Soooo, cockpit done and no pics when we've seen every bit of this restoration? Did adding all that interior weight slow your rocket ship down?
One hell of a restoration, kudos.
Andy

I've been trying to sprint to the finish line of this 8 year, 3 month marathon, sorry. Some of the upholstery is still being worked on to perfect some wrinkles, seams, etc. I'm running the upholstery for now and will pull it in a few weeks to have it finished. I'll have photos after that is complete. :)

No, the boat gets up on plane no problem. Currently running the 5 blade 18X35X18 mercury props. I should be in the low nineties, but they slip and I'm only like 80mph at 5000rpm. I'm not sure if I need to go bigger or slightly smaller. The 4 blade 18X32X15 props we ran 85mph at 5200rpm but they vibrate so bad screws back out and the hum drives you nuts. I have some 5 blade herring 16.5X32 to try out but I bet they're not big enough.

I'm thinking you want 17.5"x30" or 17.5"x32" 4 blades, that gets your RPM back up. I tried 5 blade 17"x30" pitch Herrings on my boat and the slip was to the moon. Also did not like getting up on plane.

"Currently running the 5 blade 18X35X18 mercury props. I should be in the low nineties, but they slip and I'm only like 80mph at 5000rpm"
^^^This just doesn't sound right at 35 pitch. You should be much faster, so yes, they are slipping quite a bit, like 25%+. Try to get that slip number down to around 13-15. If those 35 pitch props grabbed, I'm thinking you wouldn't be able to pull them much past 4600-4800 RPM. this is just my experience over the past 10 years playing with those type props. Similar hull (38 CIG), surfacing drives (non-arneson)

I know what you’re saying, doesn’t make sense. RPM isn’t a problem with any props I tried so far. Blows my mind they slip so much. I can’t run a 4 bade prop because of the vibration.

This doesn't pass the smell test. you can't run "A" particular 4 blade because it's bent? Or "ANY" 4 blade? 4 blade should be symmetric and perfectly balanced. A lot more so than any 5 blade, or at least easier to dial in.

Get your hands on some different 4 blades. A high quality CNC 4 blade may be your answer. I'm sure someone on here can help you out. My backup pair need repaired or I would offer them to you to see this thing hit its potential!!!

I know you talked with Dan Archer @ Archer marine. He is an expert at dialing in these older Scarab hulls. Did you run that past him? how about Rik from Arneson? He may be able to help your application.

last message on here i have read about Rik was either he was gone from arneson
or
simply not returning calls or emails...

I’ve talked to Rik on a few different occasions about this. He understands the vibration deal with 4 blades on arneson drives. Not enough blades in the water at a time. Says 5 blades are better. My theory is the arnesons, having longer shafts and being lighter, would transfer a vibration to the hull more than a heavier shorter mercury drive. I may be dead wrong.

I talked to Dan today and he tried to buy my props lol. (Hi Dan:)) Dan thinks like you do frickstyle. The fairing buzzed (vibrated) the whole time during the 85mph run in October. I sent the props off to a reputable shop and had them balanced, had printouts of the process sent back to me. <edit-they still vibrated after that> I don’t know. Do you know any arneson rigged monohull running 4 blades?

OK - different ballgame with those Arnesons I guess. I know of a couple Top Guns up by us that run Arneson. I'll see if I can get any intel when up at the lake this weekend. What you're saying makes sense, however, by Rik's theory you shouldn't then have that much slip. 16.5" may just be too small in diameter. Unfortunately, I sold the 17"dia 5 blades I had. Try contacting Tim Johnston or Dan (ICDEDPPL) - they may have 5 blades or leftovers. (But those would be for SSM big shaft, #6 applications) Let me know if you need Tim's phone #.

I know you talk to Kelly (Payupsucker). Does he have anything you can try? Try 17.5"dia 5 blades if you can find them.

Another thing, I think it was Dan that said the 18 rake may be too much and causing the slip and I need to try 15 rake 5 blades instead. Yes, these 16.5 props are actually Kelly's, he's trying out my 4 blades, we swapped sets. Thanks for the information.