Boat motor dies after throttling down?

Question

my father has a mercury 40 hp 4 stroke its pretty much brand new. its on a pontoon boat...but anyways heres the problem, every time he uses it at higher rpms it workd great but its when he throttles down to low rpms or idle it shuts off almost every time. it starts right back up though without hesitation. any good info would be very helpful. also i know it has three carbs if that helps any

Answer 1

I agree with Mr. fixit.  But, before you do that. I'm guessing that you have remote controls on this engine.  If so, disconnect the throttle cable and run the engine by hand.  If it dies as it has been doing, first turn the idle stop s***w in  a turn or two.   then watch the carb linkage.... it should be in sync.  Then turn the connector on the end of the cable so that it snaps on without moving the throttle cam.  Now try it again.  Good luck.

Answer 2

You have a problem with your carb set-up.On this type of engine the carbs must be synchronized with a carb tuner.You will need to have this done at a marina,as I suspect you do not have a carb tuner at home.It should not cost that much for

you to have this done.Adjusting the idle screws on the carbs alone will not fix your problem because they also need to be in sync. with each other.Hope this helps and good luck.