50hp mercury runs great at idle. not in gear though

Im new to boats. Bought a 73 ebko fishing boat. Has a rebuilt 50hp on it. Starts easily and idles great. When put in gear it doesn't stall but bogs now and goes like 10 mph. I took the boat back home and noticed that the connecter on the engine for the fuel line there was a needle like thing hanging out. Im real confused. Don't have a clue about boats.

1965 500 50hp mercury runs great at idle. not in gear though

1965 500 50hp mercury runs great at idle. not in gear though

Bump. Replaced gas line insert on engine. Still does the same thing. I feel like im doing something wrong here. Oh btw its a 1965 mercury 50hp engine. 500 series. Please help thanks

Re: 1965 500 50hp mercury runs great at idle. not in gear though

Re: 1965 500 50hp mercury runs great at idle. not in gear though

Bog sounds like carb or a dead cylinder, you can have a dead cylinder for a lot of reasons,they're not all bad. I have a '77 500 Merc and I have been all thru it this year, carbs, fuel pumps, fuel line, 1 coil, new wires, new lower unit, and new plugs.

How many cylinders is your 500? I had a bog and I found that #2 wasn't firing. You can easily meter the plug wire to ground (while it's disconnected), you should get about 1050 ohms. Meter the primary on the coil to ground too, all coils should be the same. Make sure your are firing all cylinders. Remove the carb bowls and make sure there is fuel in them, I had a stuck needle and one carb went dry, this thing will run on 1 carb... just not well..LOL.

Re: 1965 500 50hp mercury runs great at idle. not in gear though

Re: 1965 500 50hp mercury runs great at idle. not in gear though

Well I checked to see if all my spark plugs were firing and the number four cylinder is not firing. What do I do from there

Re: 50hp mercury runs great at idle. not in gear though

Any advice?