Replace 351w with a 454??

Engine mounts are in a different location so the stringers would have to be modified to through bolt the mounts to the cradle. Small block motorbox will not fit over the big block. Driveshaft length may be different and you'd need a new prop. There may be some cooling line and fuel line modifications needed as well.

It's definitely not a plug and play, the motorbox and stingers are the most difficult part, the rest just costs money. Where is the engine located? What is wrong with your current engine? I may have a small block ford PCM that would work for you, and I would have interest in that big block. Email me: TRBenj@gmail.com

I'm still trying to decide what to do with my 86 Ski Nautique with a bad 351w.

   I was just offered a PCM 454 with transmission that was out of a 86 Ski Nautique.

The motor and transmission are 5-6 hours away so I haven't been able to go and take measurements. The owner doesn't know much about the boat except it ran excellent before the stringers "rotted/broke" in the hull. Unfortunately he doesn't even know the length of the boat. He's "Sure it the engine will work in my boat" but there's no way I'm taking his word for it. It's definitely can't be a simple replacement...if its even possible.

   Does anyone have any thoughts on if it's possible to replace my 351 set up with a 454 set up? I know there's definitely a size difference and weight difference.
   Is it possible to put new motor mounts in the stringers, and will there be enough room for a big block?

Just wondering if anyone has tried this? I'm going to hit a auto salvage yard to measure how long a big block 454 is compared to a .smaller 351.

Does anyone know if the Ski Nautiques with 454's were in a longer boat than one with a 351? I honestly can't imagine a big block and transmission fitting into the space where my 351 was. Maybe cutting the floor between the stringers could make room for the engine?

Hopefully I'll be making a long trip to go look at the engine set up. BTW...he sold the boat already (It had bad/broken stringers) and is motivated to sell the engine and transmission.
I just thought of something....Were the stringers damaged because of the weight or torque of a 454??????? Hmmmmmmmmm