If you move the boat forward on the trailer, the tongue weight will increase not decrease. .. However your 27 pounds is about the same increase I got over the current 70 pounds the OP said (actually said 60 to 80).
What I did.. First estimate the current distance of the boat mass in front of the pivot (trailer tires)
70 pounds * 12 ft = 2000 pounds *D
D = 0.42 ft. Ie, the boat mass (neglecting a few things) is centered.42 ft in front of the axle
If the boat center of mass is moved forward by 2 inches, the new D is .586 ft in front of the axle.
Tongue wieght * 12 ft = 2000 pnds * .586 ft
New Tonque wieght = 97.6 pnds
At least I think LOL.. And Im not sure why the OP said he could move the boat forward by 2 inches. I know with the Macs (which you and I have), they often get loaded with the boat sitting back a couple inches or more from the front stop and it can make the boat tow unstable.
What I did.. First estimate the current distance of the boat mass in front of the pivot (trailer tires)
70 pounds * 12 ft = 2000 pounds *D
D = 0.42 ft. Ie, the boat mass (neglecting a few things) is centered.42 ft in front of the axle
If the boat center of mass is moved forward by 2 inches, the new D is .586 ft in front of the axle.
Tongue wieght * 12 ft = 2000 pnds * .586 ft
New Tonque wieght = 97.6 pnds
At least I think LOL.. And Im not sure why the OP said he could move the boat forward by 2 inches. I know with the Macs (which you and I have), they often get loaded with the boat sitting back a couple inches or more from the front stop and it can make the boat tow unstable.
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