Mercury 115 on Starcraft won't rev up when throttle lever is down

We just got a new (to us) Starcraft 1700 1995 Bowrider. We've taken it out 3 times, all went fine.
Today, it's Mercury 115 (1995) fired up very nicely, & when I put it into gear, it went forward. But when the lever was down for full throttle, the engine wouldn't rev up high but just continued slowly.
It will also not rev up much in neutral.
The previous owner said that the throttle cable was replaced 4 years ago.
Any ideas?

1, Verify the throttle is opening when it should.

2. If it is, try pumping the bulb and see if this makes any difference.

Jeff

The throttle opens, and the bulb made little difference, but I noticed that there was a silver connecting rod that wasn't attached (please forgive my ignorance of engines, the photo is the first link) so I clipped it back in where it seemed to go.

Photo 1

After I did that, the engine now does the opposite. It starts up running too fast and when I make any throttle adjustments in neutral, it suddenly roars. (I didn't try to engage the prop)
Here's what it looks like now:
Photo 2
Photo 3
I heard that these engines start off with 2 cylinders and kick into using 4 cylinders when the RPM gets higher. Could that be the problem?

Problem solved.
That silver connecting rod wasn't put back in correctly. It needed to be fit into the little hole, not clipped around it.
In addition to that, it appears that the rocker that it was pulling activated a button on the bottom that was a small fuel pump (part # 17703-C).
That button was worn and when we turned it around, it worked much better.
Thank you for your help.