Mercury Blackmax 150HP idle

[Hofty]

Folks,

So I have this 1980/1981 Mercury Blackmax 2 stroke. Recently the shop tested the stator, control box, electrical System from top to bottom. I have 2 questions:

1. The motor hesitates under load to accelerate. Below 2200-2400RPM the boat bogs down and then picks up nicely thereafter. Could this be air leak in the fuel lines? I recently changed the fuel pump diaphragm and no change.

2. Does this idle sound ok? Starts off idle around 1400RPM then drops to around 1100-1200RPM. Running on hose. In water runs the sometimes dies

Both questions makes me think perhaps the idle jets or something is blocked as it bogs down until boat gains a bit of speed then goes like snot fast.

Motor is on a 18ft fibreglass. See YouTube video link below.

 

[jimmbo]

Part of the Cowl says 1984 or 85. That was the only year the Brown Decals were used

A motor can run and sound fine running on 3 out of 6 cylinders when on the Muffs. It is a different Story once the Motor is in the water, and there is Back Pressure on the Exhaust.
Verify that you have a Strong Spark(can jump a 7/16 gap) on all cylinders. If good, then try spraying some premix into each carb, if the engine sputters, the carb was probably okay, if it speeds up, that cylinder is running lean. Also do a Compression Test to see if all Cylinders are up to snuff. A lean idle circuit can cause stumble upon Acceleration, so can an intermittent loss of Spark due to a bad wire(s), or loose/corroded connections on both the High and Low Tensions sides of the Ignition System

 

[Dukedog]

pictures without tha cowl.. sounds (terrible) like its only runnin' on "some' of tha cylinders?.. could be 'lectrical and/or carbs.. if tha "shop" gave it back ta ya runnin' like that i'd be askin' some questions?? but don't know what instructions were given to tha shop???

 

[Faztbullet]

Yes its a oldie due to clamp bracket and definitely has ignition/carb/compression issues.