Nissan 18 HP 4 Stroke - dies under load

I have a Nissan 18 HP. It dies under load.


History
About 5 years ago boat flipped in a storm - freshwater - and the motor was submerged for a couple of hours. It was immediately brought to my mechanic who did what needed to be done to prevent issues.


When I got the motor back it dies under load. Idles fine and runs fine at super low speed, I start to open up the throttle it dies in about 50 feet.


Brought back to the mechanic - he tried everything he can think of - fuel pump, thermostat, nothing obviously wrong. It has sat his shop, unable to figure out.


I grabbed it back and removed carb - did complete and full cleaning and soaking. New plugs, new gas. Fires up. Runs great on muffs, neutral, and in gear no issues no signs of issues. Put on a 16-foot boat, started right up, and dies as soon as I open up throttle, then hard to restart.


Even though this 10 or 12 years old, it has very little hours on it and looks like new. I am at a loss at what to do. I can do simple mechanical things.


If you have tips or suggestions please let me know. Thanks.

We need your actual model.
Sounds lean.
Some 18s have a passage in the bottom of the carb bowl that feeds the acceletator pump. If that is clogged, it could cause your symptoms.

pvanv said:

We need your actual model.
Sounds lean.
Some 18s have a passage in the bottom of the carb bowl that feeds the acceletator pump. If that is clogged, it could cause your symptoms.

Click to expand...

It is a 2006 nsf18b2

Check that passage.