1999 Mercury 40hp bogging under load.

1999 or 2000 merc 40 hp 2 cyl engine

Serial number 0g963884

Just bought a 99 fisher dominator with this engine on it.

Background.
Boat sat for a few years.
Boat would start but wouldn't run over an idle. Found cracked fuel line running to primer solenoid. Replaced line. And new gas. It would then Start/run and had a few good outings on the boat. Would rev 5200-5400 rpm. Start easy ran smooth etc.


Then one day put it in the water. It started great. Ran great at WOT for about 5 minutes. Then it bogged down and shut off. Started back but wouldn't rev over 2000 rpm under a load. Any more throttle and it would die out unless the throttle was cut back. Unless you Push the key in and it would pick up to 3000k sometimes 4000 rpm but only for a few seconds..

Here's what I've done so far.
Sea foam in the tank.
Pulled carb and somewhat cleaned with carb cleaner and reassembled. (I couldn't figure out how to get the float pin out)

Pulled fuel pump and disassembled. No rips or tears but one of the clear round prices did seem to have a crease in it making it hold open farther than the other.

Also pulled plug wires on it while it was running. (This part seemed odd to me)
Pulled one. Didn't make a difference. Pulled the other, it died. So I swapped the coils around. Tryed it again to see if the problem moved. Both of them made a difference this time. Started miss firing when pulling each off.

Took it out again. Ran great for about 20 minutes before doing the same. Now it Will let you throttle up to around 2200 rpm before it will bog down and try to die.


So what's the next step?
Redo it all? With new fuel pump kit and actually tear the carb all the way apart?

Or coil cutting out when it gets warm?
How can I test?

Replace entire fuel system from tank inlet to carb to prevent future problems. Pull carb. thoroughly clean and rebuild it. Make sure she's not running hot,overheating. Is your water pump impeller working ? boat sat a few years right.

Already started on that. Found a lot of old crunchy lines. Also already rebuilt the fuel pump and noticed the gasket behind it was tore. Also going to tear the carb back apart today and soak it.


any suggestions on how to get the float pin out? Other than hitting it with a punch and hammer?

also it's got a nice pee stream. And you can lay your hand on the engine after it's been running so it's not over heating.

that pin should just slide out,wd-40

Got it, think I might have found the problem. Round gasket in the middle was good but had pieces of an old gasket stuck to the carb body. They were flaking off, the carb was full of little black pieces. Cleaned it all up. Ran good, till I got a solid beep about 30 minutes into the trip.



I loaded the boat up and came home to find out when I cleaned the oil tank out, I must have broken the float somehow. The alarm turns off when you lift up on the float. I disconnected the wires until I can try to adjust it or fix it. May try it tomorow for a little longer to be sure.


anyone have any input on unhooking the float wires for a while? Are any other alarms hooked in sequence to that alarm?

why not convert to premixing fuel and eliminate oil tank, less$$$$

it may be the eventual outcome. I don't really trust the oil injection lol.

Is this how my fuel lines/oil injection should be routed, because mine has the oil being injected after the fuel pump? That's the way it was when I got it.

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