[Reaper22]

Ok took boat out and was running great trimmed out prolly 57mph and all sudden loss power dropped to like 40mph and would not get above 30 rpm or so, Shut down to neutral and idled fine, Took off again and could not get over 50mph and then it jus bogged way down so I threw it in neutral and the oil horn went off cuz zero oil pressure, Temp in boat was normal, Shut down and opened hatch and seen oil down in hull so I checked oil and was bout a quart low (was full and clean before I went out) so I had a quart of 30wt oil in the boat and figured at this point oil is oil so I added it and started the engine and oil pressure was at 40psi at idle and could not see a leak, So I had a guy tow me close to the boat ramp and took boat home, At home I hooked water to the boat and run if for like half hour and could not find a leak, Boat is at a shop now and we looked at oil and it is still clean, Mechanic did not want to speculate on what went on but did say he wasen't real concerned bout internal damage because oil was good and clean and said if oil pressure would have went to zero at 50mph motor would be trash, but was concerned bout why it would have lost power and the oil pressure, So my question is does any one have any idy what could have been or what is goin on with issue would be greatly appreciated...... The owner before me said he had it out 4th July weekend with no problems...
1995 Mariah Shabah Z212
Mercruiser 350 Magnum Alpha1

[GaryDoug]

I believe your engine has the MPI engine with an ECM module? If that is true, the ECM will limit RPM
(by disabling half of the injectors) to about 2800 RPM if there is low engine oil pressure, low I/O fluid level, or high coolant temperature present. I think that is why you had the power loss. Your mechanic should have known that.

From the 96 service manual:
"If a switch (oil pressure sensor) changes state from its normal at rest position, that is normally open to closed, the ECM senses a change in voltage and responds by entering power reduction mode.
This engine protection feature allows the operator full engine power up to 2800 RPM, but disables half of the fuel injectors above 2800 RPM until the engine RPM drops to 1200 RPMS.
This feature allows the operator a comfortable maneuvering speed while removing the possibility of high RPM engine operation until the problem is corrected"

[TCJ95Z-235]

Don't have any insight for you on the power loss but as far as a possible oil leak source, if you have a remote oil filter check where the remote mounts to the engine block at the original oil filter location. I have a 7.4 in mine and started seeing small amounts of oil in the bilge and finally found this was the source of my leak. Could not turn a wrench on it so I had to buy a socket (I believe it was a 1 and 5/16")

[Reaper22]

Originally Posted by GaryDoug

I believe your engine has the MPI engine with an ECM module? If that is true, the ECM will limit RPM
(by disabling half of the injectors) to about 2800 RPM if there is low engine oil pressure, low I/O fluid level, or high coolant temperature present. I think that is why you had the power loss. Your mechanic should have known that.

From the 96 service manual:
"If a switch (oil pressure sensor) changes state from its normal at rest position, that is normally open to closed, the ECM senses a change in voltage and responds by entering power reduction mode.
This engine protection feature allows the operator full engine power up to 2800 RPM, but disables half of the fuel injectors above 2800 RPM until the engine RPM drops to 1200 RPMS.
This feature allows the operator a comfortable maneuvering speed while removing the possibility of high RPM engine operation until the problem is corrected"

Thanks for the quick reply bro, I do not have fuel injection, I have a 4 barrel carb on this engine, It is a 350 magnum so maybe it has a wired in safety of some sort... btw it has 512 hours on it..

[GaryDoug]

Ooops. I doubt that the ignition system has a safety feature for low oil pressure. But I do see in the 96 manual a wire going from the oil and temp switches to the distributor that says, "not connected". I wonder why it is there. Or perhaps it is used only on some installations. It is a tan/blue wire.

[Scottie1961]

Originally Posted by Reaper22

Mechanic did not want to speculate on what went on but did say he wasen't real concerned bout internal damage because oil was good and clean and said if oil pressure would have went to zero at 50mph motor would be trash, but was concerned bout why it would have lost power and the oil pressure
1995 Mariah Shabah Z212
Mercruiser 350 Magnum Alpha1

I have the same engine and I'm not aware of any ECM initiated limp mode. There's not really an ECU/ECM on these models. I would be most concerned about where the oil came from. There's only so many places that much oil could escape. Was there any oil on top of the engine or on the sides? There must be a leak that only shows up when engine is running above certain RPM's? If any ignition parts got oil on them that could explain power loss. You could have also lost advance from the ICM which would cause engine to lose all top end.

Before running the engine again, I would determine where the oil came from and do a compression check to ensure the motor is in good shape. The loss of power may or may not be directly related but an oil pressure issue is number one priority and must be identified and fixed prior to running the engine at speed.

[Reaper22]

Originally Posted by Scottie1961

I have the same engine and I'm not aware of any ECM initiated limp mode. There's not really an ECU/ECM on these models. I would be most concerned about where the oil came from. There's only so many places that much oil could escape. Was there any oil on top of the engine or on the sides? There must be a leak that only shows up when engine is running above certain RPM's? If any ignition parts got oil on them that could explain power loss. You could have also lost advance from the ICM which would cause engine to lose all top end.

Before running the engine again, I would determine where the oil came from and do a compression check to ensure the motor is in good shape. The loss of power may or may not be directly related but an oil pressure issue is number one priority and must be identified and fixed prior to running the engine at speed.

Thanks for yur info man, I had the engine running for about 40 minutes and with a good flashlight and could not find the leak, There was no sign of oil on top of the engine except splatter drops kinda like if you took a spray bottle a mist it all over, no puddles, I could see drips coming from different places but believe it was also due to splash, Looked dry under valve covers, intake, sides of oil pan.. Even looked like spray on top of breather cover.. The mechanic that has the boat is a very good boat mechanic, His dad has had the business for over 50 years and he has worked on boats since he was a kid so I trust he will find all that is wrong I am just looking for some answers right now because he is a week out before he gets to it, I hope and pray it is not a serious and costly fix, BTW to be honest about the oil pressure not real sure if engine hadn't died and the low oil horn goin off and when I restarted it I may have not gave it time to build up before I shut it right off because I was freaking out over oil leak too, Was odd that when I put that quart of oil in it, It built pressure but as you know takes several seconds and that seems like several hours when waiting for oil pressure to build, .. I appreciate you guy's helping me look for answers, The guy I got the boat from said he jus had it out 4th July, The mechanic knows him well and said if he had any knowledge of a problem with the boat he would have had it fixed because he has serviced this boat for the 9 years he had owned it and all they have done to it was oil changes, tune ups and winterized and couple solenoids..
Again thanks so much....