Bogging issue

[miscelaineous]

I have a 1992 40hp Johnson model # vj40tlenj (if needed), that will bog down from time to time. It will not do it all the time. Most time when I first crank it, it will run fine, with no problems. Sometimes I can take it out several days in a row and have no bogging issues,stopping and fishing, stopping and fishing, all day. Then there are days when it will do fine for several stops and then all of a sudden it will start to bog when I excelarate to fish somewhere else. I will either use the neutral lever to rev engine and it will clear itself out and will go fine and sometimes it won’t. If it won’t I will turn it off and fish a little bit longer and crank it again and it will do fine. Sometimes it will excelarate fine and plain off for a distance then bog down to slow speed. Changed fuel pump, fuel filter, change fuel line (tank to engine), and fuel connectors on hose, gas tank, (6 gallon). Helpful suggestions or questions to help understand my issue are welcome. First time user, have read many helpful threads to help in other situations. Thanks in advance

 

[gm280]

Interesting... Are you absolutely sure your gas tank is venting properly? Sounds like it could be starving for fuel during those bog times. And if the vent is not perfectly clear, air can't get in the tank as the gas comes out. Also, how many times have you filled up that tank? If you are getting questionable fuel (could have water in it from the station) it will do that bogging too. Just something to check...

 

[Shawnfish80]

Remove and disassemble your carbs and soak them in acetone,carb cleaner etc...(wichever cleaner you prefer). Could have something floating around in one of your carbs and clogging one of the orfices occasionally causing it to bog. Like said above it could also be a issue with your tank but from what ive seen over the years more often its the carbs or something else fuel related and you have already replaced everything between the tank and your carbs..

 

[Crosbyman]

when it bogs down have you tried testing /pumping the bulb

if it wakes up you probably have some fuel restriction see above " if the vent is not perfectly clear, air can't get in the tank as the gas comes out"

at least that would eliminate electrical issues

 

[miscelaineous]

WOW, Thanks for the quick responses. I have at times loosened the cap all the way when it bogs to make sure it’s vented and not restricting fuel, also I rotate tank usage (have 2, 6gallon tanks) after each outing putting fresh gas (non ethanol) and oil in tank used for that day with STABL marine gas treatment. I have ordered carb kits for the carbs which will be the next thing I do,(never removes carbs before, hope it’s not to hard) and have only replaced the fuel line tank to engine connect, not engine to carbs and prime solenoid. Have tried pumping bulb during bogging but to no avail. FYI.( When I first bought this boat back in 2018, had that bogging problem you are speaking of and when I pumped the bulb she would excelarate fine. Fuel pump changed, problem solved, but not this time). That was a constant excelarate bogging, this is a once in a while, ever so often, sometimes it does sometimes it don’t bog.

 

[gm280]

You probably already have done this too, but have you changed the fuel lines from the fuel pump to the carb(s)? And have you verified the fuel flow out of the pump lately? Just more ideas...

 

[Crosbyman]

using a good oil-gas mix ? water discharge ok ? not overheating ??

 

[miscelaineous]

Have checked but, not changed hoses from fuel pump to carbs. Will verify fuel flow before removing carbs. I use 2.6 oz per gallon oil mix, Johnson/evenrude premium 2stroke oil, 89 and 93 octane non ethanol gas. Had overheating issues last year, changed water pump issue solved. Water discharge great now.

 

[miscelaineous]

Cleaned carbs today, new parts, etc, haven’t river tested yet but sound good on land. Has always started find in cold weather but took several times to stay running. Today when I replaced carbs back on engine after cleaning stated first time in IDLE. Never did that before. Good so far on land. We shall see later on water. Question. Does any one know want the float specs are. ( distance from carb to where float drops ). And low speed adjustment screw on both carbs? Right now they are set at 2 1/4 turns from seated position.

 

[juno pierrat]

have manuals for 84' 70hp, 87' 48hp, and 90" 40hp all say 1 1/8 to 1 5/8 on float drop.

 

[miscelaineous]

Thanks. What will happen if drop is at say, between 3/4 to 1in. ( 22mm ). Really don’t want to take carbs back apart again, but I will if this is going to be a problem. What should I expect from engine at this drop? Any damage or running problems?

 

[juno pierrat]

Have the float level been set,set without gauge to level with carb body, below is from the 90" 40hp manual

8. Check for correct positioning of float level. Float level controls
the height of fuel in the float chamber and is very critical with
regard to carburetor calibration and function.
• Turn carburetor body upside down and hold so gasket
surface is horizontal. The weight of the float will close
the float valve needle. Rest OMC Float Gauge
PIN 324891 on gasket surface, and slide gauge up next
to float. Top of float should be between notches ® on
float gauge. Be certain gauge is not holding down the
float.
• If float level is not between the notches of gauge, lightly
bend metal float arm to adjust level. Be careful not to
force float needle valve into seat.
9. Check for correct float drop dimension. This dimension affects
the full opening of the inlet needle and is critical to correct
operation of the carburetor. With carburetor body in normal
running position, the float must drop open to dimension shown.
To adjust, bend tab on float arm where tab contacts float seat.

 

[Faztbullet]

Check to see if both cylinders have spark when it boggs...could be a pack failing and revving it up makes missing cylinder kick back in...

 

[miscelaineous]

Well, after cleaning carbs bogging issues seems to be gone. Went out fishing today and NO MORE bogging! Engine seems to hesitate a little when I give it the initial throttle but then excelarates fine. What can I do to help with the initial hesitation? Also notice that ONE of the 2 spark plug wires is sparking around the boot. Going to replace plugs and both wires but having a little trouble locating the proper plug wires. What is the gap for this engine? Thank for everyone’s help

 

[juno pierrat]

plug champion QL78YC @ .30. time for the old carb sync-n-link and insure spark advance lever under flywheel moves freely