Mercury 150 blue water idle issues

[Newbie@boats]

Motor runs like dream at anything past idle......
I replaced spark plugs, removed the carbs and cleaned them also adjusted to floats, and replace all the fuel lines and fuel filters.

Issue is boat will start right up, idle, and then after a few minutes die out.

I played with the idle adjustment screw and either the motor idles way to high or way to low and dies out.

Compression is a solid 127 across all cylinders.

I fell like I got it dialed in, I let it run for about 10 minutes after adjusting the idle and it didn't stall, but I feel like maybe I'm missing something?

If I manaually rev the motor up it will die out but if I use the throttle control at the helm it won't it revs up beautifully, not sure if there's a timing advance or something when I use the control at the helm that makes a difference.

The worst part was idling at the boat ramp trying to get back onto the trailer when there's 15 boats around and 2 feet of water I don't have a lot of wiggle room and when the motor died out it really sucked.

Any info would be great.

BTW, before I adjusted the floats gas would come out of the bodies of the carbs now it does not.

Same idle issue as before, not sure if I am ever supposed to play with that screw or not.

 

[Dukedog]

"I played with the idle adjustment screw and either the motor idles way to high or way to low and dies out. "

which screw are ya referin' too?.. idle timin' is tha ONLY way to get idle right...then can be tweaked a little with tha screws on each carb...

 

[Newbie@boats]

It was the bigger screw below the primary pick up screw, looks like its the idle stop screw, so tonight I will readjust that lower screw and figure out if the timing is off or not and go from there......

 

[Dukedog]

these things have an "idle circuit" in tha carbs that cannot be controlled except with jetting.. didn't see year?... if yours has tha wmh or wmv's they will have a fine tune idle screw on each (initial opening is about 1 1/2 turns from closed) that can be tweaked on justa little, but don't change much....

best way ta set idle timin'......

disconnect cable, push arm up against idle stop.
check for very slight gap (paper thickness for stock motors) between roller and throttle cam... if not a gap adjust idle stop screw (1/4 20) till ya have one and loc it down.
start motor on hose with tha arm against tha stop screw adjust timin' till ya at around 1000 rpm.
adjust barrel nut on tha cable ta fit any changes made...
got to tha water and with it IN GEAR, under a load readjust (if necessary) idle timin' to "whatever makes you and tha motor happy"... don't worry 'bout what book "suggest"......

 

[Newbie@boats]

I will check the timing tonight, been reading about it today, just got to stop and grab a timing light and will re ad-just that screw as well

 

[Newbie@boats]

Update:unscrewed that screw I was adjusting last night, checked the timing with the throttle all the way down and it was WAY off, like 2 before TDC, so on my motor the sticker says WOT 20* BTD and 4 ATDC I adjusted the WOT and the idle to exactly where it needs to be and the motor idles beautifully, not to high not to low just perfect. Next time I'm out on the lake I'll bring the timing light and tools just in case I need to tweak it a little bit.

Much much easier than I anticipated, took me longer to go buy a timing light then it did to time it. Thanks for the help

 

[Chris1956]

OK, glad you have it working. For your info, idle pickup timing is set when the carbs are still closed, but ready to open. It should be 4* ATDC. The throttle is usually retarded from idle pickup to achieve idle speed, retarding the spark timing.