engine will not crank, trim doesn't work

[rcrouch620]

I decided to do some boat maintenace before taking it to the mechanic to cut down on the cost.I have a 1999 5.0L mercruiser- carberated model with an alpha drive. I found the electric fuel pump humming, but no fuel coming out. I removed it from the boat, tried it off the boat and it will not pump. I installed a new fuel pump. I tried cranking the boat, and it barely cranked.I hooked charger up to new battery from bass pro shop and let it charge at 35 amps for several hours. I tried to crank boat, and the starter just clicked. I turned upthe charger to start( 200 amp) and tried starting the boat, nothing, no click, nothing. I have intermittent power to the gauges,sometimes the gauges bump when I turn the ignition key on, sometimes they do not,they act like they are not getting any power. The last time I tried to crank the engine the fuel needle bounces all over the place,and the starter didn't even click and I cannot trim up the outdrive up or down. I do have gauge lights, bilge blower, horn etc so I know power is coming from the battery. It just seems like anything that has to do with the engine is not working. I am thinking I might need to clean all the connections. I had a similar problem a few years ago, found the ground wire to my engine had a break in it, sometimes everything would work, other times was like having a weak battery. Any advise from you guys would be greatly appriciated before I go tearing everything apart.I have the clymer mercruiser manual and have looked at the electrical schematic, it looks simple, just hard to find the locations on the engine.