Mercury Blackmax 150 hp boggs out when in gear and trying to accelerate

[faztbullet]

The engine actually is designed to run 3 cylinders at low throttle (no wake speed), and then engages the other 3 when you want to get on plane. Your other 3 cylinders aren't firing, thus the low speed

Mercury has never designed or made a V-6 outboard that operated this way. Your problem was a bias circuit bad in switchbox, if you didnt replace as them as a pair it will fail again. Sorry

 

[racerone]

Anymore wisdom from ---bredniakr ?

 

[Calhoun!]

So I have an 89 merc xr2 150 black max with the same issue I think. Was on the lake yesterday and coming up on plain running perfect it just bogged to a stop and continued to idle but I could hear a miss in the engine. In neutral I can rev it but put in gear and it dies. I got it home and checked compression and it’s at 100-105 on all 6 cylinders. Checked spark and that seems fine. Carbs were rebuilt in the spring ( three months ago ) new fuel lines, new vacuum lines, the stator was replaced last year. Switch boxes were replaced two years ago. This old Shadow 180v has been running like a champ. It’s like someone flipped a switch and said nope not today! Any idea where to go from here? Did you fix yours?

 

[brokendiesel]

So I have an 89 merc xr2 150 black max with the same issue I think. Was on the lake yesterday and coming up on plain running perfect it just bogged to a stop and continued to idle but I could hear a miss in the engine. In neutral I can rev it but put in gear and it dies. I got it home and checked compression and it’s at 100-105 on all 6 cylinders. Checked spark and that seems fine. Carbs were rebuilt in the spring ( three months ago ) new fuel lines, new vacuum lines, the stator was replaced last year. Switch boxes were replaced two years ago. This old Shadow 180v has been running like a champ. It’s like someone flipped a switch and said nope not today! Any idea where to go from here? Did you fix yours?

I know this is an old post here but any chance you figure out this issue. I'm having what's sounds like the exact same problem. Was running great then just said nope, bogged down cant rev in gear with power. It'll run just really bad and not accelerate. Will idle all day can rev without being in gear. I'm going crazy over this thing.