Identitfy my 2 Mariner 175 Magnum EFI without serial number tag on transom mount !!

I just bought a1991 VIP 25ft walk around boat project. It came with 2 Mariner 175s and the cowls say MARINER MAGNUM EFI. However the i.d. tags are painted over. Is there anywhere else on the motor that a serial number can be found. I remember way back when on some motor I had we found the serial number on a block expansion plug, I think. There just has to be another i.d. point for an engine other than a exterior sticker. I hope ;-(

According to the service manual "the engine serial number is located on the top of the engine block" (no further specifics) as well as the plate.

I don't generally work on motors in this horse class and have never looked - perhaps someone familiar can narrow it down a bit...

Ok thanks graham. I will look for it this morning. If anyone else has a "mariner magnum efi 175" and can see their serial number elsewhere from the normal sticker on transom mount, please let me know specifically where and what to look for. Thanks to all.
Warren

Measure the cylinder bore to see if a 2.4 or 2.5, also look at VST tank,is electric fuel pump internal or exterinal mounted, does it have dual or single rectifier/regulators? Also look on flange of block behind throttle arm as build date is stamped in it...

Ok I found the quarter size silver expansion plug on near the top of the block and identified these two as 1989 v6 150hp carb motors. Yet, they have "MARINER MAGNUM EFI" on both the cowlings. I was told they were 175 hp and I assumed they were EFI until I opened them up and saw no control or fuel modules. Someone added the Mariner Magnum EFI cowlings on both of these. I bought this project 25ft boat, 2 motors 25" with stainless props and 10,000 lb heavy galvanized trailer at a price below what just the trailer is currently worth. So if these rough looking 150's with pretty cowlings are not worth time and money to fool with, I will just part them out and re-power with later 150 to 225 v6. Anybody out there got a pair of 2cycles injected Mariner or Mercs?