Throttle high, then lower throttle and motor cuts out

[Harleyrobert4]

First, I am new to this forum and green to boating, thank you in advance for your advise.

I picked up my first boat recently, a 1979 Kingfisher tri-hull 17' bass boat with a 40 hp Mariner outboard motor.
When the boat is moving, the motor seems great, but when I first start, I must high idle for about 5 to ten min. When I go to lower the idle to put the boat in gear, the motor chokes out or I must lower the idle quickly and slam the throttle forward to stay running. When I go to try to dock the boat, it cuts out when idle goes about lower than 2000rpm. Any help you could provide would help me greatly.

I am also asking, if anyone could give me good information on this 1979 kingfisher bass boat. I have scoured the internet for information, but have come up with a blank. I have also tried to find em pictures from new condition so I can partially restore this boat, but I have found nothing on the internet regarding this.

 

[MH Hawker]

Re: Throttle high, then lower throttle and motor cuts out

Run some sea foam to clean out the carb, it may save a carb rebuild, or your sucking air some place.