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2009 Merc 4 stroke 20hp--engine bogs at half throttle and above--otherwise runs perfect

C

charlie_D

New member
I have this Merc that is seemingly unfixable. The unit bogs once I get about half throttle and above. I have the service manual and have checked everything for proper pressures in the fuel system and its related parts. I have had the carburetor ultrasonic cleaned...I have replace plugs....verified proper resistance values throughout the electrical system and related parts. I have made sure all of my hose fittings are good and tight....my next thought is the CD unit. From what I can tell, is that this unit automatically adjusts the timing of the engine during throttle up and throttle down.... IS there ANY way to have that CD unit checked out to see if it is any good before I go and throw a couple of hundred bucks into a new one...only maybe to find that was not the problem at all? OR what else should I be looking for?

The unit starts like a champ..idles perfectly...evens revs up to a higher speed when I have it in a huge barrel of water....but when I take it to the lake and give it the gas....it decides it going to bog at half throttle and above

I have not checked the unit out with a timing light as of yet.

I am completely open to suggestions...thank you!

Its a model 1F20201HK Serial: 0R298622
 
Not Familiar with the 4 strokes - so take my suggestions as such. Just trying to help here.....

There is a "Trigger" plate on my 2 cycle under the flywheel that "times" the firing. IT is possible to ohm out and and do a DVA max voltage test. Same with the 2 stroke stator.

However, It almost sounds like it's bogging down between low speed jet and high speed jet handoff. Ther may be a an accelerator pumper? or "welch plug" reservoir that's either plugged or mal functioning. Be sure all levers and pivots on the carb are connected to something properly. Also, the low speed jets may be plugged or slightly need to be opened. JMO
 
Thank you for responding Canu....Trigger plate, this unit does not have one....I did replace the accelerator pump..yes, that was on thing I forgot to mention in my original post....You are correct, it does act like it is bogging down between low and high speed jet handoff...that is exactly where my original thoughts were aimed..

Upon further digging, according to Mercury, the only 5 reasons I would loose my higher rpms...are
1) Low oil pressure
2) Ignition charge coil
3) Ignition high coil tension leads
4) CD unit
5) Spark plugs

I would care to add a #6 which would be the carb needs a cleaning and or accelerator pump

I also pulled the oil pump, took it apart and checked the seals and measured the maximum range space tolerances allowed within the pieces that make up the pump unit. All were perfect. All of the static resistances on the 1 - 5 list above (if there were any to measure), were in the acceptable range.

The only thing I haven't tested and do not know how to test is the CD unit. Is there someplace anyone might know of as to where to send it for testing OR is there some way I can test it?

I very much appreciate your help....

cd
 
Canufixit said:
Not Familiar with the 4 strokes - so take my suggestions as such. Just trying to help here.....

There is a "Trigger" plate on my 2 cycle under the flywheel that "times" the firing. IT is possible to ohm out and and do a DVA max voltage test. Same with the 2 stroke stator.

However, It almost sounds like it's bogging down between low speed jet and high speed jet handoff. Ther may be a an accelerator pumper? or "welch plug" reservoir that's either plugged or mal functioning. Be sure all levers and pivots on the carb are connected to something properly. Also, the low speed jets may be plugged or slightly need to be opened. JMO
Click to expand...



Hi Canu...thank you for responding....I do not find a trigger plate on this motor... I did replace the accelerator pump...I forgot to mention that in the original post. I will try opening the low speed jet a bit at a time and see what happens...right now it is at 1 3/4 turns open...thank you for the suggestions! I will keep you posted as to what I find out..

Originally when I took the carb apart for cleaning, I forgot to FIRST turn in the low speed to see where it was set... Since then, I have read to start at 1 1/2 turns all the way to 3 and 3 1/2 turns, then fine tune it from there....neither start setting has seemed to help....and the service manual doesn't tell you.

CD
 
I checked the parts breakdown on the 4 stroke carbs. My inputs;

- I see no "accelerator pump" - did you mean fuel pump?

- You had your carb apart - are you SURE you have the correct main nozzle (pick up tube?) and high speed jet ? There are multiple parts/ numbers for different hp/applications.

- The Main nozzle (pick up tube?) (Pressed in?) - is it installed in the correct height?? IT may be bottoming out on the high speed jet and or fuel bowl and starving fuel on high speed start up.

