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99 Mercruiser Tapping and Low Oil Pressure

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98SeaRay

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I have a Merc 3.0, Today I noticed that the engine was running well until I got to around 4000 RPM when the engine began to make a tapping noise, at the same time the oil pressure is very low between 0 and 50 PSI......there were normal readings from the engine temp. gauge as well......any ideas?
 
I do not understand what you checked on the CDI. What is a CDI plunger? It would be very unusual for the CDI to be the problem in starting.

Is this motor pull start or electric start? The starting mechanism is a little different in each.

Most likely, you starting circuit in the carburetor is clogged and needs to be cleaned. Also, make sure that the accelerator pump is moving freely ...it is a lever driving a small shiny vertical pin going through a little rubber bellows on the side of the carburetor. It is pushed down when you accelerate from an idle. You should also be able to push it down with you finger to see if it moves freely.

You will need to remove the carburetor, disassemble and clean the passages.

Mike

_________________________________

Gafas carrera
 
...oil pressure is very low between 0 and 50 PSI...
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So, what is it? 35-50 psi is good at 4000 RPM. What weight oil do you use? Is the tapping noise louder if the engine cover is off?
 
-Checked the oil this morning, no milkiness, oil was almost at full line, and it was just changed a few weeks ago still nice and clean

-The tapping noise is louder with the cover off and the oil pressure was around 25PSI constantly even with a increase in throttle, not sure about the oil I had a mechanic do the change at begining of season so I didnt ask.....what are normal readings around full throttle for PSI? I'm going to run it with an engine gauge and see if maybe mine's broken
 
Several factors involved: oil weight, engine temp., engine berings condition. Figure an avg. of 10 psi for every 1000 RPM on a good engine. Tapping could be a loose/worn pulley...see if any of them wobble at idle.
 
guyjg said:
Several factors involved: oil weight, engine temp., engine berings condition. Figure an avg. of 10 psi for every 1000 RPM on a good engine. Tapping could be a loose/worn pulley...see if any of them wobble at idle.
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Thanks for the help I'm going to check this out later when I have a chance to run it. My engine temp is fine, it's sitting rite around 130-150....with low oil pressure would I get a higher engine temp. reading? I know the engine is water cooled so I'm guessing the two have noting to do with one another.
 
ok guys sorry it took so long to get back on subject, been in the process of buying a new home....so I went out today and my oil pressure checked out fine, I'm still getting this tapping sound but I noticed it's more of a 'winding' sound.....guy who went out with me said I should take the prop off and check the teeth to see if it's maybe missing cause its stripped but I feel like it's coming from the engine and not the lower unit.....any other ideas before I start taking things apart?
 
Remove the OD, connect a water source to the inlet, no noise...outdrive issue...still noiey...engine issue.
 
A bad gimbal bearing is such an obvious sound. You can feel a really bad one right thru the starboard side at grease zerk fitting. The sound will follow the engine RPM.
 
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alright so today i got around to taking off the drive and the gimbal is fine, the outdrive checks out fine with everything went over the entire thing with a marine mechanic. So here's where we re at, my mechanic thinks it might be the prop because it was replaced prior to me buying it about a month ago and it might not be the rite size. I, on the other hand think its time to start going over the block and figure this out.....what should I be looking at now?
 
merc manual states:

The used of a stethoscope can aid in locating a noise source, however because noise travels to other metal parts not involved in the problem caution must be exercised. Most Mercruiser manuals have troubleshooting section that has engine noise. it's not the prop be the first time I ever heard of a prop lowering engine oil with out losing rpm's.I use a long handle screwdriver to check for problem areas :cool:.
 
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