Yes, If your pulling a vacuum in the fuel tank, the fuel pump cannot deliver fuel to the engine and will stall. Check the fuel tank vent hose and fitting, a common problem is wax build up in the fuel tank vent screen. If you replace the fitting, remember it is a requirement to have the screen in the fuel tank vent. Quick test is to run the boat until it stalls and remove the fill cap, listen for vacuum release.
A vacuum leak would do that. Check the base gasket under the throttle body.
Check for vacuum leak either under hood or under dash Check the operation of the vacuum operated actuators under dash Check the operation of the selector switch
Check for a vacuum leak either under the hood or under the dash Check the operation of the vacuum actuators under the dash
Loss of vacuum or vacuum leak--when engine is under load vacuum is decreased--normally you have a storage tank to compensate for this loss-however if there is a leak or engine vacuum is not sufficient the result you are seeing is normal . So check for leak either under hood or dash
Check for a vacuum leak either under the hood or under the dash Check the operation of the vacuum actuated motors under the dash Check the operation of the selector switch
My guess is you have a vacuum line problem under the hood. When the vacuum supply is cut off the system reverts to it's default position which is floor and defroster. Check under the hood for a vacuum line that is disconnected, pinched, collapsed, cracked etc. A common place for a vacuum line to disconnect would be at the vacuum reservoir. This is the black plastic ball that is attached to the under side of the hood above the brake master cylinder.
Check for a vacuum leak either under the hood or under dash Check the operation of the vacuum actuated motors under dash Check the operation of the selector switch
Acutator is a small vacuum powered motor used to open and close diverter to direct air either to defrost, floor, or vents
Check for a vacuum leak either under the hood or under the dash area Check the operation of the vacuum actuated motors under the dash area Check the operation of the selector switch
most of these door systems are vacuum controlled...but a pencil or object stuck internally can also be the cause, and not often easy to fix...for the vacuum system you can find specs and routing at the local library... check all the vacuum lines on the engine, and listen for vacuum hissing under the dash...good luck..:)
if it is automatic then this would be caused by shift down is not working in transmission
Check for a vacuum leak either under hood or under dash Check for a bad vacuum actuated motor under dash Check selector switch