Mercruiser 3.0 oil gauge problem

[trooper1954]

Have a 1989 mercruiser 3.0. When running at low rpm and speed the oil pressure gauge reads just under 30, but when I increase speed it drops to zero. Anyone help with troubleshooting this? What should normal oil pressure read at say 3000 rpms?
Thanks

 

[Scott Danforth]

Install a mechanical gauge and verify oil pressure. You could have a bad sender or a serious problem

 

[trooper1954]

Thx Scott... I'm not very mechanical but would like to try and fix this myself...can you tell me what I'm looking for in the engine compartment to attach a mechanical oil pressure gauge to....and is there a specific gauge I should get for this application?
The motor is a 1990 vintage, and it wouldn't surprise me if both the gauge and the sending unit are that old too.
Thanks for your help

 

[nola mike]

You can buy any mech gauge for $10-20. Not familiar with the specifics on the 3.0, but in general you can just unscrew your sender and replace it with the mechanical. 1/8" NPT threads.

 

[trooper1954]

Thx nola mike,
I*m guessing I'll need a 1/8th extension on the oil gauge to be able to see it?
Thx

 

[nola mike]

Depends on your setup, but possibly. You could get fancy and get a tee fitting and hook both gauges up.