Lose extreme weight in boats from 1990?

Hi

Thinking of buying a 10-12 meter fiberglas motor boat from 1988-90 with a very big engine like 2 x 300 hk and almost 10 tons (10 000kg) that has NOT been renovated except the engines. Similar modern boats have almost half of the weight.

Because of the extreme fuel consumption (like 2 x 35L/h) at 25 knots cruising speed, and because it’s old I have some thoughts of making 100% completely new interior from the hull and up.

My plans are to use modern material and lose substantially weight which makes the boat substantially faster and substantially more fuel efficient.

1. This is a very stupid question but where do all the weight on those boats come from? (-thick construction wood, thick fiberglas, kitchen countertop in stone and so on and so on?)
2. It would be interesting to hear any thoughts if it’s possible to loose weight on an old motor boat?

One boat example below:

Cranchi mediterranee 40
10 tons
Cranchi Med https://www.boat24.com/se/motorbatar/cranchi/cranchi-med/detail/419546/

 

And how much weight do you imagine you can lose ? I doubt that you could strip out enough "unnecessary" weight to make any appreciable difference to your fuel consumption. Do you have an example of a similar size modern boat that is half the weight ?

 

Someone that wants a 10/12m boat and wants to spend a truckload of money to save 50lts/hr

Just kick it back to 6knts and you've achieved the requirement!

 

throw that TV away first thing you do!

 

You can't achieve a weight loss goal and if you did; the boat would float above her lines and possibly perform badly.

 

A stone benchtop ? Seems a bit much.

 

One thing you can do is install a fuel meter. This would help you find the sweet spot.

For a planing hull; it is just off the hump generally, so you can also go by feel. Take it up on plane and back it off so she doesn't sit down.

Most likely, you are running too fast.

 

Cranchi boats are not really heavy for a cruiser. If you want light weight, a better choice would be something like a Fountain, Wellcraft Cigarrette or other performance boat with minimal interior.