Oil Pressure Gauge?

[CV-23]

Changed the 454 motor in my 270DA after freeze damage. Started fine but the oil pressure gauge is pegged at 80 lbs. It did it as soon as I turned on the key and while running. Engine running fine but did the sending unit die? Water temp and alternator guages fine also. Same year motor and the electrical plug between boat and motor were the same. Motor may be an '89 and mine is a '90. Any ideas? Thanks, Mike.

 

[bahamabreisus]

Check wire to oil sending unit, maybe it got crushed during installation. Could just be bad sensor.

 

[Steve Craig]

Still have the old sending unit or is it the one on your new motor ?
I've seen the sending unit ranges change over the years with GM products.
0-60 PSI, 0-80 PSI & anywhere between.
Full scale may indicate a couple things or more.
1 - incorrect range on the sending unit
2 - wiring gone to ground
3 - sure the sending unit is a sending unit & not a switch for lamp indication ?

 

[Mike Blake]

Make sure all your grounds are OK. Then beg borrow or steal an manual oil gauge just to check the real pressure. That way you will know what your engine is putting out.

 

[CV-23]

I still have my old engine for spare parts and the sending unit in hand. I unhooked the wire on the sending unit and the gauge is still pegged while running. My mechanic recommended that first. I also noticed another smaller sending unit, next to the larger one, going to my coil. Is that to cut the ignition if I lose oil pressure? Did not unhook that yet! Pretty cramped down there! I do have a mechanical gauge to check pressure worst case scenario! The wiring harness, engine side, is not exactly identical to my boat side harness......it's missing the trim gauge wires also. The pins all lined up but missing those trim wires on the engine side. May have to splice those in.....if I can find them! Did not want to swap engine side harness off the old motor but is there if I need to!

 

[Mike Blake]

Maybe try swapping the senders and see where you are .

 

[Bt Doctur]

What color was the wire you removed , a solid light blue?

 

[CV-23]

What color was the wire you removed , a solid light blue?

Yep.....off the sending unit. Nothing changed?

 

[CV-23]

Changed the sending unit....problem solved! 50-60 psi constant.

 

[bahamabreisus]

Yeah !!!

 

[CV-23]

New frustration! Engine temp cycling from 145 to 190. Impeller is new but thermostat may be going bad. Exhaust manifolds new also. Engine runs great but changing the whole housing tomorrow.....using my old one. Thermostat was new two years ago on my old motor. Hope my oil/PS cooler is not clogged.....still have the old one! Plenty of spare parts!

 

[SCORPIO]

You could unhook the cooler and back flush it with a hose to dislodge any debris. A new T-stat is cheap so while the housing is off, try a new one. Make sure the water pick up isn't obstructed by growth or foreign objects like weeds or plastic bags.

 

[CV-23]

Temp problem solved! The thermostat in the engine was a 160F and the bar holding the little plastic balls was shot. One ball could not seal due to corrosion. I swapped the housing off my old motor....it's a 140F thermostat and the balls and thermostat was replaced by me a few years ago. The two mating surfaces on the intake and housing were a bit damaged so I used a Mr Gasket reusable rubber gasket ($18) unit which worked perfect! I had two water leaks on the factory surfaces both front and back. This rubber gasket worked perfect! I also cleaned the sending units off.....some corrosion. I'm now rock solid at 145F and ready to boat with the motor update. Still need to splice in my trim gauge to the harness but I'm good for now. My gear drive bottle reservoir is not connected yet either. Any idea what color those wires are?