single/tandem trailer 18' boat

[salmonee]

I've been wondering why the same boat is on single trailer at times and tandem at other. Why is that? If the single is good enough, why do some dealers put the boat on a tandem trailer? I just came home from looking at a sea pro 186 dc. The boat was on tandem trailer. Looking at the spec, it weighs 2085lb dry and without motor. Some Stripers I'm looking at weighs ~2400lb dry w/ out motor. One in particular that I'm going to look at is on single trailer. The 115 yami probably weighs 500. However, i see the same striper on a tandem trailer also. I'm sure the tandem is better for weight distribution. Wondering what the limit is for boat on single trailer?

 

[Silvertip]

Re: single/tandem trailer 18' boat

Single axle trailers are limited by the capacity of the tires and axles. A single axle trailer typically has a 2200 or 3500# capacity axle. So lets look at numbers. The trailer itself is part of the weight the axle must support so a 500 - 600# is in the trailer. Add a 2000# boat and you have 2600. Add a 500# motor and you have 3100#. Add 30 gallons of fuel and you add another 180 pounds. Add a cooler, skies, fishing tackle live jackets. and other assorted stuff. Get the picture? With this set of numbers a single axle trailer is approaching its axle weight limit. Now you figure out which dealer is doing his customer a favor. The one that is charging him a little less for a single axle trailer or the one that convinced his customer a tandem is better. It is all about "total" weight -- not just the weight of the boat. That tandem trailer has two 3500# axles and would have a 7000 gross vehicle weight rating (GVWR) provided it was equipped with tires capable of carrying that weight. With the single axle trailer, there are certainly tires that carry the load but that's a moot point since the axle would be over loaded.

 

[cbavier]

Re: single/tandem trailer 18' boat

It probably depends on how heavy the trailer frame and wheels and tires size.

Mine is a single axle 3900 Lbs Boat on 3x4 in trailer frame with heavy Springs and 15 in tires. Tandem would have been better I think but that's what I got. They said my trailer could haul up to a 21 ft boat. 5,500 Lb capacity on the plate. I had my boat and trailer weighed fully loaded and tank full of gas to be sure of the weight and sure enough, it weighed 3900 Lbs on the scales.

 

[salmonee]

Re: single/tandem trailer 18' boat

silvertip,

The numbers you gave out seem awfully scary. I looked into the new striper spec and it shows 3500#. The design looks the same as the '02 I was looking at. The number being so close to the limit. Looks like a boat dealer would have a lawsuit if the trailer should fail.

 

[reelfishin]

Re: single/tandem trailer 18' boat

Towing wise and maintenance wise, I prefer a single axle over a tandem.
A single axle trailer is easier to maneuver, won't eat up the grass or mark up your pavement when turning and are far easier on tires.
A single axle makes for one less set of brakes to maintain, on less set of bearings and tires to buy when the time comes. I've gotten rid of all of my tandem axle trailers, even the lighter ones.
If you drive on any toll roads or bridges, they will also cost you more in toll.

You can buy a pretty stout single axle trailer, when in doubt go heavier. For the most part, unless your boat is over say 5,000 pounds, I'd go single axle.
I would also think you would also save gas towing a single axle versus a tandem as well.

 

[cbavier]

Re: single/tandem trailer 18' boat

silvertip,

The numbers you gave out seem awfully scary. I looked into the new striper spec and it shows 3500#. The design looks the same as the '02 I was looking at. The number being so close to the limit. Looks like a boat dealer would have a lawsuit if the trailer should fail.

Well salmonee the Boat and Trailer are 1986 and haven't failed yet. The winch did fail and has been replaced. I really can't imagine a 21 ft boat on it but Four Winns surely knows what they are selling. The boat and Trailer are always kept inside storage for the winter and that I'm sure has helped to preserve the trailer since I have only had to refinish it once. That was four years ago. It's still in storage. It's also had three (I think) sets of tires on it. Plus two new Fenders from backing into Docks. I've remedied that problem now too. I'll be looking them (Tires, Brakes, Trailer Frame) over real good this Spring too. Bearing buddies have also helped maintain the Spindles and Bearings. I do plan to replace the safety chains this Spring. I already have the chain.

 

[redone4x4]

Re: single/tandem trailer 18' boat

mines a single axle with a 18' bayliner Capri. weighs 3360 lbs including the trailer. all the boats we had growing up that size were on dual axles. i figure bayliner was cutting costs and went with the single. it is ALOT easier to move around by myself. i push it in and out of a warehouse all the time. I like the added security of tandem axles though. but, even if you blow a tire on a tandem, you still cant keep driving on the other 3 tires like some people think. so im not so sure what the advantage would be on such a small boat.

 

[woosterken]

Re: single/tandem trailer 18' boat

here is my '74 MFG (17'3" loa) on the trailer.the trailer has same mfg. date as boat!
over kill PROBABLY but looks cool !!!
thats my #1 son

woosterken

 

[salmonee]

Re: single/tandem trailer 18' boat

I went to look at the manufacturer trailer "king". The trailer has rollers and listed a load capacity between 2100 and 2500lb depending on trailer size. I'm sure it's over design but it seem like the trailer should not be able to hold this striper I'm looking at. I'm sure dry the boat/engine weighs close to 3k. Alone that should disqualify the boat from being on a single axle trailer.

