What tongue weight should I try to achieve?

boatster_sr4 · 25 January 2006, 00:33

I just got a really nice 18' aluminum trailer for my new sr5.4 . I was setting her up and found the tongue weight to be quite heavy, probably 175-200 lbs.

Well I haven't put the motor on the transom yet either. I can actually adjust the axle forward or backward on the frame. My question is, what is an ideal tongue weight for a sr5.4 with a 1996 Johnson 70 ( 113 kgs )? Is there supposed to be a percentage value of the total boat+trailer weight on the tongue? 10% ? 15% ?

codprawn · 25 January 2006, 00:40

A lot depends on the vehicle you are towing with - the car handbook usually tells you the range you should have.

If it is a big vehicle like a Land Rover or pickup truck etc then you can have a lot more than a normal car.

limeydal · 25 January 2006, 01:35

Boatster,
5% to 7% .as a guide.
So make sure you have the engine fitted and tank filled. Then off to the nearest weigh bridge.(edco do it for about $12.00 ) Found that easier and more accurate than trying to add all the weights up

After you do the math to find what you should have, just put a board on a bathroom scale and put the jockey wheel on to see what it actually is.
Mine was way out when I first towed it to the Bay ,so when you have the boat in the water take the opportunity to move the axle forward a few inches a time. Easy enough to do, as just loosen the U bolts and kick the axle forward .
I had to move mine forward about a foot to get a correct tongue weight of about 110lbs for my XS
cheers Dal

dctucker · 25 January 2006, 01:40

Funny, I was just researching this last night, as I may add a bolt-on modification to my trailer to allow me to load a 700# sailboat above the RIB. I'd most likely add brakes to the trailer if I do this. Iboats trailer forum is full of opinions, rangeing from 5% to 15%. In the end, the "consensus" answer was boats are different from other trailers and 5%-10% was good. Higher end of the range (or up to 15%) would do more to eliminate tail wagging at highway speed, it the tow vehicle could handle the higher tongue weight. Mine is probably too low, as I can easily lift it by hand, but I've yet to tow the boat more than 1-2 miles at a time. I should move the boat forward on the trailer a few more inches rather than adjusting the axle.

It seems the preferred way to measure actual tongue weight is on a certified vehicle scale, with the boat loaded as it will be pulled (fuel, battery, gear, etc). Park the rig so the trailer is on the scale, but the tow vehicle is off. Measure weight. Uncouple the tow vehicle with the trailer jack on the scale and re-weigh. That way you get the actual total weight of the trailer and how much is actually being carried by the tongue. Do the math to get the %. Adjust trailer/boat as necessary.

boatster_sr4 · 25 January 2006, 03:11

Ok. Thanks guys

. Seems like I need to put the motor on back as I just dead lifted the tongue tonight and its actually about 250# probably. I moved the boat much further up the trailer for garage stowability and so it is about 16" more forward than design. I think without the motor on, the tongue weight is really exagerated but even if I do put it on it'll be much more than 7% on the tongue.

My Mitsubishi Montero has a really soft suspension so right now the tail drops a bit. I think the trailer axle will need to be moved forward at least 1' even with the motor on.

limeydal · 25 January 2006, 23:35

Boatster,
just make marks with a permanent marker on the axle U bolt brackets on both sides of the frame before starting.
That way you can see how much affects the tongue weight by moving say 3" a time.More importantly you can make sure you you move the axle the same amount on each side ,so it keeps it square to the frame.
CA boating have a good resource if you havn;t checked it already
http://www.dbw.ca.gov/Publications.asp

They do a free boating safety course book with all the basic info; in.(you dont have to do the exam) but its a good resource.
cheers dal

CAH · 26 January 2006, 04:59

This might sound strange but we used a bathroom scale to measure tongue weight. We took the boat down to the local launch ramp and made all the adjustments in the parking lot.

limeydal · 26 January 2006, 06:05

good idea!

As long as you know the all up weight;you could fine tune like you described.
cheers Dal

boatster_sr4 · 26 January 2006, 09:19

Thanks for the link Dal.

CAH, thats a great idea for the scale. I'll have a go with that. I think I can get a good estimate of the total package weight +- 150 lbs I think. I've literally torn the boat apart for now so maybe I can weigh pieces individually and add it all up. I should take pics and do a slidestory

CAH · 27 January 2006, 04:58

If you have space on your trailer bunks try moving the boat fwd or aft on the trailer, this could save you from moving the axles. A couple of inches\cm can make all the difference.

Pacific Trailers in Chino may have answers to some of your concerns. http://www.pacifictrailers.com/

Some additional quotes from http://www.sandiegofishing.com/buddydb/

Tongue weight should be determined by trailer and hitch manufacturer. Too much, it will sway. Overload the hitch rating. Too little, trailer will sway while towing on level ground. The ball height needs to be figured into the over all mix also. Any trailer will have a recommended ball height. Follow that height as close as possible.

...the tongue/hitch alignment and load is critical. I wuz presuming (again) that you had it level and loaded out - back to basics, homey. Park the rig on a flat lot and step back and look at it - level vehicle and very slight down angle on the tongue is what you want. Adjust your hitch height (primary) or redistribute the load (secondary) to get the angle without exceeding your tongue weight rating of either vehicle or trailer. Normally this is 300 to 500 lbs. Ideally you want approx 2/3 of total load at or just ahead of the axle (some folks say centered) - now you can start thinking about altering the suspensions. Presuming (again) that your trailer axle(s) and vehicle axle(s) are aligned, too stiff on the trailer suspension will make it hop and too soft will make it sway.

Good Luck