80 or 81 merc runs rough won't idle

Hi everyone i'm new to the site. I have a 1980 or 81 merc 115. Last time I took it out I left the dock and she was running good. made it about one mile and she started to lose power. I turned around to head back to the dock made it about 1/2 mile then she died.i could get the engine to start in neutral with full throttle ran rough felt like it was missing. as soon as I try to bring it down to an idle and get it into gear it dies. Used the kicker motor to get back home. I first checked spark good blue spark at every plug. Plug where fouled a bit so I replaced the. checked fuel line and filter. Filter was clean and line was ok. Compression was 130 give or take 2 pounds at each cylinder. Want to check for fuel pressure & volume but I don't know what it is suppost to be can any one help or have any other Ideas. Thanks

Re: 80 or 81 merc runs rough won't idle

if the motor starts now , it may have over heated, if you have not rebuild water.it need replaced one a year I have been told.

Re: 80 or 81 merc runs rough won't idle

At idle fuel pump pressure should be 3-4 psi. At wide open throttle 5-6 psi on inline 6 cylinders. C-91-30692 is the pressure gauge tool number that u hook into the gas line between fuel pump to carb. might be cheaper just to rebuild fuel pump then buying gauges, if u don't have a gauge u can disconnect the gas line at the bottom of fuel pump squeeze primer bulb or turn the motor over and check for good flow. Then un hook line at top of fuel pump to carbs and do the same. Hope this helps.

Re: 80 or 81 merc runs rough won't idle

Thanks for the replys. First things first. When I started to notice power loss I first thought it feels like it was over heating. I don't have a temp gauge so don't know what the temp was but the engine was peeing a good stream of water. Now thanks for the psi. Rating that you gave me now that I know I will check the volume and pressure this weekend and get back to you guys thanks agin