Mid 80's Nissan 18hp getting too much fuel

[JMichael]

A buddy of mine has an 18hp Nissan that we've determined is getting too much fuel. I'm pretty sure the issue is too much fuel because I pinched the fuel line with a pair of pliars and by disconnected the fuel line from the motor while running. When it gets down to the last few seconds worth of fuel, it opens up and screams down the river like it should until it runs the carb completely dry, which isn't more than a few seconds. On the occasions that I was able to hold just the right amount of pressure on the pliars pinching the line, it would continue to run normal for extended periods.

Here's the limited info I have on the motor so far. The carb has supposedly just been replaced by the previous owner (no info on why it was replaced). The motor ran normal for my buddy for 1 whole day on the river the day before this problem started. The motor will start and idle like a brand new motor.

I feel pretty sure it's a carb issue and I told my buddy to pull the boat up to his shop so we can have a look at it. I'm just wondering if this is something someone knows of or that they've seen with a Nissan/Tohatsu before. I've worked on several motors that didn't get enough fuel but this is a first for one getting too much. I don't think it's a float height issue or it wouldn't start and idle so well and I've tried adjusting the mixture to no avail. So, any ideas out there as to what might be the cause?

 

[Whoopbass]

I would run the numbers on the carb and make sure it was replaced with the right carb since the jets could be wrong.
Remove the plugs after running the motor at wot and check and see if they're too wet.
Does this outboard have a regular choke or does it have a fuel primer system like some OMC motors have?

 

[JMichael]

It's got the old style butterfly choke system. I considered the jets as a possibility and plan on comparing the jets between the new and old carb (he got the old carb with the motor), but since he say's it ran great all day on that first day he had it, I have my doubts that it's the jets.