boat issue 2001 4 stroke mercury 90hp

[Kodiak]

I have done the following, cleaned carbs, replaced fuel lines, fuel filter, primer bulb assy, and plugs.

I started having issues about 3 weeks ago.

Prime the bulb boat starts right up and idles perfectly, usually can get pulled out and get to spot with no problems at all. Boat runs great at full throttle all the way out as far as you want to go.

Once at the spot fishing for awhile >20mins you can start the motor right up and then it will die after idling for 20 seconds or if you go to put it in gear and take off it will hesitate and shut off. To start the motor again you have to advance the throttle all the way and it will fire right up with some fuel smoke. Then put it to idle and it idles great and when I take off it will hesitate and then come out of it and run great again to the next spot….it does this over and over everytime you move.

I wonder why it runs so great when you first get there. And why you have to advance the throttle all the way to start the motor once it is warm.

is it the holiday station fuel??? i have always ran it with "gas" and seafoam? is the gas just not providing enough combustion to keep running after awhile sitting there cause of the gas?

[Sonicrunch]

no,it's not your fuel. But you are not getting enough fuel. Could be vapor lock.

[Kodiak]

what could be the source of the vapor lock?

[Kodiak]

if i am not getting enough fuel,,,how can it run wide open with no problems

[Sonicrunch]

Well, when you finally get it running good again, obviously you are getting fuel then. Vapor lock is an intermittent thing.

[CRFan1]

Almost sounds to me like it is way to rich on the bottom and you have either a carb or float (needle/seat) issue. The richness is why it will start when you go WOT. It also explains why it runs great for the first start of the day. A rich condition will become worse as the engine reaches operating temp and a lean condition will get better. Make sure you dont have a stuck float, etc.

[delcecchi]

Normally vapor lock comes from the motor being hot and the heat forcing fuel past the needle or something when the heat boils the gas in fuel line or carb bowl.

If it is worse on hot days that is a clue. In cars this went away pretty much with the advent of fuel injection.

You can try moving fuel lines or shielding them and the carb bowls with some form of insulation, even maybe something like aluminum foil.