Trailer Leafsprings Bottoming Out

[boltentoke]

Hey guys. I recently bought an older boat with a homemade trailer. Someone towed it home for me and it has been parked since, so I'm not familiar with how the ride/suspension was.
I just replaced the leafsprings. I have no idea what rating the old springs were, they were basically rusted to dust.
The boat (560lb) motor (205lb) and gear (currently nothing in the boat, let's just say 200lb) weighs around 1,000lb. I bought 4 leaf springs rated for 1,750lb. They are attached to the leafspring hanger bracket using 4inch shackles. But when jumping on the trailer (unloaded) the shackles bottomed out and got stuck. The left side seemed to work just fine though (see video). After tightening the bolts a bit it seemed better, so I put the boat back on the trailer, and when I lowered the full weight of the boat onto the trailer the shackles instantly bottomed out, as seen at the end of the video. After jacking the trailer up till the wheels were off the ground, they popped back down to the original position.
Can anyone help figure out what is wrong? Do I need different length shackles? The springs are the same size as the previous ones, just with an additional leaf.

https://imgur.com/a/lk9f6yp

 

[kenny nunez]

The spring eyes are too far apart for the anchor points. Just have a welder cut the rear shackle mounts and move them back to where the shackles are vertical.

 

[Lou C]

Your springs are too long. They come in all different lengths. Measure the distance between the mount flanges where the center hole is, that's how long the springs should be when measured eye to eye. When leaf springs are loaded they get longer. With the trailer unloaded your spring shackles should be close to vertical, those are way out of wack!
try calling Eastern Marine in Delaware or Champion Trailers in Louisiana and give them your spring mount measurement, they can tell you what size springs you need.

 

[Scott Danforth]

You bought the wrong length springs

 

[Chris1956]

First of all, put the leaf springs on top of the axles. The way you have them means the ubolts must take all the pressure from the boat's weight. They were never intended to do that. BTW - the plate should face up.

The springs are a bit long. Is there any way to spread the anchor points for the springs apart?

 

[Lou C]

Actually most boat trailers I see that have spring axles have the springs under the axle like that. It’s done to lower tide height and is common on leaf spring cars if you look at old Mopars with torsion bars up front & leafs put back. Nothing wrong with spring under set ups your problem is the springs are way too long!

 

[Chris1956]

Lou, You are asking a lot of those 3/8" u bolts to hold the entire weight of the boat, when you hit a pothole at 70MPH. You are also reducing the travel of the springs, by the thickness of the leaves, and there was not a lot of travel to begin with, so the boats sits lower on the trailer?

Boats already have a low center of Gravity (COG). Spread the rollers further apart or adjust the bunks to lower the boats COG.

At least that is what I would do.

 

[Lou C]

My Load Rite & every other LR and Venture trailer I have ever seen is the same. When I changed the first axle years ago I had the same though as what you’re saying yet that is pretty much how it’s done.
PS ever hear of a failure? My single axle has a 6000 lb axle on it and the load on it is 4650 lbs.

 

[Chris1956]

Also, a lot of leaf springs have center bolts or rivet heads that fit into the pocket on top of the axle. These positively locate the position of the axle, to keep it from sliding back on the leaf spring.

He could change over to 1/2" ubolts to increase the strength. That would help, however, I am not a structural engineer able to calculate the breaking strength of the bolts, vs the shock of hitting something at 70MPH, with a 3000# load on the trailer.

Gee trailers fail all the time. How many shackles/axles/springs break pulling the boat out of the water at low tide? At low water the wheels go off the end of the ramp, and when you drag it out, stuff often breaks.

 

[ahicks]

Agree springs are too long, and that axles should normally be located on top of the springs. Anything is possible, but I have never seen or heard of a U bolt failure.

Further, if your weight alone is collapsing the spring as shown in the video, they are WAY too light, no matter what they are "rated" for!

 

[Lou C]

20 years same trailer with a heavy 20’ boat on a single. No failures!

 

[boltentoke]

Thanks for the replies.
So I went to the local boat trailer repair/manufacturing shop and showed the guys the same video. They initially suggested the same, that the springs are too long and I should go down a size, from 25 inch down to 23 inch and make sure I measure the the distance between the two eyeholes of the spring hanger bracket. So I bought them, went home, and installed. They definitely do not fit. The spring hanger bracket is 25 inch from eye to eye. The 23 inch springs were too short, the axle is now farther forward and hitting the keel roller & crossmember. Even if I slid the hanger bracket back farther, the spring was 2 inches shorter than the bracket anyways, so the shackles now had a steep inward angle (bottom eye of shackle closer to front of trailer) which is the wrong direction. So I called the shop back and explained this. The guy on the phone said it sounds like I just need longer shackles on the 25 inch springs. So I went out and grabbed the 5 inch shackles to replace the 4 inch, and installed with the 25 inch springs. The angle of the shackles is much better and now the boat sits fine on the trailer even when bouncing inside the boat hard as I could. Have yet to road test, but looks much better and should be good to go.
As far as the springs being above or below the axle, I have seen and read about both. They are two different designs, depending on the needs/application. For this trailer they were designed to be below the axle as you can see in the video. As Lou C said, It would make sense since I live on the Florida coast, where there are very few bumps or curbs, and boat ramps are highly susceptible to tides so the lower ride height can be key when coming/going in low tide.