210 Montauk Trailer Adjustment

[Ridge Runner]

I have a 2016 210 Montauk that I upgraded the engine from the stock Mercury FourStoke 150hp (455lbs) motor to an Evinrude G2 200HO (537lbs). I did not get a chance to tow this boat in its stock configuration. When towing the boat home from the selling dealer to my marina last spring, a 70 mile trip, the trailer would start to drastically sway when I started to go over 50mph. I didn't have time to address this concern last year and the boat on trailer are currently shrink-wrapped and stored at the marina for the winter.

In the upcoming two months I am going to be towing the boat from NJ to FL and need to address this concern. The trailer is the original BW Karavan tandem axle trailer and the tow vehicle is a 2015 Ford Expedition (factory equipped to towing 9,200lbs). My addition of all the components and fuel puts my total weight at ~5,400-lbs.

Where should I start from an adjustment perspective on the trailer?

Should I purchase a trailer tongue weight scale, about $140, and start by moving the axles back by 2-inches and then test it?

As you can see in the pictures the axles are already rather far back on the trailer. I have read that tongue weight will increase an average of 10 to 15-lbs. per inch of moving the axle back.

Any advise on what you think my first adjustment should be and the best way to get my combo correct would be appreciated.

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[ConB]

I would try to move the winch stand a head 6" and see how it behaves.

You want 7-10% of the tow weight on the hitch of the tow vehicle.

Con

[Jefecinco]

When you say Boston Whaler trailer do you mean a Karavan trailer normally sold with late model Montauks? If so, it is very likely the trailer is correctly set up for towing.

Before doing anything drastic like moving axles make sure your trailer and Expedition are correctly set up for towing. I would be certain the trailer tires are correctly mounted, balanced and inflated to the maximum recommended sidewall pressure. I would also inflate the Expedition tires to the max pressure for towing. Ensure the hitch ball and tongue receiver are the same size. Check the winch strap is completely tight and the bow fully forward on the trailer winch post. If you are not using trailer tie down straps to secure the transom to the trailer do so. Get purpose made robust straps for tie downs. I believe the ratcheting type tie downs work well. After towing a few miles pull off the road and check the winch and tie down straps for tightness and adjust as needed. New straps often stretch when used for the first few times.

Some trailer oscillation is experienced even when a trailer/tow vehicle are set up properly. Strong gusty side winds, uneven pavement joints and very rough roads can induce oscillation. When I towed a longer tandem axle trailer I found a momentary push on the brakes would stop the process.

If you are unable to stop the oscillation consider consulting with Boston Whaler or Karavan before adjusting the axle or winch post settings.

[Ridge Runner]

I am very apprehensive about moving the winch post forward which would pull the boat up the trailer and change the way it sits on the bunks supporting the hull. Butch - yes it's the factory Karavan trailer, the trailer tires where about 2psi off the max, I run my Expedition tires at 44psi - 50psi is max, the winch strap was tight and I always use rear tie down straps. The rig attached to the truck is very level. I have towed FL to NJ and back many times with a different rig so I am pretty experienced in towing. I was very shocked that this set-up swayed to much when I went over 50mph. To the point that I was a bit concerned about applying the brakes when the sway started and just let the rig slow down naturally when it started to sway.

[ConB]

Assuming the sway is because of light tongue weight, The boat needs to move forward on the trailer or the axles need to go rear ward. Or put a few cases of beer in the bow of the boat.

In the picture the transom looks like it is over hanging the bunks rear ward. I would move the boat ahead so the transom is in line with the rear cross member of the trailer. Unless your boat is weird bunk fit should not change. If that didn't fix the sway then the axles and or beer thing.

A bath room scale may go high enough but weigh at coupler not tongue jack.

Con

[jimh]

TO MEASURE TONGUE WEIGHT: find a certified truck scale in your area. Tow the boat to the certified truck scale, and weight all the axles; then re-weigh without the trailer. For details, see my article about using certified scales to find tongue weight:

Boat Weight From Certified Scale
http://continuouswave.com/ubb/Forum1/HTML/016667.html

This will only cost about $10. You get much more information than just tongue weight.

Even if you could just measure tongue weight, it would not be particularly useful because you would not know the total towed weight.

The notion when towing a trailer that the tongue weight must be ten-percent of the total towed weight is not particularly a hard and fast rule that cannot ever be ignored. The behavior of the trailer with sway and other motion is probably quite a complex system. The tongue weight is only one factor.

