will my 17ft boat fit on 18ft trailer?

[rhillcity]

I have a 17ft boat and a 18ft trailer ,the width is fine on the new trailer but it is a foot shorter than the old trailer. the old trailer was 19ft,and the new trailer is 18ft, i have a 4ft tongue to move the bow stop up a foot to make up the distance, but will this be to far forward for tongue weight or will it be in the limits.also can the transom hang off the bunks or roller, and how far? I cannot move the Axel forward everything is welded

My boat is a 66 model, 17ft Cobia with 85hp outboard engine

 

[109jb]

Re: will my 17ft boat fit on 18ft trailer?

You may be able to move the axle forward to compensate. Depends on the trailer, In many the spring hangers are bolted on and can be moved easily. On others they are welded.

 

[Willyclay]

Re: will my 17ft boat fit on 18ft trailer?

Welcome to the iboats.com forum. The experts here can help you solve any problem with a boat, motor and trailer. Pictures help a lot. Good luck!

 

[rhillcity]

Re: will my 17ft boat fit on 18ft trailer?

All the springs and axle are welded and I can't move I can move the bow stop up one foot and lengthen the bunks

 

[Silvertip]

Re: will my 17ft boat fit on 18ft trailer?

Proper setup of a boat/trailer combo has the stern of the boat flush with the tail end of the bunks. You move the winch post back to contact the boat. Now obviously that leave you a little light on the tongue but then you have a bunch of excess tongue length so remove the coupler and cut off a foot. Since you have so much extra tongue length, perhaps even more can be removed. Moving the entire boat forward just to get tongue weight means you also have to back into the water farther to load and retrieve the boat. If tongue weight is still an issue, you merely load more stuff toward the bow when you head to the water.

 

[Texasmark]

Re: will my 17ft boat fit on 18ft trailer?

Sorry, but I don't understand the post. You have a 17' boat that was on a 19' trailer and you are putting it on an 18' trailer and have to move the bow chock forward? One would think that the bow chock would move back 1', not forward if it was a trailer for an 18' boat.

Regardless, tongue weight is important in a trailer to help in suppressing trailer zig zagging, sway, instability, jacknife, (ha, loss for words on this one, just plain forgot......where the trailer violently moves from 90 degreees on one side, all the way over to 90 degrees on the other side and back and forth which takes up your lane and the lanes on either side of your vehicle....have seen it happen).

Proper tongue weight runs about 10% of the weight of the trailer and it's load and hitches are usually rated accordingly. On your boat, I'd guess it at roughly 2500 lbs which would allow you to place bathroom scales, which easily record 250#, under the tongue and measure it. Then like Silver said, if it's too light, load more in the bow of your boat, or mount your spare on the tongue immediately behind the bow chock.

I wouldn't fool with moving the axles unless it just had to be done and if the springs were on a sliding pice of angle iron that was bolted to the trailer's frame....like Dilly Trailers used to do.

One other thing, as Silver also said, a long tongue is in your favor especially on shallow ramps and also, when towing, the farther the axles are from the towing vehicle, the better the trailer resists swaying. So you actually may be loosing 1' from your 19' trailer and may notice the difference in these areas.

My 2c and over the years, I have adjusted half a dozen rigs or so.

Mark

 

[jeeperman]

Re: will my 17ft boat fit on 18ft trailer?

I have a 17ft boat and a 18ft trailer ,the width is fine on the new trailer but it is a foot shorter than the old trailer. the old trailer was 19ft,and the new trailer is 18ft, i have a 4ft tongue to move the bow stop up a foot to make up the distance, but will this be to far forward for tongue weight or will it be in the limits.also can the transom hang off the bunks or roller, and how far? I cannot move the Adelaide forward everything is welded

My boat is a 66 model, 17ft Cobia with 85hp outboard engine

Are the axle(s) the exact same distance from where the transom sits on both trailers?
If not, the difference might balance everything out and you will end up with the same tongue weight you had with the old trailer.

 

[109jb]

Re: will my 17ft boat fit on 18ft trailer?

I thought the same thing when I first read the original post, but if you read it carefully, I think he is putting a 17' boat on an 18' trailer, NOT a trailer made for an 18' boat, but a trailer with an overall length of 18'

 

[Silvertip]

Re: will my 17ft boat fit on 18ft trailer?

