74 aquasport 196 - 84 blackmax 150hp idle problem

[luv2flycessna]

anyone help me out with my 84 150 hp blackmax it idles rough, get on it and it takes off quick runs smooth as can be and gets up to 41 mph with it comes back to idle its  rough sometimes stalls when going from forward to reverse but not often, when it does stall it fires right up but is rough, when the engine is cold fires right up also no problem but rough, any help would be appreciated. Thanks (btw my first boat)

[GoneFission]

If it does OK at high speeds, it's probably carb related.  You may need to clean the idle jets or the idle may be set incorrectly.  This could also be a timing issue - Mercury V6 engines have a somewhat complex timing arrangement.  

I would probably start with carb overhaul.  It's not hard to do and will probably fix the problem.  If not, then you are looking into possible ignition problems - maybe stator, coil or two, or switchbox - you should take it to a Mercury service center with the equipment to troubleshoot the Thunderbolt ignition system.  You can't do this correctly without the right test equipment.  

Good luck!