I'm just finishing a 5.7 conversion into my '88 SeaRay Seville BR. It's been a ride! Yes you'll need to extend the motor mount bunks about 4.5". It wasn't hard, if you have any fiberglass experience (google will make you an expert! LOL)... I went to the local lumber store and picked up a scrap of 8x8 pretreated lumber... then cut it to fit my extension area... then supported with a slurry of fiberglass filler, then glassed over the block to match it to the original bunks... then Gel-coated... Looks totally OEM. I've been trying to do this on the cheap... but here's the details... EFI system from a 97 Mastercraft... Cam from the same motor... Rebuilt Jasper 5.7 Roller Vortec... V8 center riser exhaust manifolds (3" version - Uggh!)... These fit right onto my existing 4.3L "Y" pipe. I'm still hoping to find a 4" exhaust manifold set... One hassle so far has been rewiring the Mastercraft plug in (they use a 5x2 flat connector configuration)... However the biggest pain for me is the "high pressure" fuel pump, pre & post filters, and return line... I finally have a workable solution in my head, and expect to complete it by July 15 or so. I did pick-up a 1.50 ratio outdrive, and will put a new impeller and seals into it before installation.
HERE"S MY QUESTION... Where should I start with proping my new 5.7L setup?
With my 185-4.3L (1.84 outdrive ratio), I used a SS 14.25" x 18 prop... Max RPM was 5100 when trimmed perfect. I tried at least 8 different props before picking that as my best overall solution (near best out of the hole, best to 20mph, near best top end).
Also, considering the extra weight and extra power... does anyone have a thought of what to expect in terms of increased performance?