Another consideration may be the axle alignment on the trailer: are they both square and parallel? Measure the distance from the trailer tongue to the same points on each of the axles. The left-right axle distances to the tongue should be the same.

[jimh]

Does your rather modern 2015 FORD Expedition have any sort of trailer-sway automatic control? If the vehicle is automatically trying to correct for what it detects as trailer sway, it could actually be generating more trailer sway. Applying corrections to the steering when the trailer starts to sway can often induce more sway, not less. If that is being done by an algorithm, it could be not perfect for a particular boat trailer set-up.

[jimh]

...I have read that tongue weight will increase an average of 10 to 15-lbs-per-inch of moving the axle back...

To understand weight distribution on a trailer, read

Trailer Hitch Loads
Considerations and Calculations
http://continuouswave.com/whaler/reference/trailering/trailerCalculations.html

If you read the article, you will find you can download a computer executable program to make the calculations described.

[jimh]

Tongue weight can be changed by two methods:

--the position of the boat on the trailer is shifted forward or backwards; moving the boat toward the tongue increases tongue weight; moving the boat away from the tongue decreases tongue weight; or,

--the position of the boat on the trailer can remain stationary and the position of the axle or axles on the trailer can be moved; moving the axles farther from the tongue will increase tongue weight, and moving the axles closer to the tongue will decrease tongue weight.

Of the two methods, it is generally easier, faster, and much less work to move the boat position. With regard to the boat position on the trailer, there are general limits:

--the transom of the boat should not be located so it is aft of the bunk supports of the trailer, that is, the transom should not be hanging out beyond the bunks; and,

--the bow or any bow pulpit or other projections should not be so far forward on the trailer that they could interfere with the towing vehicle; for example, you should be able to open the door or truck bed gate without hitting the trailer or boat. (On my boat and trailer rig, the opening rear door of the SUV just misses the long bow pulpit extending from the boat by an inch or two; the boat is about as far forward on the trailer as practical.)

If you decide that the trailer axle position must be adjusted, you should unload the boat from the trailer to facilitate working on the axle position.

As CON mentioned, an expedient for adjusting tongue weight is to add weight to the boat, assuming there is plenty of margin available in the tow vehicle maximum towed weight rating. Two 50-lbs sand bags in the very farthest part of the boat bow should create an increase in tongue weight which could be then assessed for its effect on the trailer tendency to sway.

Although not completely clear, in the small image of the boat and trailer it appears that the boat transom is just aligned with the end of the trailer bunks. If that is true, then the boat position on the trailer looks correct with regard to the bunk position at the transom.

Before making any change in trailer or boat positions, you should find the present tongue weight and the present total towed weight with good accuracy.

[Ridge Runner]

Thank you Jim for all the information and insight. You are correct the stern of the boat is perfectly even with the end of the bunks. I do think the cause of the sway is that the E-TEC is positioned a bit farther aft than the original Mercury outboard. Weighing about 100-lbs heavier (the E-Tec power head also holds about 2.5 gallons of XD100 oil), plus the fact the E-TEC has a farther set-back and pivot point (almost like a 5 inch jack-plate) is probably causing more of a cantilever effect. As you can see in the pictures below, the centers of gravity of the powerhead are different, the Mercury powerhead is positioned more towards the interior of the boat compared to the E-TEC, changing the center of gravity. I have no-doubt that the standard factory set-up towed correctly.

Putting some weight, with sand bags, in the bow is a great idea to get a sense of how much additional tongue weight I need.

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[ConB]

Before the engine change, did the Montauk tow okay with the Expedition?

Now I am wondering about the aerodynamic effect of a T-top when towing.

Con

[Rinoue]

I tow my 210 Montauk with factory Karavan trailer several time a year with my Toyota Tundra without any sway.

Probably the extra weight of the engine and the set back is causing the sway.

[Jefecinco]

If the sand bag method determines that increased tongue weight is needed and the winch post is moved forward a few inches a test trip can determine if the adjustment solves the problem. After a final position for the winch post has been determined it will be relatively easy to adjust the bunks forward so the hull is properly supported. I believe the bunks on the Karavan trailer under our 190 Montauk are attached with galvanized lag screws.

Relocating the axles is a chore and tandem axles are more so. Very careful measurement and placement is necessary to ensure the axles are precisely aligned for straight travel and spaced exactly as original so the fenders will fit well when reinstalled. The bigger problem is ensuring the placement will be correctly established when completed so it won't have to be done again if it is not right.

[Dutchman]

If increasing [tongue] weight doesn't work, what about adding [a weight distributing hitch with an anti-sway accessory item]?

