Low range bog in 30/40hp mercury

[tyst67]

The motor is a 2003 30/40hp mercury! When I pull out hard from a dead stop my motor will bog right down and shut off! If I feather the throttle it won't shut off! Once I pull out, my motor works beautiful through mid range and wide open! I have a set of boyseen reeds installed as well! Anybody know what might be causing this!! Thank you!-

[omcstratos]

Well there could be a few different reasons.

1. Dirty carbs causing it to run lean
2. Float is stuck open, flooding out
3. If you have bigger carbs on it, you may want to play around on the jet size

Check your spark plugs, they can tell you a lot!

[tyst67]

Thanks!! I checked my plugs and they are black with a little light brown showing through! Like marble lol I think I'm running too rich but I didn't know it would cause this bog! Do you know of any performance plugs I can buy?

[tyst67]

Thanks!! I checked my plugs and they are black with a little light brown showing through! Like marble lol I think I'm running too rich but I didn't know it would cause this bog! Do you know of any performance plugs I can buy?

[omcstratos]

If you are going to check your plugs, you have to run it at the rpm's it is bogging at for maybe a minute. Then without going faster or slower shut off the motor and pull the plugs, they should be different than light brown if you bog down. Or possibly be wet with gas.

That being said, If you are running rich, plugs aren't going to solve the problem. They are only an indicator of your air fuel mixture.
Is your motor completely stock? Tell me what you can about it.

[tyst67]

Thanks! The motor is not stock! I bought the motor and all the mods were already done but I'm not a 100% what they all are! The exhaust is drilled down on the leg, boyseen reeds, intake is ported, pistons are supposedly fluted??? But I never saw them! The timing is advanced 8 degrees from stock, the guy that had the motor before me is good around outboards but the work on the motor was done by the guy that he bought the motor from! The motor works awesome through mid range and wot but I'd just like to figure out the hole shot!

[zul8tr]

What pitch and diameter prop are you using? What rpm at top speed? Do you know the gear ratio of the lower unit?

[tyst67]

10 3/8 18 pitch mercury chopper 2 , almost 6700 2:1 gear

[fs5]

has the motor been ported mate.

[tyst67]

The guy that had the motor before me opened up the intake manifold but I dont think there is any internal porting!maybe the motor would work better if I put a stock intake manifold back on !

[hydroplay]

Bogging when the throttle is advanced is a symptom of being too lean. That could be caused by the card itself being lean on the low speed or it could be because an altered intake lets the fuel falls out of the mixture because speed is too slow in a ported area. My choice would be to put a stock intake back on and see. If there's no bog the carb is ok. But if it still bogs, you gotta richen up the idle circuit. That's assuming all the rest of the stuff like float level is ok. Newer motors are set very lean on idle to prevent smoking and emissions- good for the EPA but not necessarily the operator.