a.altman

First off, I'm a little new to the real hp boating world. With that stated, I just bought a 38ZR w/twin 700sci. It had Merc 5b cleavers (17x37"). Was blowing out heavily while trying to plane. It turns out the props are only 16.75" and were ground down. At 80 slip was like 24%. Found a good deal on 6b Herings (17x37). These too blowout but much better and slip is down to about 16%. However, now she feels a little loose over 80 and worse as you go faster. I imagine stern lift is now the problem. I also imagine the high x-dim is causing the blowout. So my question is, does anyone have advice or combinations of props/spacers that work to minimize blowout and keep or improve top end speed/stability? Also, this winter I'm going to do a Whipple stage 3 or 4 upgrade. This should add another 165hp to 210hp (per Whipple).

Apexwarrior

Those are 700's with NXT drives? Some slip out of the hole is not surprising and I think just the way it is with that setup.. You have to manage those sticks.

I suggest you first figure out the power situation and then give Brett at Bblades a call to discuss. They have a prop testing program that you may want to use once you get the power set up.

a.altman

They are NXT drives. I walk it out the hole and maintenance around 2800 until she climbs up and bites. For some reason the starboard side begins slipping first, so it takes a little back and forth with both sides. I actually did speak with someone at BBlades and have begun to question their advice. What seemed odd was the suggestion to try to tweak the 6b props to eliminate the loose feeling. He suggested, as a test, swap the right/left prop and test drive using reverse as drive. Maybe I'm wrong but that doesn't seem right. Also, I've read that going with an outer rotation will reduce performance. Not the direction I want to go. Maybe I need to talk with Bret at BBlades.

Apexwarrior

Turning in usually gives you 1-3 mph on the top end and sucks the stern down. Turning out will lift the stern and make it easier to maneuver around the docks. Having gone through the in vs. out thing last summer myself, I went back to how the factory set it up, turning out. The extra few mph were rarely used, but I missed the dockability every day.

I've had great experiences with bblades as have many on this board. I'd be surprised if they steered you in the wrong direction and between them and the factory, I dont know how to get better advice. Bottom line is this will take lots of testing to figure out. Switching right to left is the first and easiest step.

a.altman

What I've read confirms what you stated about rotating out gives stern lift. That's why i didn't understand why I would switch to rotate out to combat the boat feeling loose with the 6b prop. It seems counter intuitive to add more stern lift to resolve the excess stern lift created by the 6b prop. As for BBlades advice, they do seem to have a great reputation but i think I need to work the issues out with Bret himself.

tnc110

This could be totally wrong...but from what I have read, Donzi water tested every boat and sent them out with pretty good settups from the factory. Might call them, who knows what info you will get with new ownership though. Maybe call Josh at DonziDirect???

If you are going to add 300-400 hp, why waste your time tying to tune now....wait til you are done. Keep us updated...I would really like to see what a ZR can do with 1800hp.

a.altman

Thanks for the advice. Point taken with the horsepower change. I'll keep posting.[ATTACH=CONFIG]511647[/ATTACH]

a.altman

[ATTACH=CONFIG]511648[/ATTACH]

tnc110

Saw that boat in ocean city MD. There are several videos of it on youtube. Congrats on the purchase....beautiful ride.
Looks like a solid ride to me. http://www.youtube.com/watch?v=LB7F0JWWXsE
http://www.youtube.com/watch?v=Yu5rdXS_6k8
http://www.youtube.com/watch?v=ehrDAgGiha0

a.altman

That's the one. It is a solid ride. That is with a 5b prop it is. Just looking to workout the blowout issue.