what sensor sit in the middle of the intake manifold,,,has an electrical connection on top of it,,,cant find it in the manuals

Most likely IAT, which is Intake Air Temp sensor. However, it could also be your MAP (manifold absolute pressure) sensor. If the sensor is small it is most likely the IAT, if is is a little larger and has a small plastic box on it is it is the MAP.

Go here http://www.mercruiserparts.com/selec...oc_nbr=525+EFI, pic the serial number range that matches your engine. They have exploded views.

Wait....are you talking about Raylar 525's or merc racing 525EFI? ? I noticed you have raylars listed in your signature, totally different engine. The raylar is based of the merc 496 which would be this http://www.mercruiserparts.com/selec...EO%2E+Model%29

no its not a raylar engine,,,,stock 525,,,its not the iat,or the map,,,,i think its a fuel pressure sensor,,,,its sits in the middle of the intake,,,under the plentum,,,maybe its the fuel rail its sitting in,,,,anyway is the fuel pressure sensor near that area

If it's a four pronged, long, oval plug on the port side of a 525 you might be looking at the diagnostic port.

no its not the diagnostic port,,,its in the valley of the intake,,right in the center

Are you talking about number 13 ?

http://www.mercruiserparts.com/Show_...+And+Injectors

If not, a photo may help.

sure your not talking about the PCV?

yes it looks like #13,,,,but wouldn,t it be threaded into the fuel rail,,,this one looks like its threaded into the intake vally???

Yes, it is part number 13 and it is the fuel pressure sensor.

Best Regards,
Ray @ Raylar