I have a 1985 Mercury Black Max 150 HP that bogs down when i give it throttle.I drove it around the lake twice , was head back in when it turn off .Turn it on and it started to bog down . I had the same problem 2013 and had the carburetor and diaphragm rebuilt and work fine .It start up fine with the flusher earmuff but at the lake it will bog down when i give it throttle . I have put new spark plugs , diaphragm , stator and tigger . What could be causing this it to bog down ?

Due to the motors age the first thing I would check is compression.

How old is the fuel supply hose and primer bulb?

What is the age of gas in your fuel tank? Is gas treated with conditioner?

When was last time fuel filter was changed?

I agree with Tbird.. Trash in carb.. gotta figure out how it got there

Carbs and check value got need replaced also

Clogged fuel lines from ethanol gas. I had the exact same issue. Idles just fine, dies at throttle up.

I had a 1985 175 Black Max and went through this from time to time. Always the carbs. I replaced all of my fuel lines with ethanol resistant ones. Replace needles and seats and clean the carbs. I probably replaced mine 5 or 6 times over 30 years I owned it. Once I got bad ones. Drove my mechanic nuts trying to figure it out. I had one mechanic tell me to remove the plugs on the bottom of the bowls and spray it out with Berryman,s. Mine had red thread sealer on them so I never tried it. Check your floats for leaks. I had one with a pin hole one once. Also make sure your floats are adjusted correctly. A high float or 2 will cause the motor to bog.