See full version: How To Set Up a Boat Trailer
If your current trailer does not qualify as a good candidate, (Be honest wth yourself) then you'll honestly be better off playing some Pacman while you think about how you're going to get yourself a trailer that is going to make a good candidate.
First you'll need to determine if your trailer is a good candidate to work with. The style of boat trailer on the left, will not work well for anything more than like a 13' aluminum jon boat. The style of trailer on the right, is what you're going to want to start out with. Your keel should be able rest inside the frame rails, with at least three crossmembers that are perpendicular or "not parallel" with the boats keel.
Here is an overview of the parts that will need to be adjusted, or installed. Then we'll make our four critical adjustments.
Instructions for fitting a boat to a new Venture Aluminum Bunk Trailer:
1. Make sure your tow vehicle has the right ball size [2" for singles and small tandems. 2 5/16" for tandems over 6,000 # boat load capacity and all triple axle trailers. With capacity equal or greater than the weight of your boat with all tanks full and gear and the weight of the trailer.
2. Make sure you have the right electrical connector and that all leads have power when the appropriate light or action is set on. Ideally you have a flat 5 connector if the trailer has standard surge-disk brakes or a round 1.5" dia. RV type 7 pin AND a 7 : 5 adapter you could buy at Wal-Mart or most auto parts stores. If you ordered your trailer with the optional EOH electric brake controller to operate the hydraulic disk brakes, you need a round 1.5" dia. RV type 7 pin connector on the tow vehicle.
If you have surge brakes and only a flat 4 connector, you will be fine for most towing situations. If you have to back up either uphill or where there are speed bumps or large potholes, you will need to plug the end [5th] pole of the trailer wiring harness into the 2nd pole [1st female connector next to the ground connector] and put your parking lights on. This will energized the 5th pole with 12 volts which will operate the solenoid on the back of the surge brake master cylinder, effectively disabling your trailer brakes. Drum brakes on a boat trailer usually do not work and if they do, doesn’t work effectively in reverse, hence no need for this solenoid and wiring. Disk brakes work just as efficiently in reverse as forward.
3. Measure your boat from the bow eye to the transom. This is the bow eye length.
4. Transom of your boat should hang off the end of the bunks 1-12 inches. Make sure bow stop is far enough forward to allow this and move it one foot further forward than that for the first loading.
5. Make sure the target bunks are set to the lowest by loosening the set screws so they are mostly out of the way for the first time pick up.
6. The main bunks will likely not have to be moved, unless they are set where they would rest on something like a water pickup or hull transducer, or right at the point of a longitudinal stringer or angle on the boat bottom. If so move them in towards the center of the trailer the minimum movement necessary to clear. It is important to get the bunks set as wide as possible for lateral stability.
7. Lower your trailer on the hopefully steepest ramp you can easily use so the the target bunks are just barely sticking out of the water. This position is several feet further up the ramp than when you launch and float your boat off the trailer.
8. Put the boat on the trailer in contact with the target bunks. Release out enough winch line to hook it up. Put the winch in low gear by moving the turning handle axle so the little gear on it makes contact with the gear nearest the handle, to make it easy to turn the winch handle.
9. Do not winch it all the way up to the bow eye as you left about a foot to spare. You can reduce or eliminate repeating steps 9-11 by:
a. if your boat is already on its old trailer and the tongue weight/balance is good, put tape on the boat over the center of the center axle on triple axle trailers or right between the axles if tandem.
b. if 9a is not possible, google search “boat make model” and ‘trailer’ then click on ‘images’ to just see pictures of your boat model on a trailer. Note on the picture that part of the boat that is over the center of axles above, like a letter of the boat name or the edge of a window or or some part. Use this point to load your boat on the new trailer centered on the axle set center.
10. Pull the boat far enough out of the water to measure where the transom is compared to the back of the bunk. For rear engine power boats only: Repeat steps 7-10 to get the transom hang over to 1-12 inches. Steps 9a or 9b are more accurate loading plans.
11. Move the boat up to flat ground. Check the approximate tongue weight by blocking tires on trailer and completely unhooking trailer ball connector. Turn the tongue jack and feel the pressure. It should be hard to turn but not awfully hard. Better to have too much tongue weight than not enough. You may have to repeat steps 7-10 to get the tongue weight about right.
Correct Tongue weight is way more important than overhang at the back of the bunks. If too light your trailer will sway side to side at high speed. It is ever does this; gently release power to slow down very gently.
12. Move the bow stop and winch stand back and up or down so the yellow bow roller is touching the boat with the bow eye just behind and below the bow roller.
13. Attach transom straps. Tighten winch and attach safety chain to bow eye.
14. Drive slowly [under 55 or 50] home
15. The tongue weight should be about 7% of the total loaded weight of boat and trailer and fuel and gear, so about 500# for a tandem and about 900# for a triple. You can accurately weigh the tongue weight by using a 4 ft. 4x4, pile of blocks and a bathroom scale. Set a pile of blocks to 4 inches below tongue height, and 12 inches center to center to one side of tongue. Put the scale with blocks on top of it 3 feet opposite the other pile of blocks. This leverage will mean your bathroom scale will read 1/4 of the tongue weight, so if the bath scale says 200, the tongue weight is 800. See trailering PowerPoint download on my web site to see a diagram of this.
16. Adjust target bunks up snug to the hull. The target bunks carry very little load while trailering. Their primary purpose is when putting your boat back on the trailer; they guide the bow towards the bow stop. Their secondary purpose is reducing fore-aft rocking of the boat while on the road, as the aluminum I-beams flex more than the steel counterpart. This flex is not only not bad; it is good to cushion the blows of road bumps to your boat.
17. Re-Tighten all bolts you have adjusted and wheel lug nuts after ten miles of towing.
18. Have fun boating. Remember the tip when picking up your boat to have the trailer further up the ramp than you do when you launch. Winching your boat several feet to the bow eye will results in a better centered boat and less load on the tow strap when you pull out and the boat will be right up to the bow eye. If you put the trailer all the way out and put the boat on it, when you pull out there will be a gap between the bow eye and the bow roller which is UNSAFE for two reasons-- the tongue weight will be too low making the boat and trailer sway at speed. If you have a panic stop or have an accident hitting something in front of you, the boat will slide forward and may cause damage due to the momentum it has built up moving before it hits the bow stop. The bow stop is designed to keep the boat stopped in its position only if the boat is not moving on the trailer when it hits the stop.
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Step 10. If required in your state, register your trailer and install the tag on it. Double check tongue weight, clearances and bunk and vee block adjustments. Not sure? Call us at 888 278-1991 or email your concerns and pictures to info@topnotchmarine.com. here
THINGS THAT REQUIRE EXTRA ATTENTION WHEN BUYING or ADJUSTING A BOAT TRAILER. [links]
Step 3. Prepare the new trailer by loosening the winch stop "Picture 1" and moving it as far to the front as possible. Remember to leave room for your vehicle to clear the trailer when turning. Be sure to tighten the nuts once the winch stop is moved forward because you will need to use the winch to get the boat positioned properly on the trailer.
Step 4. If the trailer has side guides installed remove them. Stretch the winch strap or cable to the back of the trailer and rest it on the frame of the trailer. You will need it in step 6.
Step 2. Using a local boat ramp launch your boat in the water and off your old trailer.