- Years ago I worked on what I believe were similar carbs on small engines. On the Carbs there was a small (3/8"?) hole bored in the side of the card - that had a freeze plug like disk pressed onto/into the top to seal it off. The was called the "Welch" plug. Behind it was a small storage cavity area for fuel to collect so it could spit into the carb on high acceleration. This was designed as a crude type of "accelerator" pump. There were tiny holes in the bored hole that filled and dumped the fuel during acceleration. Sometimes crap would fill the cavity and block the holes. If it's not clean / clear - it will cause the issues you describe. Advise if this is so and I'll tell you how to clean.

Hope that helps!
 
It's called an accelerator pump,. the exploded view parts lists it as a "plunger" ......... and the welch plug area you refer to is where there is now called a "pilot screw"...It's an air/fuel screw adjustment....This setting has never been clear to me....as the service manual does not state a rough start setting point...and of course, I removed the screw for cleaning BEFORE I checked to see where it was currently at. I have read to start at 1 turn, 1 1/4 turns, 1 1/2 turns, 3 turns, 3 1/2 turns....I have tried the 1 1/2 turns and the 3 turns as a starting point, then tweaking it from there to get smooth idle, in either way, I still get bogging at half throttle and above.


The jets...there are two of them, one screws in until it is snug, then screw a cap over it...the other just drops in and is covered with a screw in cap...there are different jets for the 15 and 20hp unit....I did recheck, mine are showing for the 20hp


I sure do appreciate your insights and help....I've had this thing in for fixing/cleaning almost every year...I wonder when I should just go buy another new different brand motor and stop dumping money in this thing. These past three years, the boat has sat in the garage after I have, each year, picked to boat up from the service shop...they say its roaring to go...I get to the lake...cant get it past half throttle...back to the garage it goes til the following year. If I take it back, they say I ran bad gas...will add a bunch of new parts, charge me tons of money for labor...and tell me its roaring to go...do I sound like I'm giving up hope for this unit?

Again, thank you for your time and thoughts!

CD
 
charlie_D said:
It's called an accelerator pump,. the exploded view parts lists it as a "plunger" ......... and the welch plug area you refer to is where there is now called a "pilot screw"...It's an air/fuel screw adjustment....This setting has never been clear to me....as the service manual does not state a rough start setting point...and of course, I removed the screw for cleaning BEFORE I checked to see where it was currently at. I have read to start at 1 turn, 1 1/4 turns, 1 1/2 turns, 3 turns, 3 1/2 turns....I have tried the 1 1/2 turns and the 3 turns as a starting point, then tweaking it from there to get smooth idle, in either way, I still get bogging at half throttle and above.


The jets...there are two of them, one screws in until it is snug, then screw a cap over it...the other just drops in and is covered with a screw in cap...there are different jets for the 15 and 20hp unit....I did recheck, mine are showing for the 20hp


I sure do appreciate your insights and help....I've had this thing in for fixing/cleaning almost every year...I wonder when I should just go buy another new different brand motor and stop dumping money in this thing. These past three years, the boat has sat in the garage after I have, each year, picked to boat up from the service shop...they say its roaring to go...I get to the lake...cant get it past half throttle...back to the garage it goes til the following year. If I take it back, they say I ran bad gas...will add a bunch of new parts, charge me tons of money for labor...and tell me its roaring to go...do I sound like I'm giving up hope for this unit?

Again, thank you for your time and thoughts!

I have a 2008 with the EXACT same problem, even the difference between running in the barrel Vera the lake! I am very interested to see how you fixed it.
Click to expand...
 
I have a 2008 with the EXACT same problem, even the difference between running in the barrel Vera the lake! I am very interested to see how you fixed it.
 
I will keep you all informed....as to what it takes.... i did bite the bullet and order a new cd unit tonite....I will say it is the last dollor going into that thing. After this, it's either Honda or Yamaha
 
UPDATE...I apologize for not responding sooner...this is what fixed my problem

1 can of Mercury PowerTune used as directed. I used the whole can (which is what Mercury support said to use)...it also says that on the label directions.

The motor had carboned up and the oil rings had become unseated enough to cause compression loss...

Mercury support said "this is common in all of their 4 strokes" and that I should use their "Quickleen gas additive to help keep that from happening again"

Runs like a new engine!!
 
I should also state a couple of things that I noticed early on that should have been "tip-offs" to me that indicates a possible ring/compression issue..

1) I could notice a light smell of fuel to some degree in the crankcase when I took off the oil filler cap and took a whiff

2) Just before the the engine went into its "half throttle mode", I felt like the motor wasn't quite as fast on the water as it used to be
 
One more thing... Mercury support said it was almost impossible to do a reliable compression check on the cylinders because of the way one of valves is held partially open to allow for easier starting....ONLY a leak-down test would work for troubleshooting purposes
 
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