Drive Too Low or OK?
 

I've been trying to dial in my boat all season. It's a '08 Velocity 390SS with staggered stock 525's and stock XR drives. I've been fighting extremely high prop slip(20+%) with numerous props, so I decided to drop the drives 2". This put the center of the shafts even with the bottom center of the boat. What I didn't consider is that the cavitation plate would end up about 1/2" below the notched transom. The results were interesting, though. I ran exactly the same top speed as before the spacer, but with 400 less RPM, lowering prop slip by 8%. Cruising speed and RPM also are identical. Planing is greatly improved and the boat feels rock solid at WOT. I shot a video today to see if the drives were too low. It's not the greatest video, but I do see a bit of water getting over the plate. Is this cause for concern or no big deal?

http://vidmg.photobucket.com/albums/v215/dpluhm/New%20Velocity%20Paint/2spacer_zpsejtzwark.mp4 [ATTACH=CONFIG]545438[/ATTACH]

Interesting

Give us more information please

Do you run diffuser rings

Would be interesting to try a 1" spacer also :D:D

Thanks for sharing!

Kevin, here's what I've run this season. None of the props had cut down rings.

Hering 6-blade - 21.5% slip, fastest
Mercury Maximus - 19% slip, -4 MPH
Hydromotive P5X - 23% slip, barely got on plane, -6 MPH
Hydromotive P5 w/longer welded ring - 20% slip, tough to plane, -1 MPH

BTW, I can't believe you don't have a strong opinion about the height. Now that you're married, do you have to ask the boss first? :)

Dropping 2" is a ton. I would try 1" spacers.

Its obvious that dropping the PS centerline is giving the props cleaner water reducing the slip. This also will help provide more leverage to carry the bow. Appears a step in the right direction. Dial the props back in pitch wise to put you at max power and you should net speed increase.

i don't suppose you have the same video without the spacers? that might be interesting comparison.

[ATTACH=CONFIG]545544[/ATTACH][ATTACH=CONFIG]545545[/ATTACH]86 scarab panther
I have been dealing with the same drive height issue. first trial no spacer on able to get on plane at all. I put a 1 inch spacer and was able to get on plane and ran 87MPH one time the day was mid90's and humid
this past weekend I put a 2 inch spacer on and ran 87mph every pass and the boat obviously got on plane better
temp. was probably 80 degrees and not quite sure of the fuel level difference
the one thing I do not like is the bravo upper gears housing are out of the water when at idle so after running they are not getting cooled by bay water.
so I am at minimum pulling the engines and lowering 2 inches but I am debating on 3 inches

Put some better lowers on , imcos or sportmasters , water being blown away from props ? and go back up .

Why not just ditch the boxes? or go with neatrals? Seem like a ton of work to try to cool the drives. I dont see drive showers either, if they are properly cooled at speed, why would they need to be in the water at idle?

Just throwing it out there

I think if you put a spacer to match in the port side drive you`ll get even better results!