Let me give you a quick rundown of how engines work since its pretty straightforward. For smaller rafts with under 100 foundations one engine will do the job, but you might want two anyway since it makes you go faster. As your raft grows youll need more engines, like two for up to 200 foundations and three if youre going bigger than that. Something interesting to know, the game stops counting after six engines but that's usually plenty even for massive builds

You'll need a 3 by 2 space with water access to place each engine, and make sure they're all facing the same direction or youll have some problems. Its actually smart to group them together since it makes refueling way less of a hassle. Biofuel is your best bet here, giving you about 45 minutes per tank which is way better than using planks

If your raft starts stuttering or moving weird, its probably one of a few things: either your raft is too big for the number of engines you have, your engines are pointing different ways, you left the anchor down, or you just ran out of fuel. Pretty easy to fix once you know what to look for, and keeping an eye on these things will save you some headaches later on. Keep in mind that even smaller rafts can benefit from multiple engines, so don't feel like you need to wait until your raft is huge to add more