X Dimension 1985 Flat Deck
 

Hi gents. I am pulling the motors next week to freshen everything up. Time to rebuild both short blocks and heads. I think there may a few wet spots in the transom if so I will rebuild that as well if there is in fact water in there. If I do redo the transom I will try and improve on the position of the drives. My question is for the flat deck gurus out there What x dimension works best on these hulls. In other words how far below the hull should one set the prop shaft to make this hull work best. I am not looking for a race set up but something that will give good speed but still able to plane without revving the motors to their death. This hull does not have a notch.
Thanks RG.

What drives are you using Rick? That is an important piece of the puzzle.

Sorry I am mounting No. #3 drives.
RG.

I wouldn't go any higher than having the prop shaft 3 inches below the bottom of the boat. No deeper than 4 inches

Thanks Kvogt. I will measure this weekend when I get out to the shop. I also put a call to Craig Barry who was at Cigarette when these boats were built and he was going to check his notes on where they ran them. He did say it was important not to run the prop shaft too high for fear of not being able to carry the bow. 3 to 4 inches dosen't sound too far off . I am courious to see where they are currenlty set at now.
RG.

I measured a factory cafe, flat bottom no notch an the propshaft was 5" below the running surface. All of the factory setups were very conservative. I will be going 3" on my hawk but it is notched. X dimension of 21.311 will give you 3" below, 20.311 will give you 4"

You guys should both start high as you can always space down but can't ever go up. How long is your notch? Also extension boxes allow you create more leverage at the same given trim angle, therefore allowing for a higher x

I can't really go any higher than that. Cog is going to start giving me problems any higher. Really if you want to be higher than that you need 4's or 5's so your x dimension is 6" lower. I actually don't want the motors as high as they will be but need to have the propshaft there from my research. Boat is too long and heavy to go any higher without boxes or a lot of prop testing to get the bow to carry. I'm moving the engines way up and forward 10". I think any higher will not work out well.

I hear ya but a general rule of thumb is you can raise the drives 1 inch for every 12 inches of a notch or extension box. So if 3 inches below the running surface is the rule of thumb for 3's mounted on a straight transom, then you could go to 2 inches below if your notch is 12 inches. Now if you added 12 inches of boxes you could go up another inch. Just a thought.

Id call this guy and find out where they are on this fountain cause your hull is essentially the same i think.

http://www.offshoreonly.com/classifi...o47611-en.html

Thanks 302 but the 3 drive is the tallest one of the SSM series if I remmeber correctly and going higher than necessary causes other issues such as COG and clearance issues under the hatch. On my 43 Scarab when I had it I put the drives at 2.5 inches below the hull but it had a notch and that worked killer. But even with that setting my N/A engines were almost touching the hatch . I would like to get it as close to perfect as I can can without spacers .

RG.

Rick can you email me some info on your scarab setup? Power props etc? That's a similar hull to mine curious how it planed, handled etc.
[email protected]

Al has the boat now. I gave him my temp plate dimenions as he said he was going to help you sort your hull. When I set the drives on the Scarab I talked to Dan M at Team Archer Marine in CA they are the scarab gurus and work with with Larry smith on set up. With my 725hp N/A mills and 4 blade 25 pitch props I would walk it on plane quickly and not break 3,000 RPM . I had the prop shaft set at 2.5 to 2.75 inches below the hull and it worked perfectly. Al tells me with his 1,100 hp mills and I think a 32 pitch prop he can almost get it on plane with one motor.
RG.

oh ok now i know the boat! didnt realize you were the same guy! cool thanks for the info. was worried about how mine was gonna plane, didnt want to be dropping tabs all the way and holding at 4,000 to roll up on plane. then play the balance game. sounds like it worked well and in a way i'll be happy with.