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PROP HEIGHT???

R

ROBERT JAMES

Well-known member
MY COUSIN AND I WERE TALKIN 2NITE AND GOT ON THE SUBJECT OF HOW HIGH OR LOW YOUR PROP SHOULD SIT IN THE BOAT. HE SAID IN HIS OPINION THE LOWER HE COULD GET IT IN THE BOAT THE BETTER HE LIKED IT AND WHEN HE ASKED ME WHAT I THOUGHT I WASNT SURE?? SO IS IT BETTER 4 THE PROP TO SET LOW IN THE BOAT OR WHAT IS THE BEST HEIGHT
 
I'm sure everyone who builds boats has their opinion. Mine is, I set the prop 5 inches down inside the transom (from the top).
 
Depends on the hull and prop. You will make more thrust with 100% of the prop out of the transome but this will also make most boats run worse!
 
The higher the motor the harder it is to keep them from riding on the nose and the more the boat will torque roll. Sometimes loosing a 100lbs of thrust will drastically improve how a boat rides! You will not feel this so much on boats over 2,300lbs or over 16ft long but you build a light medium size airboat and those 6 inches of height will COMPLETELY change how loose and how well the boat rides!
 
Does this effect interact more with geared boats as opposed to sbc direct drives like mine? I never thought about that but , damn! It sure makes alot of sense.

thanks
andy
 
So you guys are saying that the thrust you lose by that couple of inches of prop will be made up for in the lower engine height? How much do you really lose on the very tip like that? I haven't heard much about this, so keep the info coming - it helps out a lot. This forum is awesome. I just barely found it and have learned a ton of stuff from you guys.
 
Waterthunder said:
The higher the motor the harder it is to keep them from riding on the nose and the more the boat will torque roll. Sometimes loosing a 100lbs of thrust will drastically improve how a boat rides! You will not feel this so much on boats over 2,300lbs or over 16ft long but you build a light medium size airboat and those 6 inches of height will COMPLETELY change how loose and how well the boat rides!
Click to expand...

Just like taking a glass of water 3/4 full push it from the top it wants to tip push it from the bottom or below the half way point slides just fine
 
waterthunder i thought the angle or degree of motor keeps it from riding on bow,
like trim on outboard makes bow up or down...angle of prop..

moving gas tank beer cooler etc.toward rear or forward for porpiosing?? fine tuning

cont520 i understand glass of water principle but is that not for the way the boat floats not how its proppeled forward....

i'm tring to understand what the same thing this guy is asking for rigging my boat
 
Its for both ,but mainly how a boat pushes depending on hull length .For shorter hull runners like 10'-13-6. The lower the better that dont put you prop to far in the hull I dont like to run any prop in the hull but I also sacrifice length I run a 72'' prop only have a 1/2"in the hull now. when I get my new one there will be less. You can adjust the motor angle and what not that will help you a little but if you build a sky scraper engine stand its not gonna matter it will still try to push over the front .Just for the fact of the rear trying to push over the front
 
now i understand what your saying, thanks you guys do really help out, i know your wisdom did'nt come easy or from a handbook................................
 
http://www.southernairboat.com/photopost/showphoto.php/photo/14150/ppuser/1734/sl/c This is the best pic I have thats a 74" prop that I built it for but I run a 72" when I race. As you can tell the prop isnt far into the hull Also I have 16"sides on this boat
 
How does that wisdom change when you are dealing with small 10-11 ft deckovers? I have seen quite a few with 68" props but few with 72" and over. Wouldnt bigger be better to certain extent anyway?


Tony
 
I dont know anything about Deck overs just that everything is out of the hull any ways so you dont have to build as tall just enough to suit what prop you might run
 
I think you will get different answers for different styles of boats. I'm sure you would not set up a race boat the same as a ride boat. when I bought my prop for my caddy boat, I was told by Sensenich and Hamant that up to 6'' of prop in the boat is OK for a ride boat. It important to keep the center of gravity as low as you can. I am sure that it makes a lot more of a difference with my big Caddy than it does with an A/C motor. But the lower the center of gravity the better the ride will be.
 
Hey can i get in on this.Maybe you can answer one for me.I was told that if iI lower
my transome and ade in a splash plate that i would have more push.This way I would
use the full prop.
 
Waterthunder said:
The higher the motor the harder it is to keep them from riding on the nose and the more the boat will torque roll. Sometimes loosing a 100lbs of thrust will drastically improve how a boat rides! You will not feel this so much on boats over 2,300lbs or over 16ft long but you build a light medium size airboat and those 6 inches of height will COMPLETELY change how loose and how well the boat rides!
Click to expand...

I also wanted to add that if you have the prop down to far in the transom that will also cause the boat to push on it's nose.
 
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