My buddy next door has a 1967 big twin 40 hp outboard. When he bought the boat the guy said it ran its just old. He was able to get it to turn over but never fired up. He said he had sprayed carb cleaner in what he thought was the front of the carb or the air intake where the choke is. He said that is when he noticed it not turning over anymore. On my motorcycle and four wheeler i Have to drain the carbs everytime i let it sit for a long time. I have basic knowledge of my bike but minimal to nothing about boat motors. I checked his battery and it seems to have juice and when he turns the key the motor knocks one time and tries to turn over but doesnt. It has a pull start put it seems impossible to pull and have anything turn. Im not sure where to start other than making sure its getting power. I have it on a trickle charger for him and were gunna try in another day or so to rule out if its the battery or not. I feel like there is spark because the motor does something. but again i have no idea. he said he replaced spark plugs and bought a new battery and thats all that he tried. I hooked the battery up to his car battery with jumper cables and then tried to start the motor but again the same knock and tries to turn but wont keep turning over. Im guessing the solenoid or whatever it is, is the knock when it initiates the gear and then goes back down please help