Issue getting on plane and engine turning off under load.

[jetboatperformance]

Would tend to agree with Menace and others re the potential Carb issue , most commonly the accelerator pump circuit could be a problem (cough and die out) , Quadrajets were OEM Carbs in Gm products from late 60s to mid 80's and can actually work well with stock applications (I actually worked on these at Cadillac ) . The fact that this boat sat for 2 years is a complicating factor as modern fuels have a very short "shelf life" and they also tend to attract and moisture .moisture can over time gather in the low reaches of the float and accelerator pump well (inside the carb) and create white powdery corrosion which reeks havoc with carb internals Very likley you may have to clean and kit the carb as a starting point Tom