How much does my boat weigh

[antonywardle]

A question that I've often wondered is how much does my boat weigh.

I found a calculation on the internet to tell me such a thing. I can't find it now

but it was you measure from the jockey wheel on the front of the trailer to your axel

and then put a set of scales underneath and write down the weight. Then move your

boat forward a distance and then weigh the boat again, plug it in to the calculator and

see what you come up with

so its:

distance(second weight-first weight)/distance you moved it

The second weight should be heavier, assuming you moved the boat forward.

Now I didn't do this, I actually moved my axle back because mine was pretty light so

I got 4053mm(76kg-15kg)/280mm

which means my boat weighs 882kilograms

My outboard weights 145kg and I have a 50 litre fuel tank if I assume there was 20 litres of fuel in

the tank, then that would weigh about 14 kilos. There wasn't much oil in so I'll ignore that

(Weight-density of petrol is about 737.22 kg/m3, which would mean a litre would way about 0.74 kg or 740 grams)

882-145-14= 723Kilograms

I guess the next thing to do is to go to a weigh bridge and then get the weight and sub-tracked 723 kilos from it

and I have the weight of my trailer.

My boat had all the gear on it except my rods. Its a 4.98 Safari Caribbean FG (its the one pictured in my profile pix)

Hows that weight calculation sound? I'm not sure if moving the axle is the same as moving the boat for the calculation

but I needed to do it. 15kg on the jockey wheel wasn't much fun when trying to work in the boat!

I can't find the website now that I got the calculation from but its an easy thing to do. I just used bathroom

scales when my wife was out!

Edited December 22, 2015 by antonywardle

[Fab1]

A question that I've often wondered is how much does my boat weigh.

I found a calculation on the internet to tell me such a thing. I can't find it now

but it was you measure from the jockey wheel on the front of the trailer to your axel

and then put a set of scales underneath and write down the weight. Then move your

boat forward a distance and then weigh the boat again, plug it in to the calculator and

see what you come up with

so its:

distance(second weight-first weight)/distance you moved it

The second weight should be heavier, assuming you moved the boat forward.

Now I didn't do this, I actually moved my axle back because mine was pretty light so

I got 4053mm(76kg-15kg)/280mm

which means my boat weighs 882kilograms

My outboard weights 145kg and I have a 50 litre fuel tank if I assume there was 20 litres of fuel in

the tank, then that would weigh about 14 kilos. There wasn't much oil in so I'll ignore that

(Weight-density of petrol is about 737.22 kg/m3, which would mean a litre would way about 0.74 kg or 740 grams)

882-145-14= 723Kilograms

I guess the next thing to do is to go to a weigh bridge and then get the weight and sub-tracked 723 kilos from it

and I have the weight of my trailer.

My boat had all the gear on it except my rods. Its a 4.98 Safari Caribbean FG (its the one pictured in my profile pix)

Hows that weight calculation sound? I'm not sure if moving the axle is the same as moving the boat for the calculation

but I needed to do it. 15kg on the jockey wheel wasn't much fun when trying to work in the boat!

I can't find the website now that I got the calculation from but its an easy thing to do. I just used bathroom

scales when my wife was out!

There's 3 weighs I'd be concerned about.The first is that the trailer is rated to carry the fully laden boat,the car is rated to tow the fully laden boat plus all gear and passengers in the car,and the down force on the towbar is within spec when the trailer is attached.Your rego papers or/and the compliance plate/s should have the weights.I'd fully load the boat with all gear/fuel and take it over a weighbridge for good measure if you haven't done so already.(You won't be the last one to be surprised)

The bathroom trick Is often used under the tow hitch to determine how much downforce is on the towball.

[antonywardle]

The trailer is a Tinker for a much larger boat.

I've change the wheels/tyres to be LT so they have no issues with the weight

The tow vehicle is a Prado. Max towed mass (trailer plus load) 2500 kg

Good point about the trailer papers, I'll take a look

Anyone know if my calculated weight looks about right?

[locodave]

Mate you need a degree for this haha!

I just stick to the weigh bridge, but I like how you are trying to work it out would be good to see how accurate that method is and then go weigh bridge.

[antonywardle]

thanks

I guess two trips to the weigh bridge will be required to confirm the maths.

One with the trailer and and one with the trailer boat, unless of course the

rego papers say the actual weight..

Its a bit of fun doing the maths, not that I'm suggesting maths is in anyway fun!

I'm also doing a degree at nearly 50 because my current place of work think

i need one.

[antonywardle]

I never did make it to the weigh bridge and now I've sold that boat.

With my new boat, I borrowed a mates bottle jack with a pressure gauge on it. 

You jack your trailer up in three places and then add the numbers up and that's your weight. Has anyone one here used one and how accurate did you find them? My new boat came in a 1600 KG

I might try with the maths above as my trailer has its weight on it, and eventually I'll take it to the weigh bridge and see if all three methods come up with about the same results.

 

[antonywardle]

@Mmg LT is a good idea. I think my old ones were  rated 950KG each

 

New trailer has four wheels and I've not actually checked them. Your post has reminded me that I need to do this.

Thanks!