ok guys I have a 2000 70hp jhonson the original tach warning lights stopped working. The tachometer always read around 5800 wot with a 13x19 prop.So I ordered a new faria tachometer and it would read around 4800 wot. I thought maybe the new tachometer was bad so i sent it back to faria.They sent it back saying they recalibrated it. So I tried the 13x19 prop again it would still only read 4800. I changed the prop to a 13x17 and it reads the same 4800. So im kinda confused on what could be going on