So If I understand correctly, the trailer should have a weight capacity on it somewhere? I'll have to look at the plate when I look at the boat.

 

[cbavier]

Re: single/tandem trailer 18' boat

I went to look at the manufacturer trailer "king". The trailer has rollers and listed a load capacity between 2100 and 2500lb depending on trailer size. I'm sure it's over design but it seem like the trailer should not be able to hold this striper I'm looking at. I'm sure dry the boat/engine weighs close to 3k. Alone that should disqualify the boat from being on a single axle trailer.

So If I understand correctly, the trailer should have a weight capacity on it somewhere? I'll have to look at the plate when I look at the boat.

Don't forget to add weight for all your gear. Probably 2- 300 Lbs. That might be kinda high but better safe than sorry. My trailer is titled at 875 Lbs if that helps you any. I think Fourwinns lists my Boat at 2900 Lbs engine and full tank of fuel. 27 gallons @8.4 Lbs per gal. You do the math. Here on Flicker is a lot of pictures of mine.

http://www.flickr.com/photos/24589494@N00/

 

[Silvertip]

Re: single/tandem trailer 18' boat

Probably not overkill woosterken. It appears those are 10-inch wheels and tires and unless they are load range E (1505# capacity @ 90 PSI) I would say you have a very adequate setup, but certainly not overkill. Just from the picture, it would appear the axles are 2000/2200# units so that alone says 4400 pounds max. Then the tires enter the picture (xxxx times 4). The boat looks heavy so if you consider the trailer weight, boat weight, accessories and fuel, engine, battery(ies) you might be surprised at the outcome. Those of you hauling in excess of 3500# on a single axle trailer should take heed. If you have five bolt hubs, they are rated at 1750# each for a total of 3500#. Likewise, the axle has 3500# capacity because of the spindles and the bearings (1-1/16 outer and 1-3/8 inner. Hubs with greater capacity have larger bearings, require a larger spindle and the tip off is that the hubs will have six bolts. Yes, lots of people haul things in excess of what the trailer is designed for and get away with it. Just don't get involved in an accident because when the courts are done with you someone else will own your stuff.

 

[woosterken]

Re: single/tandem trailer 18' boat

yes your right,the sticker says (mfd 5/74) same year as the boat.trailer weight is 780#
GVWR 5280# with 800-10-8pr tires
but then it says maximum load capacity with 800-10-8pr tires is 3500#
when I got it,it has 20.5x8.0-10 e tires on it (90psi cold 1535 #load rate) 4 lug wheels
it pulls like a dream
it also says GAWR FRONT and GAWR REAR but list no weights.
I guess you just divide the 5280# by 2 for the 2 axles to get the axle rate right ?
the boat has a 120hp mercruiser I/O
1 battery
18gal gas tank

woosterken

 

[Silvertip]

Re: single/tandem trailer 18' boat

Since you downgraded the tires from the 10 ply (load range E) that were on the trailer, you also downgraded the GVWR of the trailer. This is why it is so important to replace tires with exactly what was on the trailer originally, or with an upgraded tire. Even if you upgrade the tire to carry a heavier load, the axle itself remains at the same GVWR. On a tandem trailer the front and rear axles should carry the same load. The key to determining axle capacity is really in the bearings. If the axle takes 1-1/16 inch inner and outer bearings it is a 2000/2200# axle. If it takes 1-1/16 outer and 1-3/8 inner it is a 3500# axle. Those are the standard axles but there certainly are exceptions. On torsion axles however, to get exactly the same weight on each axle, the trailer must be towed perfectly level. Any time any one wheel goes over an obstacle like a curb or drops into a hole, that wheel or axle can unload or overload if the trailer is at or near it's maximum. I've seen these trailers make a turn front one street to another that has a relatively sharp drop in elevation and the front wheels actually come off the ground. The weight carried by that axle is now sent rearward and onto the tongue.

 

[woosterken]

Re: single/tandem trailer 18' boat

ok,thank you for all the info
the p/o just packed the bearing and put new bearing buddies on it the day I picked it up but didn't tell me the size of the bearings.
I have only used it a few times due to health

woosterken

 

[Titanium48]

Re: single/tandem trailer 18' boat

6000 lb trailer axles are also available and not terribly uncommon, so a single axle trailer with a load rating in the 5000 to 6000 lb range is possible. 5000 lb is possible with 15 inch wheels, 6000 lb would need 16 inch wheels.

 

[Silvertip]

Re: single/tandem trailer 18' boat

There are exceptions as I said, but a 5000# axle will generally have a six bolt hub and wheel. It will also have a bigger spindle which requires larger bearings as indicated in the sticky at the top of the page. I'm not contending that higher capacity axles are not available. I'm trying to inform people of how to tell the difference so they don't slap big tires on an axle that can't safely carry the weight.