Logo
FULL SITE MENU

82 Merc 40hp WOT issues

C

cloudix

Member
"I have a 40hp merc serial # 5

"I have a 40hp merc serial # 5994510. The engine starts and runs perfect except when at WOT. It will run fine in WOT for about 2 min's or so then it wants to bog down and die (never does to with the throttle up to about 90% or so). If you pull the throttle back to idle when it does this it will spit and spudder then start idleing correct.

I bought this motor used, but the recitifier, switch box, both coils are new. the fuel pump and carb have been rebuilt. I tested the trigger and stator at the switch box (with the wires disconnected from the box) and here is the values i got there with my digtal meter.

trigger 890 ohms
stator bl/wh and grd = 225
bl/y and grd = 2420
bl/y and bl/w = 2644

I suspect this is a fuel problem, (like a small air leak from the fuel pump or after). I know 100% that the line up to the fuel pump is good and no leaks. I was thinking to replace the fuel pump diaphram, but im hopeing that someone else has some ideas."
 
"When it starts to sputter on

"When it starts to sputter on you, pump the fuel bulb - if that improves things, replace the diaphram - if it doesn't then whoever cleaned the carb probably missed a clog..."
 
"Sounds like its sucking air f

"Sounds like its sucking air from one of the fuel lines, tighten all clamps, even the one under the electrical harness at the fuel quick connect"
 
"ill give that a shot. I know

"ill give that a shot. I know that the fuel lines to the fuel pump are not leaking, cause i have seen the bulb sucked flat and was holding the vacume. From the fuel pump to the carb im not 100% sure. Ill let you know my results after this weekend."
 
"Yea, it did that when it was

"Yea, it did that when it was in storage and the vent was closed. I have the vent open only when im running the engine."
 
"Installed the Fuel pump rebui

"Installed the Fuel pump rebuild kit and The first time i ran it, it was fine for about 15 min. Then i cut the engine off and was fishing, the next time i ran it the problem was there. I pumped the bulb while it was running and having this problem and the issue goes away. What would you do next? I have a water seperating fuel filter (looks like a car's oil filter), its farily new. could this be causing the problem?"
 
"try a different tank or doubl

"try a different tank or double check all the hose clamps again. The fuel pump works off the compression cycles of the engine, check compression."
 
Back
Top