Max hp or weight on 18

[Johnlupo]

Planning a repower this winter after we finish a complete Reno on a Classi 1976 18. Last step is to bring the transom up to 25 inches and paint. As expected My 17 yr old son is itching to put a four stroke 150Hp which weighs around 450. Based on what I’m reading I’m inclined to stay sub 400lbs and go with a 115hp. As always appreciate the feedback.