Quote Originally Posted by lively View Post
what the ? i got a new oil sender for the 351 and before it was showing 0 -10 and i picked a new one up for a 86 f150 w/ 5.8Lfrom auto zone and the thing reads 80 psi ! and never moves .. i did notice when i removed the old one it had a reducer
from the pressure stem to the old sending unit , new one is like 1/2" NPT and the reducer was like 3/8" npt ... is there a special kind or something for boats ? new one on me
Not so much a difference between auto and marine but I believe some gauges use different range of ohms. You have to match the ohm range of the sending unit to the ohm range of the gauge.

Your gauge might operate in a range of 20-30 ohms and the sender you bought might be 40 ohms at idle.

Just a guess though. . .