20 foot seacraft power options

[rbandy]

Hello, I'm glad to have access to such a wealth of knowledge. I am creating a 20' classic from a bare hull and liner that I acquired and I'm trying to create a machine that is unique and usefull. I will be finishing the build with custom console and leaning post and all the work will be directed towards weight savings for efficient use. I have raised the floor to try and maintain a self bailling cockpit and I've acquired a 60 gallon tank that I will mount as far forward as possible. I have been pondering all the different power options and see that alot of the people on this forum prefer the 140 Suzuki 4 stroke. I was actually thinking that an older 150 merc would be ideal because of its light weight. I'm trying to do this on a budget and use older technology for power. Something cheap and readily available. I have (2) 3 cylinder OMC 70's, 2000 model, as a matched pair. The weight of this pair is close to the 140 Suzuki 4 stroke. Will I receive benefit or additional lift from two wheels? Has anyone here powered with twins? My concern is that 500lbs is too much weight for the boat to plane at slow speeds. I haven't had or ridden on these boats before.
Any imput would be appreciated.