Mercury 1977 115hp 1150

[brendan96]

I have an old mercury 1977 115hp outboard motor when I run it on the hose it's perfect but as soon as it's on the lake and has pressure it looses power, I can get up to speed for maybe 30 seconds but then will loose power and go back to idle or cut out then a minute later can get back up to full speed and then loose power again and so on. I have cleaned out the fuel tank, new primer bulb, rebuilt the fuel pump and carburetors and put new fuel lines in. But am running out of ideas, any help would be great.

 

[racerone]

It is NOT perfect on a hose.-------It only sounds good as it does not need to do any work.-----What condition is the wiring in ?----Any crumbling of insulation ?----Report the numbers of a compression test.-----Spark on all six leads ?