Mercury 50hp 2003, No acceleration without hitting choke button.

cturboaddict

Petty Officer 1st Class
Joined
Aug 29, 2010
Messages
224
Motor: 2003 Mercury 50hp 3cyl
Condition: Hardly used, low hours, garage kept

Issue:
Yesterday took out my buddies fishing boat after a year long sitting for it's first ride. Started fine, but had some trouble idling. Once out on the water, sounded a bit rough (sort of like it wasn't firing on all cyl or there was water in the fuel?) on idle and would not accelerate when advancing the throttle. It would actually bog a bit and would sit at around 2500 rpm with no acceleration.

Hit the choke button and let off, and the motor would accelerate. If I tapped the choke button at a consistent rate, the motor would then accelerate and get up on plane. Not to its fullest potential though.

We first assumed the gas may have gone bad, but he said that he treated it with Stabil last year upon putting her in the garage. When we got back in, we decided to take a closer look and drain the fuel. As soon as we took the cover off the boat, we noticed that the air box was completely loose, and that the it was basically hanging off.

We drained the fuel, and it looked good. But replaced it anyhow. We have not tested since putting the airbox back on...

But does anyone have any idea what this could be? Or where we should check before moving forward. Could the air box being off like that cause this? I'm assuming that the boat wasn't getting enough fuel, because it ran better when hitting the choke button dumping more fuel into the carbs. And possibly haveing the carbs partially blocked off by the loose air box?

Motor is barely used, and ran great last year when put up.......
 

enginepower

Petty Officer 1st Class
Joined
Jul 5, 2014
Messages
260
Airbox shouldn't really affect it that much. Sounds like you have a leaking carb gasket or you need to clean your carbs.
 

cturboaddict

Petty Officer 1st Class
Joined
Aug 29, 2010
Messages
224
Drained tank, new fuel, cleaned carbs out a bit with spray seafoam, put in new plugs. Won't idle on the muffs out of the water in N without a bit a gas. Haven't water tested yet, but that's next on the list before I go turning screws without direction.
 
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