Running Temp and Oil Pressure on a 454?

[Wills.WindowsAndWheels]

Hey i was just wondering if anyone knows what the standard cruising temperature on a Merc. 454 is? I get a little uneasy when i see it get up to the 3/4 mark.

Also i notice the oil pressure drops quite a bit (under 1/4) after running it and the oil gets quite hot. Is this normal or should it be staying up near the 1/2 mark?

 

[04fxdwgi]

Re: Running Temp and Oil Pressure on a 454?

Hey i was just wondering if anyone knows what the standard cruising temperature on a Merc. 454 is? I get a little uneasy when i see it get up to the 3/4 mark.

Also i notice the oil pressure drops quite a bit (under 1/4) after running it and the oil gets quite hot. Is this normal or should it be staying up near the 1/2 mark?

There are alot of variables in your question. Hard to say when a gauge has no actual pressure / temp readings on it. Is 1/2 way on the pressure gauge 20 psi or 40 psi, or put a different way, is the oil pressure gauge a 0-60 or a 0-80 gauge? Same for the temp gauge. One way to be certain, is to connect a mechanical oil pressure gauge in there in tandem to compare readings and then you can make an informed conclusion of what is good and what isn't. On the temp, you can use a hand held thermal gun right were the sensor screws into engine and get a pretty good idea what's going on, temp wise.

All I can say is that my '92 454 Mercruiser sits right around 40-50 psi on the oil pressure cold and a solid 40 psi when hot (30-35 at hot idle) and temp stays right on 160 deg when at temp. But my gauges have actual indications on them, verified accurate by connecting mechanical gauges in tandem to test and to compare. Of course, that depends on year and model, as operating temps differ, especially on the carb version, vs: EFI version. You need the manual for your specific setup to know exactly what is supposed to be going on.

Merc says oil pressure can get down to 10 psi hot, but I would be quite anxious if I saw it that low.

 

[dollarten]

Re: Running Temp and Oil Pressure on a 454?

There are alot of variables in your question. Hard to say when a gauge has no actual pressure / temp readings on it. Is 1/2 way on the pressure gauge 20 psi or 40 psi, or put a different way, is the oil pressure gauge a 0-60 or a 0-80 gauge? Same for the temp gauge. One way to be certain, is to connect a mechanical oil pressure gauge in there in tandem to compare readings and then you can make an informed conclusion of what is good and what isn't. On the temp, you can use a hand held thermal gun right were the sensor screws into engine and get a pretty good idea what's going on, temp wise.

All I can say is that my '92 454 Mercruiser sits right around 40-50 psi on the oil pressure cold and a solid 40 psi when hot (30-35 at hot idle) and temp stays right on 160 deg when at temp. But my gauges have actual indications on them, verified accurate by connecting mechanical gauges in tandem to test and to compare. Of course, that depends on year and model, as operating temps differ, especially on the carb version, vs: EFI version. You need the manual for your specific setup to know exactly what is supposed to be going on.

Merc says oil pressure can get down to 10 psi hot, but I would be quite anxious if I saw it that low.

Merc is probably saying 10 pounds at idle when hot and should rise as engine RPM is increased . Those old type oil warning lights will not come on until oil pressure gets down to eight pounds

 

[04fxdwgi]

Re: Running Temp and Oil Pressure on a 454?

Meant to say at idle, but forgot it......

 

[cr2k]

Re: Running Temp and Oil Pressure on a 454?

10 psi oil at idle good. 35-40 at WOT is OK. Oil pressure will drop as oil warms up. What viscosity are you using? 30w is too low. Temp gauges on boats are notoriously inaccurate, but should be the same area every time.

 

[Wills.WindowsAndWheels]

Re: Running Temp and Oil Pressure on a 454?

10 psi oil at idle good. 35-40 at WOT is OK. Oil pressure will drop as oil warms up. What viscosity are you using? 30w is too low. Temp gauges on boats are notoriously inaccurate, but should be the same area every time.

Wow you really think 30w is too low? All the marines i spoke with advised 25w....the previous owner advised 5w! It does seem to be consistent but ran into some issues tonight.

See we JUST had the impeller and housing replaced...we let a mechanic buddy of ours do it since he said he's done boats before...but heres what happened...

The first time we took it out...after running it for about a mile or so we cut it to do some fishing...20 minutes later the BILGE kicks on and spits out water! So we lift the hatch and look in...we hear DRIPS of water...but see nothing bad running...so we head back to the dock....get 1/2 way there and end up having to tow someone in (a lady and her 2 kids) cause THEY stalled lol....but the temp held at dead center (175 i found out tonight) the full time.

We pull the plug after getting the boat out and water came pouring out, when before this work was done NOTHING would ever come out.
So we took the boat home, hooked up the hose and checked for leaks, but found nothing...so we changed the plug and checked our prop to make sure it was good and took it to the lake tonight...and thats when the fun started.

