I can't give you any numbers, just a few comments/thoughts.
We bought our Islander new in 2002 with a single 250HP OX66. In Oct 2005, with 465 hrs on the OX66, we traded it in and repowered with a pair of F150s.
Our job cost a lot more than just the engines, due to replacement of single controls with dual, modifying the battery/electrical system, filling the old transom holes, and hanging two engines.
How much of your existing installation will you reuse?
- Will the F225s hang in the same holes as the HPDIs, or do they need to be further apart?
- Are you going to reuse all your control cables, or get new stuff?
- Are you happy with the current instruments, or will you want the newer Yamaha Command Link gauges?
- Do you already have fuel management, or will you want to add it.
- Do you have an NMEA 2000 network now, or are your electronics compatible and likely to be expanded?
Just some points for you to think about. If you can reuse most of your current installation, then cost is the engines, any sales tax, and the labor to remove the old, hang the new, connect and set up.
If you need to change some of the old stuff, then there would be additional costs for the materials and the labor.
I asked about the electronics and NMEA 2K because you can get NMEA 2K info from the eingines and display it on a Lowrance unit. I have lots of engine info available on the LCX-112C on the NMEA2K network.
Brian