idle problem and oil pressure-gctid803837

[rivahlife]

Took a 1990 capri 18 ft with a 3.0 mercruiser out this weekend to try out before buying. I work with the current owner and he just got it back from the shop to have everything checked out. Machanic said everything works fine but when I had it out, the oil pressure was staying at 20. At one point it went up to 40 but didn't stay there long. This this normal for the 3.0? As long as he has had it, it's never wanted to idle without dieing. Can I adjust the carb to idle higher to fix that problem?

[Pcpete]

Welcome! Two things going there. What oil is in the engine. Others are going to scoff, but my experience is I get better continual pressure, especially when slowing to an idle after a long run, when I use the Mercruiser or Quicksilver brand 25w-40. At the same time you may be dealing with a sticky gauge or sending unit. Something else to check.

As to the idle, if it dies when shifting; 1) he's shifting too slow, snap that thing into and out of gear, there's a shift interruptor mounted to the engine that kills the engine for a microsecond to allow the shift dogs to engage or disengage. 2) the idle mix screws may need to be adjusted, but the mechanic that just pronounced everything's goo to go should have caught that.

[RobMick]

My oil pressure gauge at sea trial was fine. When I brought boat home and ran it for first time, it bounced about as yours seems to be doing. Ultimately, I was an oil pressure sending unit that was bad. I guess a simple fix. The type of oil I doubt would have anything to with the pressure of the system unless a different weight oil is being used from the recommended type. By law, a manufacturer cannot make you use their oil...if it's the same weight, then the the boat's performance should be the same.

[Pcpete]

RobMick, please note t was referring to my personal experience. In a previous set of engines I tried several brands, weights and blends to prevent the warning system from going off due to low pressure after a long run. When I tried the brand name stuff the oil cooed faster and I stopped having low pressure issues. In no case did I attempt to infer, or would I ever, that the use of manufacturers brand oil was required.

[builderdude]

"rivahlife" post=803837 wrote:
Took a 1990 capri 18 ft with a 3.0 mercruiser out this weekend to try out before buying. I work with the current owner and he just got it back from the shop to have everything checked out. Machanic said everything works fine but when I had it out, the oil pressure was staying at 20. At one point it went up to 40 but didn't stay there long. This this normal for the 3.0? As long as he has had it, it's never wanted to idle without dieing. Can I adjust the carb to idle higher to fix that problem?

IMO it's probably the sender acting up or the gauge or a loose/corroded connection.

[RobMick]

"Pcpete" post=803882 wrote:
RobMick, please note t was referring to my personal experience. In a previous set of engines I tried several brands, weights and blends to prevent the warning system from going off due to low pressure after a long run. When I tried the brand name stuff the oil cooed faster and I stopped having low pressure issues. In no case did I attempt to infer, or would I ever, that the use of manufacturers brand oil was required.

No problem Pete.....but I will say concerning oil and lubrication you will always pretty much get what you pay for! I am in the chemical industry and we manufacture lubricants in our line and I will NEVER forget what a customer told me once, now this guy is a "hands-on" still turning wrenches guy with 30 years of experience.....he said " now matter how much it costs, lubricants are ALWAYS gonna be cheaper than steel!" when I thought about that he is so right on it's not even funny. People will buy the cheapest tube of grease they can find then get po'd when there is a failure...

In your example, I would think that tthat he same weight oil would not send a low or false pressure reading...

[Chief_Alen]

Should idle in the water on a warm engine around 600-650 the less the better.

Don't want to idle " good ".

Low compression in one or more cylinders ?

Idle circuit in the carb clogged up ?

Temp this engine is running at ?

Choke opening all the way ?

Moisture in the dist. cap.

Run this engine in pitch black condition Zero light capiche ?

See if there are sparks all over the place.

1990 Bayliner ... leaky fuel tank .... water in the fuel maybe ?

[rivahlife]

Haven't had a chance to put it on the water since that first time but I did put the muffs on today. At idle in and out of gear it was idling at 300 rpm. Shouldn't it be higher out of the water? Note I did fill the tank up and added royal purple's additive and ran much better this time.

[builderdude]

"rivahlife" post=809234 wrote:
Haven't had a chance to put it on the water since that first time but I did put the muffs on today. At idle in and out of gear it was idling at 300 rpm. Shouldn't it be higher out of the water? Note I did fill the tank up and added royal purple's additive and ran much better this time.

Hard to belive it stays running at 300 rpm, sounds like a carburetor rebuild is in your future. Many times a carburetor can become "gummed" up with bad gas, deteriorating fuel lines, sediment in the fuel tank etc.

[Chief_Alen]

HA you believe the tach ?

Maybe he missed typed ?

For once i would like to know if he is boating at 9,000 feet.