If that's the case, then that leaves one foot between the bow of the boat and coupler. Must not plan on making short radius turns. The key to boat/trailer setup as I mentioned earlier is to position the boat so the transom is flush with the end of the bunks. The rest either works or it doesn't and must be altered or adjusted as necessary. This is not usually a problem with a trailer "made" for a longer boat. But putting a boat on a trailer this made for a shorter boat means there will likely be too little room up front so there is a tendency to modify the trailer so the bunks extend farther back or they simply leave the boat hang over the bunks which is really tough on the hull. This puts the axle way too far forward and it becomes nearly impossible to get the correct tongue weight.

 

[jeeperman]

Re: will my 17ft boat fit on 18ft trailer?

I have a 17ft boat and a 18ft trailer ,the width is fine on the new trailer but it is a foot shorter than the old trailer. the old trailer was 19ft,and the new trailer is 18ft, i have a 4ft tongue to move the bow stop up a foot to make up the distance, but will this be to far forward for tongue weight or will it be in the limits.also can the transom hang off the bunks or roller, and how far? I cannot move the Adelaide forward everything is welded

My boat is a 66 model, 17ft Cobia with 85hp outboard engine

LOL, could be an 18ft trailer, yikes!!
But I read it as he has a 17ft boat. Which use to be on a trailer made for a 19ft boat.
Now he wants to put the 17ft boat on a new trailer meant for an 18ft boat.
And what is an Adelaide?

 

[cribber]

Re: will my 17ft boat fit on 18ft trailer?

Going on the assumption that it's a bunk style trailer moving the bow stop a foot forward so that your transom is fully supported by the bunks is a good idea. That said, you will increase you tongue what somewhat. Everything depends on what your tow rig can handle. As long as your tongue weight is in the 9-12% sweet spot of rated towing capacity you should be fine.

 

[rhillcity]

Re: will my 17ft boat fit on 18ft trailer?

I think I am going to extend the bunks out 1 ft to make up for the shorter trailer will the bunks be enough support for the transom with them hanging over a foot passed the last bunk support?

thanks

 

[Genonbamagirl]

Re: will my 17ft boat fit on 18ft trailer?

Load it, trailer it out onto a major highway, observe the consequenses and then report back. Ease up to speed so as not to spook any overly spooky people in the tow vehicle.

My guess is it will tow sweetly without a single adjustment. The way to check for that is to try it. THEN, if it does have issue, ask questions.

 

[Genonbamagirl]

Re: will my 17ft boat fit on 18ft trailer?

Bunks sticking out past the bottom following edge of the craft are of no consequence unless one encounters trailoring issues at high speed. Has one encountered trailoring issues at any speed?

 

[crackedglass]

Re: will my 17ft boat fit on 18ft trailer?

It sounds to me like he's most likely measuring the trailer tip to rear, so he most likely has a boat trailer meant for a 16' boat. The balance and final result will depend on the motor weight and how the thing is balanced or adjusted.
If the boat is hanging over the bunks, then I'd say yes, you need to make them longer so as to extend an inch or two beyond the boat's transom.
How much are they already past the last cross member?
You don't want the boat all the way up against the truck anyhow, but you do want some tongue weight. Maybe a few pics are in order here for some better advice?

 

[Silvertip]

Re: will my 17ft boat fit on 18ft trailer?

Thats not what he's suggesting. He's planning to extend the bunks past the last support not the stern of the boat. This becomes what is called in engineering speak "strength of materials analysis". If the bunks are 2x4's and have no support with one foot of the end, you have one foot of 2x4 on each side to support the heaviest part of the boat. Note that I said the heaviest part of the boat -- not the total weight at the stern. Weight is spread the full length of the bunk and whether the bunk is stressed or not on that last foot would need to be calculated. To illustrate this point, hold a 2x4 by the end (if you can). It would take very little force to push the unsupported end down. If you held it in the middle, it would take more force. Holding it one foot from the end would take more force. Chances are one foot will be ok. But the bending moment for the bunk is at the last support. If the 2x4 bows at that point, so will the hull of the boat.

 

[eli_lilly]

Re: will my 17ft boat fit on 18ft trailer?

I think I am going to extend the bunks out 1 ft to make up for the shorter trailer will the bunks be enough support for the transom with them hanging over a foot passed the last bunk support?

It depends on the bunks. I wouldn't do it with 2x4 or 2x6 sitting flat. An old trailer that I had used 2x6 laying flat hanging out about a foot and they warped. The trailers I have now both have 4x6 sitting on side and the bunks are cantilevered out 2 or 3 feet and they don't warp.

-E

 

[Willyclay]

Re: will my 17ft boat fit on 18ft trailer?

Agree with Eli. Typical around here is 4x6's. Good luck!