Boat runs on land but not when launching in water

Assuming it turns over and you have spark...water in the fuel tank which gets picked up when level in the water but not when canted on the trailer?

 

Allergic to water ?

 

I’m with @Garintheair its a fuel problem
Dont trust boat fuel gauges either
If low add more gas

 

idle to low, carb improperly adjusted.

 

I'd put wheels on it and drive it around town.

 

I like the funny ideas, but lets try this, “did not run, kept dying” < define. At idle, at a certain rpm, on plane, when cold, when warm, when the mother-in-law is aboard? Need more details.

 

Could be a fuel filter with debris that blocks the flow when at the decline of the ramp, but allows flow when on level land. Everything to me points to a fuel problem.