Idle problem

[fishinwrench]

That's not too bad actually, but I'm blown away that they went to all the trouble of disassembling the carbs but didn't replace the needle valves....only the gaskets. The part number they list is only a gasket set and NOT a complete carb kit.  There is a very good chance that the carbs will have to be torn apart again to refresh the needle valves and set float levels correctly since they obviously didn't do that.   The "bulb squeeze test" will tell us if that needs to be addressed, and I'm pretty sure it will.

The CDI being hooked up wrong is a mystery, you'd have to be drunk and totally color blind to make that mistake.  But who knows?  And rectifying that shouldn't result in additional charges, I mean lets be real it only took him 5 seconds to re-match the colors.

The ignition system is actually designed around Champion spark plugs but I've never seen any problems caused by using the proper NGK plugs in Mercs.     The NGK crossover will always be a little hotter plug which is kinda good for Mercs with their lower low-range torque (may help the hole shot some).  So I'd stay with the NGK.

You don't want to put fresh plugs in BEFORE taking it to a tech because being able to "read the plugs" helps a tech diagnose running problems.  When you throw fresh plugs in it makes it harder to determine which cylinders are running differently.

[Stump bumper]

Thanks Fishinwrentch, will get hooked up as soon as I can, worked just called and I am on the road tomorrow, will get it hooked up this afternoon if I can if not won't be home for a week.

[Stump bumper]

Alright, screw the 2 idle mixture screws in until they seat and then tell me how far out they were set.  (number of 1/2 turns).  

Turn them back out 1 1/2 turns and fire the motor up on muffs.   Once warmed up depress the accelerator pump plunger a few times with a screwdriver (it is mounted on the port side of the powerhead)  and tell me how the motor reacts to that (no change, or RPM's pick up momentarily....or does it stumble and act like it wants to die?). 

Then while it is idling squeeze the primer bulb fairly hard and hold it depressed for a few seconds.  Any change in idle speed ?   If no change then push in the key (primer) for about 3 seconds and tell me if RPM's increase or decrease.

If I know all of the above I can probably tell you what needs to be done to rectify the issue.

Ok, the top screw was out 8 (1/2) turns bottom out 6 (1/2) turns, took them to 1 1/2 could not engine to idle without advancing gas. Took both out one full turn and it idle to warming up. Depressed accelerator pump plunger several times no change in RPMS. Bumped up primer bulb (it was hard before starting was soft while engine was running) no change in RPMs or how engine idled. 

Sounded good on muffs, was idling better, but not smooth I know once the blade is in water to expect that to change.

Very interested in what you have to say or if what I have reported makes any sense.

  

[fishinwrench]

Either your float level settings are off or the fuel quality is bad,  and the accelerator pump diaphram is bad or its hoses/fittings are blocked.    

[Stump bumper]

Either your float level settings are off or the fuel quality is bad,  and the accelerator pump diaphram is bad or its hoses/fittings are blocked.    

It runs fine when not at idle. jumps on plane quickly and runs good wide open. A bad accelerator pump diaphragm would not affect the engine at higher RPMS? I have no idea that is why I am asking.

I will try a higher octane, ethanol free fuel next time out.  

[J-Doc]

Check for any sticky linkages yet?? :-)

[fishinwrench]

The accelerator pump only gives a shot of fuel to the lower 2 cylinders during a hole shot.  Squirting it during idle like I had you do SHOULD make the RPM's jump up a bit....and you said there was "no change".  If it is accelerating fine in the water then it may be adequate, but if it was me I would service it anyway, it may be partially blocked oror possibly leaking through.

If you can't smooth out the idle with the mixture screws then SOMETHING ain't right.  It should maintain a smooth idle with the mixture screws 1.5 to 2 turns out, so I'm banking on a problem with the accelerator pump (easy to check and fix) and/or improper float settings.  

Assuming of course that the fuel is fresh and of decent quality.

 

Jdoc,  Mercs trigger has tons of tolerance (unlike Johnson/Evinrude) so it's doubtful that it is hanging up.

[Stump bumper]

Thanks fishinwrench, I will diffidently change the accelerator pump, I am guessing it is a rebuild kit, looks easy enough to get to.

When I say the idle is not smooth, the RPMS are steady but the engine shakes alot and sounds like it might die, sort of like a misfire but stops when given more fuel so I am thinking air is getting in where it does not belong or fuel is not flowing right. Since I have no idea how to set the floats I will start with the easiest fix and work my way up.

Yes JDoc did check the movement of all the linkage and everything seems to be good. Maybe we can run into each other at the ramp some day and you take a quick look for me and give me some tips.

Thanks again for all the free advice, feels like I have real friends here.

 

[fishinwrench]

We're all friends here, NP.

Don't forget to check the hoses and nipples associated with the accelerator pump, they become gummed up and clogged when the engine sits awhile.   If it is pumping fuel like it's supposed to, and not leaking through constantly, then you'll notice the difference when you depress the plunger.    

Those motors were designed as "fuel efficient" by idling and running below  2800 rpm on the top 2 cylinders then kicking in the bottom 2 upon higher demands.   They are pretty finicky so if everything isn't just so.....they run like crap.  I had one exactly like yours once that I had a hell of a time getting to run right, and it ended up being a leaky primer solenoid that was oozing fuel all the time, but yours passed the hard bulb squeeze test so it probably isn't that.  I bet yours isn't gonna run 100% right until those float levels are reset.   If that shop didn't replace the needles then I bet a dollar they paid NO attention to the float level setting.