I recently bought a 1985 Chris Craft Scorpion 186 project boat with 1985 Mercruiser 140. And here my problem starts. The engine turns really really slowly. I'm pretty sure the boat wasn't in the water for few years. I changed the oil checked plugs there was no water in the cylinders. When I removed the plugs it turns kinda faster but still not fast enough. So I went went ahead and tried to do the compression test with all plugs out thinking that it will be okay but still when I put tester in first cylinder it was cranking so slow and hard. So the test failed. I changed the old oil which was still clean to rotella t1 sae 30 and oil filter as well. Don't know if that's the starter or what. I used my chevy truck battery that has 350 engine. Please help me as I'm getting more confused, also the cables from positive and negative are getting so hot & starter solenoid too. I really appreciate your help guys. I didn't try to start it by key I disconnected the round connector because the cables to dash are mess. So I shorted pin 5 & 6 together then touching pin 7 to 6.