VMR Gladstone Base: 07 4972 3333 Duty Controller: 0417 681 921

Many people complete a boating course, obtain a boat licence, and buy a boat, never considering that in many cases every boat trip begins and ends with a road trip. There is a lot to know and a lot to consider if you will be towing your boat to the water and back. We are going to talk just a little bit about some of the things you should be conscious of. Be aware that this is not an exhaustive list but should instead be enough to help you start thinking about whether you might have some blind spots in your knowledge.

Before we go any further, it will be helpful to understand some of the terminology used:

  • Tare mass (TM) – this is the weight of the trailer when it leaves the factory ready for sale.
  • Gross trailer mass (GTM) – this is the maximum mass that can be carried by the trailer’s wheels and in this case includes the mass of the trailer, boat, everything on your boat and everything in your boat.
  • Tow ball mass (TBM) – this is the amount of mass that is directed onto the tow ball.
  • Aggregate Trailer Mass (ATM) – this is the combined mass of the GTM and the TBM.

The first thing to figure out is just how much mass you can actually put onto your trailer. Locate the trailer’s compliance plate which will tell you the ATM and simply subtract the TM from this figure. The number you get is the maximum mass your boat, things added to your boat, things in your boat etc. can be in total.

However, it’s not that simple. You also need to consider the vehicle you are going to tow the trailer with. This means locating the compliance plate or consulting the manual for that vehicle and confirming that it’s maximum towing capacity is more than the ATM. You need to also confirm the maximum capacity of the towbar. When doing this, be aware that car manufacturers have been known to sell cars fitted with towbars that have a lower towing capacity than the vehicle itself. Also check the rating for the towball itself and make sure the TBM (ATM-GMT) does not exceed this figure.

Once you know the GTM you can also make a decision about brakes. If the GTM is between 750kg and 2000kg you must have an override brake on at least one axel. Between 2000kg and 4500kg, you will need brakes on all axels that are part of the tow vehicle’s braking system.

If you go over 4500kg, you are in heavy vehicle territory and should have the relevant expertise to operate a heavy vehicle. Likewise, if your trailer and boat exceed 4.3m in height, the width exceeds 2.5m or the rear overhang is more than 60% of the wheelbase (or 3.7m) you are towing an oversized load and should also have the relevant expertise to be doing this.

At this point many people are probably thinking that some of the weights involved in these calculations are hard to determine. You are absolutely correct! For example, a boat dealer might be able to tell you the rough mass of a boat, but they probably can’t tell you what the mass will be with fuel, food, drinks, and fishing equipment onboard. This is why you should consider loading your boat up as you normally intend to, or perhaps with slightly less weight to be safe, and heading to the nearest public weighbridge before going anywhere else.

If you have any questions about towing your boat, or anything else related to your boat, you can always contact Volunteer Marine Rescue Gladstone