Logo
FULL SITE MENU

1999 mercruiser 7.4 mpi low oi pressure after head removed

S

sammi

Regular Contributor
My buddy has a 1999 mercruiser 7.4 mpi in a 340 sea Ray. Re had the right side head removed because of a rusted in spark plug. Marine mechanic removed head drilled out spark plug replaced head now he has 20 lbs pressure at start up that soon goes to 5 psi. We changed sender and guage individually and the problem stays on that side so it truly appears to be low. It was 40 psi known correct before head removal. What was not put back together right?
 
simply replacing a head would have nothing to do with the oil pressure. To eliminate all possabilities install a mechanical
gauge to test
 
that's because the distributor drives the pump....it its not installed correctly (fully seated), you won't have any oil pressure....
 
So it has like 5 psi and if you rev it it goes up a little to maybe 10 after engine is warm. If it comes up at all then its not a distributer issue? It was perfect 40 psi before. This just started after the head was put on. 200 hrs on motor.
 
Just throwing it out there but he put 5w40 rotella synthetic oil in last fall. Could that be an issue? The other engine has it though and it runs at 40 psi
 
Ayuh,.... Make sure the sender has a good solid Ground,.....

Something mighta been disturbed durin' the head work,....

No ground/ Bad ground, equals, No oil pressure on the gauge/ Bad oil pressure on the gauge,.....
 
Good point bondo. The ground basically is where it threads into the fitting right? So if I just scraped away the paint on the side and stuck a wire from the bare metal side to a manifold bolt that would work as a test right?
 
Back
Top