Hey guys I am new to outboards on boats but not new to boating. I have a 1980 witchcraft with a 115 mercury on it that seems to idle rough. The owner said he had it serviced every year and the water pump replaced also every year. He said this year since he didn't use it much last year he didn't take it in for service and only changed the spark plugs on it. Now I haven't seen spark plugs like these before since I mostly work on car motors or inboard motors. The are completely flat 
I am not sure if he got the right ones or not but he said that it ran great when he took it out last month. He started it up for me and showed me it went into the gears and reved it up but of course that's just on the hose.
So I started it at home and the motor shakes pretty good but sounds really strong so I am not sure if it is just normal of this motor or not. I am thinking of rebuilding the carbs on it and setting them to factory specs just to make sure they are in good working order. So my question is that is this normal for this motor to shake at a idle or not?
My next question is prop sizing for this motor. The owner said he had a 19p on it until he tagged a rock the last outing so his buddy gave him a 17p to throw on it but he never ran it with this prop. So I am wondering should I stay with a 17p or go back to a 19p SS? I am also wondering if I should go 4 blade or 3 blade. I will be mostly hauling the family around in it and sometimes tubing with it.
Any advice would be great for this motor! I am also going to get the service manual so I know what the specs are on the carbs and how to change the water pump also
Thanks!
I am not sure if he got the right ones or not but he said that it ran great when he took it out last month. He started it up for me and showed me it went into the gears and reved it up but of course that's just on the hose. So I started it at home and the motor shakes pretty good but sounds really strong so I am not sure if it is just normal of this motor or not. I am thinking of rebuilding the carbs on it and setting them to factory specs just to make sure they are in good working order. So my question is that is this normal for this motor to shake at a idle or not?
My next question is prop sizing for this motor. The owner said he had a 19p on it until he tagged a rock the last outing so his buddy gave him a 17p to throw on it but he never ran it with this prop. So I am wondering should I stay with a 17p or go back to a 19p SS? I am also wondering if I should go 4 blade or 3 blade. I will be mostly hauling the family around in it and sometimes tubing with it.
Any advice would be great for this motor! I am also going to get the service manual so I know what the specs are on the carbs and how to change the water pump also
Thanks!