[jimh]

Dutch--you pointed to a weight distributing hitch to which some sort of anti-sway accessory has been added. I have never seen this gear used on a boat trailer before. Here is a link to the manufacturer's page that describes it:


http://www.curtmfg.com/Category/77/Sway%20Control

Do you any first-hand experience with using this device on a boat trailer?

The instruction sheet is here:

https://assets.curtmfg.com/masterlibrary/17200/installsheet/CM_17200_INS.PDF

Can you explain how these work? If the device inhibits the motion of the trailer behind the boat, how do you make a tight turn with the trailer, like backing up for a ramp, with the sway control device in operation?

The first thing that stands out to me is the clear warning:

WARNING: The sway control cannot be used on trailers
with surge brakes. Do not speed up if sway occurs; sway
increases with speed. If sway continues, stop the vehicle
and inspect all towing equipment until the cause has been
determined and corrected. Trailers should be loaded with
heavy items on the floor, in front of the axle. The load
should be balanced side to side. Tongue weight should be
10-15% of gross trailer weight for most trailers. Insufficient
tongue weight or tail-heavy trailers can cause sway. When
towing in slippery conditions, such as wet, icy, gravel or
snow covered roads, the sway control must be removed.

In order to discover if this device could be effective to the boat trailer, apparently the brake system cannot be a surge brake actuator system.

Also, the kit includes a "weld-on tab". Where do you weld-on the tab? It sounds like a rather serious modification is needed.

Also, adding all of this gear to the trailer at the tongue would increase the tongue weight. How would you know of the improvement came from the unusual anti-sway device or just from all the added tongue weight?

[Ridge Runner]

Interesting enough, today I received Boston Whaler Service Bulletin #BW#17-027:

"Your 2018 210MT is involved in a service campaign to verify the winch/roller stand position."

"Dear Customer:

Boston Whaler, in conjunction with Karavan Trailers, has determined the some 210MT winch/roller stands may be positioned out of specification and could reduce the tongue weight. Poor trailering performance with reduced tongue weight could result in fishtailing and unsafe towing conditions. In response to this, Boston Whaler has initiated a field campaign to verify the winch/roller stand position and adjust when necessary.

Our records indicate that you purchased your 210MT from Hance & Smythe and the serial number falls within the affected range of this notification. Due to the nature of this service, the work must be completed by a certified Boston Whaler dealer."

With my E-Tec's setback this must have compounded the fishtailing.

[Ridge Runner]

Taking Jim's advise; I proceeded to get my boat & trailer weighted. The complete rig weight was certified at 4,970-lbs.

I tested the accuracy of the Sherline LM 1000 Trailer Tongue Weight Scale that I noted in thread: viewtopic.php?f=6&t=3381 The scale has spot on accuracy. Using the scale to discover my tongue weight I was very surprised to find out my tongue weight was only 220-lbs or just 4.4% of the total weight.

Tongue weight at 220-lbs is a far cry from the recommended 10% of the total weight or about 500-lbs. Again following Jim's recommendation, I added weight to the bow of the boat until the scale read 500-lbs. I had to add 450-lbs of sand bags to my anchor locker and fish box to attain the 500-lb tongue weight. I then went for a test drive and the rig towed much better. Due to my time frame in having to tow from NJ to FL next Wednesday I will probably just keep the sand bags in the boat.

The long-term fix has to be moving the axles back on the trailer.

Needless to say I was very shocked at the original 220-lbs tongue weight.

[Dutchman]

Dutch--you pointed to a weight distributing hitch to which some sort of anti-sway accessory has been added. I have never seen this gear used on a boat trailer before.

Do you any first-hand experience with using this device on a boat trailer?

Yes I have used such a boat trailer set-up, but on a much larger and heavier(32ft) boat. And yes you can not back up with a friction induced type anti sway-bar as shown. I always remove my anti-sway bar [before] backing up and I used to disconnect trailer power.

I still use thw system (shown in my first link) currently while pulling a camper trailer with a much smaller tow vehicle. Yes there is a regular 2-5/16-inch ball with a smaller (about) 1.5-inch ball next to it for the anti-sway bar which also has a ball mounted to the A-frame of the trailer. I use a two finger tight method to set my friction and it has proven me well.

I always had and have electric brakes on my trailers that self adjust when backing up (and not locking up).

Yes; you are right. I never launched the larger boats. I always had them lifted off the trailer with a boat lift and lowered in the water, so I have no idea how that would act on a steep slope.