gear box ratios

[fatboy0054]

I am building a 15 ft 500 cad 450 hp . Gear box 2 blade power shift 80 maxius prop . 2.12 or 2.38 Need to decide . good motor all the works .5000 no sweat just need some infor . people say it wont work. But I am , my worst fear . My buddies belive in BB Chevys , cant compete or more money for them . I am thinking 2.38 extra boost . thanks any commets welcome ? :lol: It would give me 2100 at 5000 ?

 

[Anonymous]

With a 2 blade prop on a 500 I don't think you need much reduction. How much pitch will you run?

You also shouldn't need to turn a Cadillac engine 5000 RPM. It is probably making much more torque around 2500 to 3000 than at 5000

Waterthunder seems to be the expert on this, and favors lower ratios, but that's with more prop on smaller motors.

We'll see what he says...

 

[fatboy0054]

Dont know yet , about pitch , My tourqe is alitte above that .550 @ 3200 . What my hp goes on up to 4800 . I dont lose much, only about 30 pounds at 4800 . My hp climbing hard at 4200 to 4800 . 500 is possible at 4800 . Just dont know , My first cad deal trying to save me some time and keep Mr murffey off my back if uno what i mean thanks for the time :lol: That way i could full pitch the prop to get down to the 2,12 @4400. I would have more spin up , or faster turn up with the 2.38 same rpms !I really thankyall for the time ,

 

[Waterthunder]

I’m sure you would be very happy with a 2 to 1 box. Because of their design Caddies produce a lot of torque over a wide RPM range but they fall off drastically after 5,000. I would run a wide three blade Power Shift or Sensenich. I would set the pitch till she max’s out between 4,800RPM to 5,000RPM. At this setting you will cruise the river at a very low RPM if your hull runs free and isn’t too heavy you may plane out as low as 2,200. A lot of people will tell you (YOU DON’T NEED A GEAR BOX ON A CADDY) Well when was the last time you saw a Caddy swinging a three blade wide blade with a lot of pitch in it.

 

[Waterthunder]

P.S. Under no circumstances ever run a two blade Maximums I have tried it and trust me you will not like it!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[fatboy0054]

Thank you sir .very much . MR Thunder . I Really like your View s about gear drive , read every one of them . Like I said . Thank u sir ! Tying to this done with few grimlems as possable . Theres one thing I dont understand . I am building a adjustable rear motor mount so i can tweet , my ride .I dont see them out there . I am new to this kind of boat . Just trying to get the best i can do! Thank you sirs . adjustable prop , mounting too . just wondering . I know people settle for some things. I am building everthing to things i have seen thats ,seems too work .Backyard builder . Keeps me out of trouble . :?

 

[Waterthunder]

Every boat I have ever built has adjustable mounts you got too with a car motor boat. Most the aircraft boat builders have built hundreds of the same exact combination. As in same motor, same hull, same prop so they know exactly where to set things up. Consider this how many Caddy boats have you seen with gear boxes. So how can someone tell you how to set your boat up if they have never built one? You’re on the right track by keeping it adjustable. I can give you one suggestion get the prop as low as you can in your hull consider a 78’’ Power Shift. What you lose from the transom blocking your thrust will be far outweighed by a lower motor that doesn’t push on the noose. When you make big power keeping a boat off the noose is the hardest thing to do.

 

[fatboy0054]

THANK you sir thanks for the time :lol: How far down below trans can i go thanks, I have been to all the boat makers in florida . I have tried to remember the good things, about everthing , I had seen about everthing everbody done . hard to weed out things .will do what you said .Thanks I am on the same page as you !.Like I said thanks :lol: