Re: inline 6 150hp plugs?
Idle mixture may still be too lean, limiting power and making it difficult to plane. Once on plane the motor is off the idle circuit, on the main jet and runs fine.
Idle mixture must be adjusted with the boat IN the water to provide the correct exhaust back-pressure, and IN Forward gear to place load on the motor.
1 1/2 turn out from lightly seated is an initial setting to provide enough fuel to start the motor and get it into gear, from here you need to adjust each carb idle screw to "Best Idle Speed" while IN Forward gear turn one idle screw out in 1/8 turn increments or less and give the motor a minute to respond and burn off any fuel accumulated in that cyl.
LISTEN to the motor, you want to adjust to 'Best Speed' it can take a while to get to that 'Best' adjustment, finish one carb before proceeding to the next. Once finished with all carbs go back to the first carb and repeat the adjustment to be sure you have it perfected.
Now the important part
Once at 'Best Idle Speed' in gear, the motor needs additional idle fuel for crisp acceleration.
Turn each idle screw out 1/8 turn and test acceleration. Any hesitation, bog, lean cough or miss indicates a need for additional idle fuel, turn each screw out just the width of the screwdriver blade slot and repeat acceleration test.
Repeat to perfection.
Verify that you have sealed all air leaks in the fuel system.
Test by temporarily installing a clear hose between the fuel pump and carbs, run the motor and watch for any air bubbles passing thru.
Air leaking in will cause the upper carb to run low on fuel, leaning that cyl, raising combustion temp and toasting that piston.
Remember to remove the clear hose once finished with repairs.
Clear hose is not approved and is not recommended for fuel use, only as a short term testing tool.
