75 Mercury runs great wot - poor at lower speeds

[HenryAvery]

It is an '86 75hp on a 24' pontoon. Must be choked and idled up to start. Runs poorly at anything less than 3/4 throttle but runs great wot.

Continuously pushing the choke on and off keeps it running (poorly) at lower speed so I could bring it in to dock.

Last spring the carbs were rebuilt and it got a new fuel pump and ran great all last summer.

Ideas? Please help.

Thanks

 

[asm_]

Re: 75 Mercury runs great wot - poor at lower speeds

List of things to try.

1. tune the idle needle as per service manual
2. perform link&sync to ensure timing is correct at idle.

B

 

[HenryAvery]

Re: 75 Mercury runs great wot - poor at lower speeds

Thanks for the reply. I'll give it a try.

 

[Wingedwheel]

Re: 75 Mercury runs great wot - poor at lower speeds

Could it be a vacuum line?

 

[HenryAvery]

Re: 75 Mercury runs great wot - poor at lower speeds

The top carb was running too lean. I backed the idle mixture screw out almost half a turn and it is running great now.

Thanks for all the suggestions.