Need Help Setting up a Deep V

[MalibuSkier]

I have been running a 32" deep V w/ a 7.5 K&B outboard. The CG was at about 15-20%. The boat ran fast but VERY loose. It would dance side to side and beome unstable after 10 yds. When the prop would bite the boat would jump right out of the water. So after some reading I added about 2.5 lbs up front (along the keel) to get a CG at 33%. The boat seems to take off well, but it runs on its right side. Giving it throttle makes it roll even farther and just about upside down. Right hand turns just about rolls it over. Left hand turns are flat. I have the top of the prop shaft just about even with the bottom of the boat. I assume I have a very bad torque problem. Why now with all of the weight? Does the prop need to be lower? higher?
Suggestions would be very much appreciated.

[BoatDoc]

i have a 3.5 cc outboard that acted a lot like that. what you need to do is add trim tabs and a turn fin. make the tabs as big as you can while still allowing the motor to turn all the way. you really only need a turn fin on the right side. the reason you get so much roll is the torque of the motor combined with the turning of the outboard unit itself. my 3.5cc boat is 31" long...so you've got a lot of power pushing that boat, which means you will probably always run a bit "loose" but the tabs and a turn fin will help calm it down. that side to side dancing (chine-walk) can be a little nerve racking, but at full speed you'll still get a little of it. get used to it!!! if you have an adjustable engine mount(i believe they are a necesity)...you can play with the prop depth and angle...but too much will make the boat act funny. i prefer to use engine height/angle to get into the ball park and the trim tabs for fine tuning. hope that helps.

[BoatDoc]

if you want a better idea of what i'm talking about with the trim tabs...check the thread in racing nitro/gas titled "prather vee has new paint" that's my boat and you'll see the way the tabs are cut so that the engine will clear them.

[MalibuSkier]

Boatdoc, I do have trim tabs installed. I turned down the right side to a very steep angle but it didn't seem to help.

Any idea why I see the hard roll to the right now that I have weighted the front end? The boat ran pretty even (no roll to the right side) when it was light, it just seemed way to loose (and the back end would swamp because it sat at a pretty awful angle when still in the water).

I'm thinking about taking some of the weight out. What I don't like is how steep the boat sits when it's still in the water. The water just about comes over the transom and will swamp now and then. It also starts to move the CG back to a position I think is a little to far.

[MalibuSkier]

Boatdoc, I do have the adjustable mount. The engine is trimmed out a little now to raise the front end slightly. I get just a little rooster tail so I think it's about right. What happens if the prop is way to deep? or way to shallow?

Thanks

[BoatDoc]

i just had to make sure about the tabs and turn fin. the leaning is most likely being caused by the torque of the prop. like i said, that's a lot of motor for that 32" hull, so that may be part of it. prop angles can play heavy on this too. when i trimmed mine out, i set the prop 1/8" below the keel at a flat angle for a base line. the only adjustment i made was to angle the prop to raise the bow a bit. the weight in the front is causing a little of the lean too. it has more to do with shifting the c/g to the right or left as the boat turns. if the weight is low in the boat, you should be alright. if it's too high, the boat will role a lot. about all i can say is maybe you should go down one size on the prop and just try to spin it faster. that will take away some of the torque roll. btw...what type of hull is it??

[MalibuSkier]

Boatdoc, thanks for the input. I think I have the prop height and angle about where you suggest. The weight I added was layed down in the keel and shaped to fit the V to make sure it was as low as possible. I'll try a smaller prop to see if it helps. If not, I'm planning to start removing weight and see what happens. I just thoguht that by adding the weight it would stabilized things. I don't get the chine walk but running down the lake on its side is pretty harry.
The hull is about 20 years old and I think it is a Prather (fiberglass). I've been out of the hobby too long and don't remember exactly how I had it set up years ago. I remember alot of chine walking but never the hard roll on the side. I know all the xtra weight is a new addition.

Thanks,

[BoatDoc]

mine is a prather, and about the same age! i was out of the hobby for a few years myself. i remember running this boat with no tabs back when i first got it. but after refitting it with some new gear, the tabs had to go on because the boat was out of control.

[Chilly]

Sorry to budge in on you here, but just a quick thought...have you finished your prop? Cause to me, this sounds a lot like if the prop was dragging your boat, or propwalk. Either that, or your engine is mounted to high in the enginecompartment, and thus tilting the boat at high revs. Just my thoughts, it might very well be wrong...

[Ron Olson]

Take some weight off the front so that the CG is closer to 27%. Outboards on monos are funny animals, weirder yet because OB's are common on full-sized boats. Yes, you are overpowering the hull as that size does better with a 3.5 hung off the back.
When putting on the trim tabs, mount them 1/16" above the bottom of the hull.
Work on the motor height for the chinewalking problem.

[Watercadet]

I'm with chilly. That prop had better be sharp and balanced or you will get that kind of torq.
Adam

[Chilly]

I´m no expert whatsoever, hav not been running boats for more than one season yet, and no competition or anything. Just built a hull by myself, for the fun of it. However, I have done a lot of research, and to me, this sounds like an improperly finished prop.