There are two reasons why you would want to adjust the axles on your boat trailer.

1) The axles/ suspension is out of alignment.

2) To achieve the optimal boat trailer tongue weight of 5% minimum to 7% maximum when the trailer is parallel to the ground.  Sliding axles forward or moving your boat back will lessen tongue weight. Sliding axles back or moving your boat forward will increase tongue weight.   

Venture trailers recommends min 5% to max 7% tongue weight however when researching on the web on the subject 10% to 15% is recommended. Why the discrepancy?  The recommended tongue weight of 10% to 15% is intended for R.V. or cargo type trailers which have very short to no tongues creating much less leverage against them. In contrast,  boat trailers require very long tongues, sometimes up to 10’ extended beyond the main trailer frames, in order to accommodate the length of a boat. There is much more leverage created due to the design of boat trailers therefore they require the tongue weights to be at 5%-7%.

All Venture Trailer models with the exception of some Jon boat and PWC models have adjustable axles. Axles can be slid forward or backward by loosening the frame mounting ubolts and sliding the axles/suspension equally in either direction. It is important to first measure from the end of the frame along the bottom of the frame to each spring mount or edge of the torsion axle mounting bracket, depending on the type of axle you have. Measure BOTH sides of the trailer frame to make sure the axles are mounted at the same location on each frame rail.