MacGregorSailors.com

I see Heath has added a new forum and it just so happens I have a topic in mind

I've seen a lot of posts from people claiming to have stock boats/trailers that weigh over 4000#. I'm just curious, is this speculation or have you actually weighed the rig and found it to be that weight

If you have weighed it and found that it significantly exceeds 3500#, could you respond and also list what sorts of options you have on your boat that make it that heavy. TIA

When I found my trailer wagging behind the '97 Expedition at 55 mph, I went to a Mayflower storage yard to weigh the rig. Before doing so, I recommend you insure that the bow is fully forward to its v-block.

3,740 lbs. = Boat & trailer axle on scale, plus nose wheel down on scale.
3,520 lbs. = Boat & trailer axle on scale, tongue resting off-scale on hitch.

This meant my tongue weight was too light at 220 lbs. I moved all tools and spare parts to the forward cabin sole, moved my one fuel tank forward of the pedestal, added a spare to the forward trailer, and sway was completely eliminated at 65mph (California's trailer limit, +10).

These are the weights when my boat was new. Since this includes a Suzuki 60hp motor @ 335 lbs. most new boats should have ~100 lbs. less on the transom than mine. Transom weight is most magnified in trailer balance problems. The aft berth and the fuel lockers are also bad for trailer balance. All internal storage that's forward of the axle position is basically benign to trailer handling. I'm sure my cabin has since acquired some additional weight, probably at just about 4,000 lbs. now.

At a target weight of 4,000#, a tongue weight of 10% would leave a net weight of 3,600 lbs. on the axle. That is slightly over the axle rating, and just slightly less than the rating of the 215x14 tires. The trailer is basically adequate for nearby towing. Since the tires seem to be the weak point, up-sizing them adds some valuable safety margin for longer distance towing (just one opinion). Remember though, balancing the load (8 to 10% on the tongue) is key to safe handling.

I strongly recommend against moving the fenders higher on the trailer by drilling new holes higher on the frame rail. Drilling a hole anywhere on the rail weakens the frame's resistance to bending stresses. Drilling it dead center on the rail (as per the original location) weakens it the least. The farther off center you drill, the more the frame is weakened.

Drilling a new hole directly above the original compounds the problem.

While we're on the subject, never drill any holes in the legs of the frame rail channel for the same reason. You might be tempted to do so to mount wiring or brake line clamps. Don't do it. Even small holes in this location will weaken the frame considerably.

Chip:
Where and what would you do to reinforce the structural framing of the trailer?

Rob H.

If you're talking about reinforcing the area where you want to drill holes off center (or maybe you already drilled) ( ) a 1/4", 4 x 4 steel plate, welded all four sides and centered on the hole, should do the trick.

If your talking overall reinforcement, it's pretty complicated and might not be beneficial. The Mac trailer, is, by design, quite flexible. This has the effect of distributing the loads more evenly over both the trailer and the boat and reducing the peak loading.

Doing the actual numbers would be difficult and fairly time consuming, and ultimately I believe, of little value. My guess is that, in general, the most highly stressed areas are between the front bunk and the rear spring hanger, and the single highest stress point is right where the front spring hanger is welded on. You could reinforce this area by "boxing" the rails along the length, and it certainly will be stronger in that area, but you also will have removed most of the designed in flexibility and the peak loading elsewhere on the trailer might actually be higher. The peak loads on the boat will almost certainly be higher.

Mounting 15" tires will interfere with the factory fender position, since they sit half-an-inch higher from the axle position. One alternative to drilling new holes for the fenders is to lengthen the spring hangers. You can increase the center tire clearance by 3/4" with ~1.5" longer shackles to mount the rear of each leaf spring.

Hello:
I know I'll catch it from Chip on this but here goes. I redrilled my rails to raise the fenders for 15" tires a couple of years ago and have had no deformation of the frame. I have not weighed my trailer / boat so I can not attest to the exact loading. You can't really drill too close to the edge because you won't be able to get the nut back on, so by default, the mod has to be done in moderation. I am not a fan of longer shackles because the trailer is already squirly enough without the added lateral movement and axle steer that promotes sway. The best way, of course, would be to reweld the spindles with less drop but by then you might as well get a whole new axle with 6 lugs and the works unless you are doing it yourself.
Don T.

Why not just cut the the supports that hold the fenders on and then weld another piece of metal in there to raise the fender by an inch? Seems like a job that would take an experienced welder about 15 minutes to do and would not compromise the structural integrity of the trailer.

Good one Dimitri!

Don't lower the river, raise the bridge.

Thank you, Dimitri. Now, one more thing. Because the bolts are located above the centerline of the fender, when you raise the fenders on the brackets (or lower the brackets on the fenders, depending on your point of view) it will increase the spacing between the bolts by a little less than 1/4", and they'll no longer fit in the original holes. Don't bend them to install them or drill the holes oversize. Simply take a file, Dremel, or whatever, and elongate each hole lengthwise by 1/8". They'll fit fine.

Oh, and BTW, you can save a littlle on the welding. Don't cut both brackets off and raise them 1/2" each. Cut one off and raise it 1". The outcome is identical. You might want to do the "forward" bracket on both so you'll have a matched set.

Nelson Thomas wrote:drilling new mounting holes in the frame a bit higher

For those who've drilled the extra hole and are now concerned about strength, you could fill the unused hole by welding it closed, grinding it flat, and then painting it. -Another 15 minute job for an experienced welder.
I went the other route, replacing the spring shackels with longer ones made of heavier gauge steel. Besides seeing no ill effects thus far, I like the extra inch or so in engine height when backing into my (somewhat steep) driveway.