You are correct and it is probably safe. If your insurance company doesn’t have an issue, I don’t think the engines are gonna fall off or sink the boat unless of course the transom is bad. And like you say if the transom is bad, it’s bad! If you are going forward with this, recommend you look at the performance bulletins that Grady provides for the 250s versus the 300s versus the 350s. They are all available on the Grady website and in my. Experience are really pretty accurate. I think given the difference in efficiency, ie. fuel consumption, you will likely not ever recover your re-powering costs. If reliability is very important, the 300s have a long proven history and are bulletproof. The 250s were also bulletproof except for the mid. Section corrosion issues in the earlier engines. The newer 350s appeared to be very reliable, but their history is relatively short, particularly for the V6. With regard to RPMs, I know the 300s and the 250s have different gearbox ratios so the actual propeller RPM is different and requires a different sized propeller. I had to change Props when repowering to the 300s. Good luck!