Started up and rose to 175 as usual. Started heading out real slow, about 1/2 miles from the dock and all the sudden the temp starting rising FAST. It went to 3/4 in just a few seconds (about 225) so we cut the motor. Checked for leaks again and saw nothing. I ended up having to swim and pull this big bit** in (24 ft 4 ton boat).

SOOO here is what we THINK happened....you know how the impeller has to be twisted counter-clockewise when put into the housing? Well we THINK the guy put it in backwards...and that when we went out the FIRST time, that it pushed whatever water was in the motor still out into the engine compartment...and then when we took it out tonight it was pulling in no water, thus overheating so quickly. Either that or he FLIPPED the 2 hoses that connect to the Sea Water Pump housing.

What are your thoughts on that?

 

[tpenfield]

Re: Running Temp and Oil Pressure on a 454?

temp should be 155 on a 454 - it uses a 143 thermostat. oil should be 10w - 40. Oil pressure should be 30 - 50 psi it will tend to drop more towards the 30 psi range once the engine gets hot.

Sea water pump has the outlet hose closest to the oil pan. The one further away is the inlet side from the transom.

 

[PuddleJumper]

Re: Running Temp and Oil Pressure on a 454?

Wow you really think 30w is too low? All the marines i spoke with advised 25w....the previous owner advised 5w! It does seem to be consistent but ran into some issues tonight.

See we JUST had the impeller and housing replaced...we let a mechanic buddy of ours do it since he said he's done boats before...but heres what happened...

The first time we took it out...after running it for about a mile or so we cut it to do some fishing...20 minutes later the BILGE kicks on and spits out water! So we lift the hatch and look in...we hear DRIPS of water...but see nothing bad running...so we head back to the dock....get 1/2 way there and end up having to tow someone in (a lady and her 2 kids) cause THEY stalled lol....but the temp held at dead center (175 i found out tonight) the full time.

We pull the plug after getting the boat out and water came pouring out, when before this work was done NOTHING would ever come out.
So we took the boat home, hooked up the hose and checked for leaks, but found nothing...so we changed the plug and checked our prop to make sure it was good and took it to the lake tonight...and thats when the fun started.

Started up and rose to 175 as usual. Started heading out real slow, about 1/2 miles from the dock and all the sudden the temp starting rising FAST. It went to 3/4 in just a few seconds (about 225) so we cut the motor. Checked for leaks again and saw nothing. I ended up having to swim and pull this big bit** in (24 ft 4 ton boat).

SOOO here is what we THINK happened....you know how the impeller has to be twisted counter-clockewise when put into the housing? Well we THINK the guy put it in backwards...and that when we went out the FIRST time, that it pushed whatever water was in the motor still out into the engine compartment...and then when we took it out tonight it was pulling in no water, thus overheating so quickly. Either that or he FLIPPED the 2 hoses that connect to the Sea Water Pump housing.

What are your thoughts on that?

If in and out hoses reversed you wouldn have made a mile without over heating.
your statement about water in bilge and a new pump and housing makes me think of loose or cracked hose, overtightened pump housing with leak or crack in new housing.
If old pump was chewed up r u sure he flushed out the old impeller pieces? Could cause obstruction.

 

[45Auto]

Re: Running Temp and Oil Pressure on a 454?

SOOO here is what we THINK happened....you know how the impeller has to be twisted counter-clockewise when put into the housing? Well we THINK the guy put it in backwards...and that when we went out the FIRST time, that it pushed whatever water was in the motor still out into the engine compartment

Exactly what orifice on the motor do you think it pushed this water through? Only hole in the motor that connects to the engine compartment is the carburator intake.

Why makes you think a reversed impellor could push the water anywhere a normal one couldn't?? It always spins and pumps in the same direction.

 

[Wills.WindowsAndWheels]

Re: Running Temp and Oil Pressure on a 454?

If in and out hoses reversed you wouldn have made a mile without over heating.
your statement about water in bilge and a new pump and housing makes me think of loose or cracked hose, overtightened pump housing with leak or crack in new housing.
If old pump was chewed up r u sure he flushed out the old impeller pieces? Could cause obstruction.

Ya thats what threw me off...the 1st time we made it out and back ok other than the water in the engine area...the second time however we DIDN'T make it a mile before we over heated. We plan to completely remove the impeller again, check the hoses/impeller/housing.

The old impeller was still in decent shape, but we've heard its a good idea to change it yearly so tahts why we did it. How would we go about flushing it out?

Exactly what orifice on the motor do you think it pushed this water through? Only hole in the motor that connects to the engine compartment is the carburator intake.

Why makes you think a reversed impellor could push the water anywhere a normal one couldn't?? It always spins and pumps in the same direction.

Well thats what i was trying to ask...if the 'fins' or 'blades' if you will - of the impeller are turned the OPPOSITE direction they are suppose to be,is it POSSIBLE that it could pump/push water into the engine area? That was something i was concerned with as a possibility...