular with waterskiers. At barely-planing speeds, you can't get a constant speed. It runs on the upper two until about 1800rpm, and on all 4 above 2200rpm. (Those are ballpark rpms.) Inbetween they have a hard time deciding on whether they should run on 2, 3 or 4 cylinders. Short of redesigning or replacing the motor, there isn't a damn thing you, me, or anybody can do about it.

 

[daza1]

Re: 2001 115 merc 3rd & 4th cyl cuting in & out

Gidday SHJ i have one of these motors, 2004 and just taken in for its 20 hr service, the motor surges as you say between 25-3000 revs which but should be 18-2200 revs as far as i no..The sales man rekoned 18-22 & is surprised as is the mechanic. They are taking it in the next few days to see what the story is..<br />It,s a pain in the *** when your in a choppy sea and you want to sit on 2500-3000revs for a comfortable ride and constantly have to adjust the throttle.<br />I,ll let you no what the outcome is if you like.,i,m hoping for some sort of resolution,but i,m not holding my breath.

 

[emzle]

Re: 2001 115 merc 3rd & 4th cyl cuting in & out

I agree, this motor is painful. I have never had a good idle from mine(02 model), and now am troubleshooting no spark on 1 and 2 (low rpm cyl)<br />Would appreciate any info you guys can pass along.

 

[imported_JD__]

Re: 2001 115 merc 3rd & 4th cyl cuting in & out

I have owned (passed tense)two of these engines and experienced all of the above. One thing that will help to smooth out the idle is to make sure the engine is level and not trimmed all the way down/tucked.<br />When you're coming off plane, level the engine and hold the throttle just under 1800 RPM for a few seconds before dropping back to idle speed.

 

[daza1]

Re: 2001 115 merc 3rd & 4th cyl cuting in & out

Got the boat back 2day, still the same.. took it out on the way home, and still the same..........<br />They,re gonna try replacing jets in carbs from another model to see if it makes a difference.From what i,ve heard it,s not so common and most of these motors DO cut in and out between 1800-2200 revs, and that mine is rare for cutting in and out between 25-3000.<br />ANY INFO???????????

 

[SeaKaye12]

Re: 2001 115 merc 3rd & 4th cyl cuting in & out

Hi,<br /><br />Could one or more of you please take the time to explain how these 2+2's work?<br /><br />What causes the high speed cylinders to fire or not fire?<br /><br />Is it ignition depravation or fuel depravation?<br /><br />I would assume ignition depravation; because if there was no fuel supplied; there would be lubrication issues; wouldn't there?<br /><br />On the other hand, if fuel was available and there was spark depravation, where would all the fuel that''s being sucked through go (below 1800) when those two cylinders weren't firing?<br /><br />If you could point me to another thread that explains all this..or explain it here...I'm interested to learn more.<br /><br />As far as changing things? Is that possible? Can these engines be re-worked so all four cylinders fire all the time? <br /><br />Thanks for reading, Chuck

 

[Boatin Bob]

Re: 2001 115 merc 3rd & 4th cyl cuting in & out

As far as I know it's done through fuel depravation. The carbs for those 2 cyls don't have a low speed circuit but apparently there is just enough fuel that goes through to give it lubrication but not enough to actually generate any combustion worth mentioning. I've asked the same question before but never found anyone that had done it. The obvious piece is to change the 2 carbs but not sure what happens with timing? Others have said it will idle even rougher with all 4 firing.