You can substitute plaster or Portland cement or that fake chocolate stuff Cosby used to sell. Any liquid that will harden.
ha ha ha , all the tricks of a trade long lost!
Meanwhile I got the fright of my life a couple days ago.
I got the boat out for its bi annual startup n battery charge "sheesh thats 6 months between drinks" and came outside after a feed and found the young bloke sitting in it and going through my old tackle box's, he was finding lures n plastics, some not even opened, his excitment was obvious, couldnt even raise a smile or even look at the camera LOL, His mate stayed the night and we had an arvie fish in our local river system, saw lots of bust ups on the surface but I then remembered why I gave this away, very hard to get them to actually take the lure LOL, we came home cold and empty handed but its only a 1 minute drive so all was good, no fish meant KFC ha ha ha !
I Built n painted "Kiona" myself, it was a half cabin off shore fishing boat and the previous owners removed the top half to make an open style prawning boat, they didnt know what they were doing and I completed the task over a 2 year period! the boat n trailer cost $800, the 60 Evinrude E-tech cost $4k and I was the third owner, its a 2006 and comming up 350 hrs! it had 275 when I brought it in 2012. averaging 7.5 hrs per yr over 10 yrs LOL, needless to say its only a family boat these days but things change rapidly, hes into fishing now!
You can see the BMX ute is still not finished, after the bathroom theres still architrave and odd jobs on the house so its still getting put to work, Jeeeez its worth its weight in gold at the moment