mercury blackmax 150 power/wot problems

[Dukedog]

sent...........

 

[Chris1956]

Idle speed is controlled by the carb opening. The throttle cable controls that. So set it to push the cab closed and add a bit of preload.

 

[jimmbo]

Idle speed is controlled by the carb opening. The throttle cable controls that. So set it to push the cab closed and add a bit of preload.

On some of the Yamahas, but on the Merc and OMC 2 strokes, the Carbs are fully Closed, at Idle, and the Timing is used to set Idle speeds

 

[Dukedog]

chris.. with tha WH/WMH/WMV (MERC) series carbs tha only things that control idle is tha idle circuit and idle timing.. you have ta change tha idle jets ta change tha idle at carb.. tha carb openings will remain completely closed.. tha linkage has no control over idle.. if you use tha butterfly or cable to add or take away any idle control ya doin' it totally wrong.....

 

[Chris1956]

Duke is correct, and I mislead. Once you set the idle pickup timing and max spark advance, you push the throttle closed, which retards the timing, until you achieve the correct idle speed. Then set the idle stop screw to that point, and then adjust the throttle cable to push the throttle closed and add some preload.

 

[cam1399]

I verified timing and linked and synced the carbs again so I will see how it runs now

 

[cam1399]

Would the bleed valves cause the idle to be too rough to adjust idle? How can I check them to be working? I linked and synced everything and set timing but it will not idle unless I give it throttle. I checked spark and all cylinders jump 7/16 gap good

 

[Dukedog]

I verified timing and linked and synced the carbs again so I will see how it runs now

how did you verify idle timin'?.. it needs ta set with tha rig in tha water, in gear to whatever makes tha motor and you both happy.. book numbers mean nothin...

yes, tha bleed stuff can cause a temperamental idle.. both reed plate and/or cylinder bibs can sometimes fail and/or get a bit of trash in 'em.. is pretty rare that that happens though.........

 

[cam1399]

I set the timing with a light at first. After doing the initial sync. I started it on a hose in neutral to see how it ran and after a few seconds it will idle down under 500 rpm and die. Tried adjusting the idle timing to bring the rpm up but it doesn’t seem to make a difference. It won’t start back up unless I open the throttle a littler.

Which direction of the screw will bring the idle up?

 

[cam1399]

I set to 8adc idle and 21 for max timing

 

[Dukedog]

I set to 8adc idle and 21 for max timing

idles to low... bring it up ta "0" at crankin' ta start with...
"Which direction of the screw will bring the idle up?"
thinkin' clockwise.. it will let ya know for sure.....

 

[cam1399]

Okay thanks will start at 0. I may have had to way to low to make much of a difference

 

[Dukedog]

start with around 1000 rpm in neutral.. go from there.. should drop 'bout 200/225 rpm when ya go in gear.. depending on ya weight.

 

[cam1399]

Sounds good will do that tomorrow and see

 

[Faztbullet]

Older motors with some wear on em just wont set by book. Just gotta let it tell ya what it wants. Only thing I use timing lite for is WOT setting, rest is by ear and what it responds to. Leave a 1/8 gap between roller and cam and it will almost never bog out da hole. Ole Mercury feild tech rep (Roy Warrick) taught us this method.

 

[cam1399]

1/8 gap. Are you talking the roller at the bottom of your carburetor linkage? Do I set that gap before I begin the link and sync procedure?

 

[Faztbullet]

Yes at roller after sync, carbs butterflys have to be closed

 

[cam1399]

Got all that done bi was running through my bleed lines. I noticed 3 bleed lines above the bottom carburetor. The middle line was going into a nipple on the bottom carburetor. This isn’t right is it? Shouldn’t that be for the primer?

I hat a tee on top carburetor, and one nipple on top of middle carb and one nipple on bottom of carburetor. Top 2 carbs came from the primer and bottom went to the middle bleed line. That one goes to the air box right?

 

[cam1399]

 

[cam1399]