Trailer seems to fishtail

sullmate · Nov 12, 2011

Hi All,
I have a 1994 Searay bowrider, 18 ft with a 135 HP mariner V-6. My trailer is a 1993 Shorelander - galvanized (2700 lbs capacity.). Boat & motor weigh about 2000lbs. Gas and battery add about 225 lbs. The trailer weighs 410 lbs. empty. The total weight is about 2700 lbs. There is 215 lbs on the tongue or about 8% of the total weight.
At highway speeds (55 mph) the rig wants to fishtail. Should I increase the weight on the tongue? If so, what % of the total weight should I put on the tongue? I can't move the winch (crank) back anymore towards the tongue.
Please advise.

sschefer · Nov 12, 2011

Re: Trailer seems to fishtail

More tounge weight should help some. You could consider moving the axle back a little if you can't move the boat forward on the trailer. Does it sway all the time or just on bumps and then straighten back out again?

tswiczko · Nov 12, 2011

Re: Trailer seems to fishtail

What are you pulling it with?
Tongue weight should be about 10%
Get an accurate weight on the rig you can usually get it done any where they have a scale (quarry,scrapyard,etc)
also other things have a factor on how it is towing like when it is hooked on the ball does the trailer sit level or is the front elevated?
What is the condition of the tow vehicle? have you checked your tie rods?

I had a similar problem, replaced a worn tie rod and it went away

smokeonthewater · Nov 12, 2011

Re: Trailer seems to fishtail

the general rule of thumb for tongue weight on a trailer is 10-15% but at 8% you are very close and I'd think it is unlikely that tongue weight is your issue..... More tongue weight might likely stop the swaying but I suspect that there may be something else causing this issue..... Look at your tires.... are they inflated to max pressure? are they trailer tires and are they rated for the weight they are carrying? are they worn oddly IE outside or inside edges or cupped? Have you actually weighed the trailer and tongue weight or are you just estimating?

If you DO decide to increase tongue weight, can you move the trailer axle toward the rear?

sullmate · Nov 12, 2011

Re: Trailer seems to fishtail

the boat seems to fishtail all the time at 55 mph or higher

sullmate · Nov 12, 2011

Re: Trailer seems to fishtail

i am towing with a 2008 chevy trailblazer which has about 5000 lb tow limit

sullmate · Nov 12, 2011

Re: Trailer seems to fishtail

tires are inflated at the 50 psi limit. tire size is 215- 75-14. tires are 2 years old and in good shape. I think i have to move the axle more towards the rear of the trailer. The question is how much do i move is at a time.

halfmoa · Nov 12, 2011

Re: Trailer seems to fishtail

Be very, very careful moving weight foreward or backward. Adjust in small increments and slowly build speed after every adjustment. On the recommendation of a fellow racer we moved weight foreward on the trailer and had the trailer wildly fishtailing from one set of wheels in the air then the other and nearly rolled it on the interstate. We only moved the car about 8 inches forward.

"The straps work!" (nervously wipes brow and checks underwear)

joewithaboat · Nov 12, 2011

Re: Trailer seems to fishtail

As others have stated if you truly have 8% currently, i would look elsewhere for your problem. Don't underestimate the condition of things on the tow vehicle and how it might influence the trailer. Tires, shocks,struts,suspension etc.

Make sure your weights are accurate once you are sure of tow vehicle condition.

In the past i have had trouble if the tongue is not level, may need dropped or raised hitch. Also trailer tires and their rating/condition.

Good luck!

Maclin · Nov 12, 2011

Re: Trailer seems to fishtail

Wheelbase of the tow vehicle is a factor also. Shorter wheelbase vehicles towing a trailer with a relatively short toungue-to-axle distance (relative to the vehicle wheelbase) will experience this even with the 10% tongue weight. The longer the distance from the trailer coupler to the first axle the more stable a trailer is regarding left-right movements, and thus less tendency for sway. If you have a short trailer then even with the toungue weight "close" the sway potential is higher. Factor in a shorter wheel base vehicle and the sway potential is increased.

Can you borrow another tow vehicle and try it then? That may be a quick way to detect whether or not the wheelbase is a factor.

Also, can you post a pic of your rig from the side? That may shed some light on the relationships between all of the touchpoints.

JerryIrons · Nov 12, 2011

Re: Trailer seems to fishtail

I would try adding some weight to the tongue and take it for a drive to see what happens. I had an old coleman popup trailer that would sway at speeds above 60mph. I took a heavy chain that I used for hauling trees out of the ground, wrapped it around the tongue and it hauled just fine after that. If you add weight and it still hauls bad, then you can cross of tongue weight as the problem.

airshot · Nov 12, 2011

Re: Trailer seems to fishtail

Along with all the other suggestions, which were very good, you might check to see if the axle is square to the tongue. Make sure tongue is straight and not bent! Then use a tape measure to check and see if an equal distance from both sides of axle to a common point of measure near the reciever. I f the axle is not square that will cause the trailer to not track straight and cause fishtale problems at high speed. Never hit the brakes when a fishtale occurs as this can be disastrous, take your foot off the gas and slow down easy, be sure not to overcorrect. Been towing for 45+ years and have seen it all. Good luck in your findings.

Airshot

zopperman · Nov 12, 2011

Re: Trailer seems to fishtail

I'd also make sure that the tongue is level.. with your hitch... for all we know he has a 5" drop ball and the trailer is pointing downwards

cyclops2 · Nov 12, 2011

Re: Trailer seems to fishtail

Sure hope he does not have the boat bow pointing up a lot. Had a friend get a boat trailer setup like that. tiny trailer wheels high gitch on tow truck. The wind whipped the crap out of that rig. Finally got a dropped hitch. O K now

Can not be a wrong sized ( SMALL ) hitch ball.

Did you tow other trailers OK ??

Need to go to a Recycling place with great scales. They will tell you something interesting ?? You are guessing on the actual weight. Throw in abunch of stuff that you normally put in the boat on trips.

I do not know of anyone who can lift a trailer tounge & come close to the real weight. Weigh that too. Always better to be over by 5 %. Then under by 5 %.

26aftcab454 · Nov 12, 2011

Re: Trailer seems to fishtail

try moving heavy stuff in the boat forward ob the axle if you can.

smokeonthewater · Nov 12, 2011

Re: Trailer seems to fishtail

you can figure the amount of tongue weight you will get with a tape measure based on current % and current measurements (although you will need to actually weigh once) but my brain is tired and I don't feel like figuring the formula..... seems like something Bruceb58 would enjoy figuring out

If it were me I'd move the axle back a foot and head for the scale.

Fed · Nov 12, 2011

Re: Trailer seems to fishtail

Are you new to towing sullmate, maybe what feels like a fishtail to you would feel normal to someone else?

You weights seem pretty good to me.

Does it happen when your pulling hard, normally fishtailing from a bad setup happens backing off going down a hill, it will also make your knuckles go white, your eyes bulge and your heart rate go through the roof.

Scott Danforth · Nov 12, 2011

Re: Trailer seems to fishtail

move the winch post and boat forward a few inches to get more tongue weight

besides 10% tongue weight, you want the CG of the loaded trailer 6+ inches forward of the axle.

etracer68 · Nov 12, 2011

Re: Trailer seems to fishtail

I have to add my .02. My opinon would be the trailer is not level, either way up in front or way down,and maybe boat is not level on the trailer too. I would like to see a pic of the rig hooked up from the side.

cyclops2 · Nov 13, 2011

Re: Trailer seems to fishtail

Bingo !!

Trailer seems to fishtail

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