150hp blackmax rich on idle

[AKNYTRO]

Hello all,
I have been researching this topic, I have seen enough similar issues posted but never a result posted.

I have had my Carbs rebuilt by a certified mercury repair center. They were also suppose to rebuild the fuel pump.They also did compression and spark test. Here is the problem boat shops will not bring your boat to the lake. I met an older gentlemen that was merc tech, he asked if they did an engine synchronization. He brought over the service manual and we proceeded to do a carb synchronization and set the Timing. I have also replaced all spark plugs.
This engine runs great mid range through top end and will idle for while until it loads up. I do not believe what it is doing is normal. However we have checked every the service manual says to check. It does not say that the idle problem would be reeds.

Reeds will they affect idle only and not top end?

Idle control box my engine does not have one but has the connectors to add it. Should I have one and will this solve the issue? I am not convinced it will.

Thermal valve in head could it be stuck in the open position injecting hot air? Would this cause it to die?

The engine loads up enough to die and then is hard to start. Any suggestions? It does also seem to run rough at idle but have been told its normal and read that it is.

Thank you for the help.

 

[Chris1956]

Can you tell us the year of the motor? A lot of those motors have 6 idle mixture adjustment screws.

Also, do you have twin engines? It kinda sounds like it.

Reeds will normally affect idle, but they are pretty robust, and don't usually cause trouble.

 

[AKNYTRO]

It is a 1992 and yes there are 6 mixture screws. Serial number is OD187885 all 6 screws have been adjusted accordingly.
just one engine.

 

[Faztbullet]

Checked the recirc valves to see if stopped up? If thermal valve was stuck shut it would run rich at low end.

 

[AKNYTRO]

Checked the recirc valves to see if stopped up? If thermal valve was stuck shut it would run rich at low end.

How would one clean them and or check them? Do I need to remove the reed block to clean them?
I may order a thermal valve and just replace it.

 

[AKNYTRO]

Anyone have any other insight. Or what you may have found on your outboard?
Or is this just “normal”

 

[Faztbullet]

Just unplug hose of thermal valve. If it idles better its stuck closed. The engine HAS to be at temp to check this and adjust carbs.

 

[Dukedog]

we proceeded to do a carb synchronization and set the Timing.

Idle control box my engine does not have one but has the connectors to add it. Should I have one and will this solve the issue? I am not convinced it will.

for idle timing you need ta do that on the water, in gear.. forget tha manual numbers.. they jus get ya in tha ball park.... set fine tunes screws as manual says.. put tha boat in tha water in gear and adjust "idle timin' screw only" to get motor ta tha rpm/speed to whatever makes both you and tha motor happy.. do this with motor trimmed level.. you can do this on tha trailer first.. after you do that you can go back and fine tunes with screws if necessary... JAN, almost ALL carbureted mercs don't like long idle periods trimmed all tha way down. (which may be your problem).. will do better at level and/or a touch positive...

forget tha little box.. better removed..