Trim Angle between 31's

[moguls2go]

Educate me. Why do certain 31's appear to run with a very proud bow (pic #1, yours truly), while others run at a very flat angle (pic #2, pulled off the net)? I noticed that Priceless (thread: Priceless has a new look) looked more like #2, as does Phoenix and others. Why is that?

[Priceless]

Can't include Priceless in that. All those pictures were "Glamour Shots" taken in the Indian River Inlet at less than full planing speed for effect. Will get photos at cruising speed from an adjacent boat in the ocean some day.

[Charlie J]

the last pick is of current affair rounding Montauk
before she was painted
I believe cap pat took that pic

[Navatech]

the last pick is of current affair rounding Montauk

What's that color scheme?!... Green antifouling for the bottom and boot stripe, fighting lady yellow for the hull and white topside?!...

[Charlie J]

black bottom paint, and boot stripe then
now ice blue or palm beach blue w/ black boot stripe.

mogos
I was probably turning at least 3000 rpm in that pic
that's why the bow is down

[Carl]

Boat squats till she comes out of the water. Rides bow high.

As boat goes faster hull rises out of the water onto her strakes, nose comes down, less overall wetted surface =faster and more efficient.

Continue even faster, the angle of shafts pushing up into the aft hull portion drives stern up, bow down, boat gets squirrely as bow steers. That is when changing shaft angle to something lesser comes into play. Old boats like mine have 10 deg angle, but can't swing big efficient wheels with short strut. Bob brought his motor down to hull to flatten shaft angle...others like Carl from Elite extend shaft back further to lessen angle and some use prop pockets for same effect.

So in short...the reason is speed

[1962 31]

heres mine at 22 knots I lowered my engines way down and back as bob did and took 2 degrees out of my shaft angle
but with 210 cummins I don't go very fast but im more bow proud than with the gas motors and very efficient

[bob lico]

that looks great for cummins 210`s . nice bow proud trim angle for offshore running.lowered engines also produce lower center of gravity (less pitch and yawl). great job!

[Pete Fallon]

Moguls2go,
Speed, speed, speed, the faster the boat goes the flatter the running angle, at high speeds the boat is running on the lifting strakes, like Carl said. Also some of the 31's had lower profile struts 9" to the center of the strut barrel and the bottom of the hull, they had intermediate strut bearings just aft of the shaft log exits, and the shafts were longer to make up for the flatter angle. My 31 express came with 106" long 1-1/4" shafts and intermediate struts, the boat had direct drive trannies that turned small props 16x11 3 blade. I could only do 30 miles per hour at WOT with the old 440 Chryslers and it burned fuel like crazy over 60 GPH at 30MPH. When I replaced the 440's I went with 8 degree down angle Hurth 1"5"1 trannies , kept the same shaft set up and changed props to 17x19 3 blade, I increased WOT to 41.8 on GPS and could not get the throttle bodied fuel injected Mercury 310 HP 454's to burn more than 22 gallons per engine and my cruise went from 18 MPH@ 3000 RPMs to 30 MPH @ 3000RPMs . I had 0 back pressure with 5" exhaust system out the transom and the boat was dialed in after a lot of tweaking of the props and shaft angle. I only had 1-1/2" between the tip of the prop blades to the hull boat, any less than that you will get cavitation burns in the fiberglass hull bottom.
So the flatter the boat runs the faster she goes, 31's like to run fast and at speeds over 40 MPH it will start to walk on it's chines and becomes very squirrelly to steer.
Pete Fallon