76 johnson doesnt like WOT!

earl202

Recruit
Joined
Sep 21, 2002
Messages
3
Please help!<br />I have recently bought a 76 15hp johnson, on a 14 ft starcraft alum and have had the following problems.<br />The first day I took the boat out fishing and ran about w/ no difficulties until later in the afternoon when I noted the fuel filter (glass, in line type) falling apart and decided to remove filter and when out and got another..<br />I after replacing the filter the engine was running very rough and WOT would only last a few moments before killing engine.<br />Okay... I rebuilt the carb, put on new fuel lines and pump. <br />Went out and found the engine ran terrible. Found top plug not working, and replaced.<br />Ran great after all this work. Ran WOT for 20min, no stall problems.<br />Next trip out, ran great and dies when wot for 10-30 seconds. check float level and passeges and fuel lines for leaks. Went back out and ran great, WOT stalling persisting . :( <br />At the end of my last test lake run the top plug began to fail again and had to come in on one plug.<br />By the way the engine runs great at wot if you pump bulb ocassionly on stall.<br />I feel i have two problems, fuel delivery and ignition or are they related.<br />ps. Sparks are good, failed plug is baked.<br /><br />Thanks for any insight...
 

thefishingfreak

Seaman Apprentice
Joined
May 12, 2002
Messages
46
Re: 76 johnson doesnt like WOT!

if you have portable fuel tanks make sure the vents are open or you will have a vaccume effect on the fuel
 

earl202

Recruit
Joined
Sep 21, 2002
Messages
3
Re: 76 johnson doesnt like WOT!

I do have the tank open. I have pressure tested the fuel lines and made sure no obstruction keep the fuel from having back presure.<br />.<br />Keep the suggestion coming. :confused:
 

Squeakit

Petty Officer 1st Class
Joined
Jul 1, 2002
Messages
216
Re: 76 johnson doesnt like WOT!

When you say the failed plug is baked, what does this mean? All carboned up or fried as in insufficient fuel getting to top cylinder. I would check the compression of both cylinders to see if there is a notable difference. I would also check the reed valves to see if the top reed is damaged or malfunctioning. If you are sure that there is no leakage anywhere from fuel tank to carb bowl there must be some reason for top cylinder quitting. If no leaks, reeds OK, carb clean with proper float level, compression OK then maybe the timing is off for the top cylinder - if your engine has points, one set might be way out of adjustment causing timing error. If all this checks out OK, I'd probably pull the head off and check the water passages (maybe your top cylinder is overheating) and replace the gasket. Just a few ideas. Good Luck!
 

earl202

Recruit
Joined
Sep 21, 2002
Messages
3
Re: 76 johnson doesnt like WOT!

Great suggestions. I will get back with my findings. When I say the top plug is baked, i mean that the plug no longer fires and must be burning out internally. The top plug will no longer fire . <br />If I replace the plug, as done once before the motor will run great and still have the fuel problem.<br />I will repost with my findings. :)
 
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