87MagnumII

Got my new to me 350 MAG MPI in and running. It fires up and idles great, but it has a hesitation/bog when you lay the hammer down to get on plane. If you ease into it, it will go. It also has a surge in the middle rpm range occasionally. Runs fine on the big end, turns a 21 mirage to the rev limiter through a 1.50 drive. Should I be looking at TPS, fuel pump, etc? I haven’t had a chance to check anything yet, just looking for some help on the go to stuff on these engines. Here’s a few pics from today’s test ride.

Trash

Need more data.

What year motor and serial# (BUP style...inside joke).

Is the motor modified, crate motor or a take out?

What is the WOT rpm?

Has the ECM been tuned or tweaked?

An easy TPS check is to do a voltage sweep. KOEO (key on engine off) and read the TPS voltage from idle to WOT in a slow sweep. Should go from roughly zero to just shy of 5 volts without jumps or hang ups.

87MagnumII

serial is 0L316222 (I believe it’s a 1998 model)
I bought it used, it’s a take out from a boat that came off the trailer. It’s stock as far as I know but does appear to have maybe had a refresh because it’s got new looking oil pan gasket. WOT it’s turning 5000-5200 RPM. It runs strong on top end, getting there is the struggle

Trash

Start with the TPS voltage sweep. That is a relatively easy test. If that's normal we need to look at other stuff.