Saito .56 on mine running a 12x6 APC. Flys great with plenty of power. 50ft or less take off length in water. Great aerobatics and scale looking flight. I like the saito because it is very very reliable. You don't need any stalls in the middle of the water. However I have an OS .46 running an 11x6 APC in my T-34 and it's another great engine and it idles so low that you can see the prop. The .46 would work great in the seamaster as well.