No, no weird mapper, just the $6100 issue I described above.
@davidstech: I now know how the game detects palettes --- by reading from $4119. On the VT03, $4119 returns $00 on NTSC and $18 on PAL consoles. On NTSC consoles, a game needs to compensate for the CGRAM DMA error if it uses DMA. Champion Boat on the other hand uses the 4-4-4 RGB palette if $4119 returns anything other than $18, and the old VT03 palette if $4119 returns $18. I don't think that's the way one is supposed to do it, but the lesson is: for this hardware, $4119 needs to return $00 and not NTSC/PAL like an original VT03.
It's still good that I made the modification yesterday. Basically, before I just had Nintendulator always return $18 so games would not try to compensate for the CGRAM DMA bug, because I did not want to emulate it. I had tried to emulate it, but ran into the problem that VT09 games assumed that the bug did not exist (because it may have been fixed by that time) and had no easy way to tell whether the bug should be emulated or not. I am now emulating it if a CGRAM DMA transfer starts at 3F01 and not emulating it if a CGRAM DMA transfer starts at 3F00, and I accurately make $4119 return the TV system except for mapper 296, under which $4119 always returns $00. That should work with any game in any TV mode setting.
Here is my extract of DGUN-2573. Only includes games accessible from the menu. Download
today's updated Nintendulator build for the aforementioned palette correction.
Edit: Please redownload the multicart extracts; made a correction fixing uninitialized RAM in the PCM music-using games.