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1999 50 liter Apha 1 engine noise

J

jmark

New member
"1999 Crownline 192 Br with a

"1999 Crownline 192 Br with a 5 liter Mercruiser Apha 1. The fuel system / carb had been giving me problems so the local repair shop rebuilt the carb and changed the oil pressure sensor that tells the fuel pump it is okay to run. I was giving the boat a lake test this weekend by running about 25 - 30 miles an hour in a large loop and then idling down to make sure the engine would not stall at low speed. The boat ran fine for about 20 minutes and then a metal on metal noise (like a hammer tapping inside the engine) began. The noise is intermittent but definitely pronounced. I slowed down to no wake speed and was able to make it to the dock. The noise is there regardless if the prop is in gear. The engine oil is only about one month old. Any ideas?

thanks,"
 
Oil pressure? oil in engine? r

Oil pressure? oil in engine? rod cap coming loose.whatever it is do not run again til found.
 
Could be the exhaust water shu

Could be the exhaust water shutter. Same thing happened to me. Both port and starboard worn out. Half the butterfly was clanging around.
 
"Can you tell if it is coming

"Can you tell if it is coming from the engine or the drive?

Gimble bearing will make a roaring or grinding noise. Rod cap - not likely. U-joint - maybe but doubtful.

Sounds like a hydraulic lifter tapping - makes an unnerving little metal on metal tapping noise that sometimes comes and goes. Hydraulic lifters pump up with oil pressure and expand - thereby eliminating the short term need to adjust the valves. When an air bubble or crud gets hung up in a lifter, it may tap for a while. Air would have been introduced to the oil gallery when the pressure sensor was replaced, btw.

Hopefully it will go away, but if it doesn't you can ruin your cam in the long run. Quick fixes include adding a quart of ATF to the oil (automatic trans oil... thin highly refined oil with detergents).

At any rate, this is just a guess. Start with the basics. Go get yourself a test gage and check oil pressure cold and as it warms up and check against specs.

Just thoughts from a car guy. Let us know what you find out.

D"
 
"David,

The noise seems to

"David,

The noise seems to come from the area directly
beneath the intake manifold in front of the carb."
 
I am going through the exact s

I am going through the exact sme thing with a 91 5.0 I have 30 hours on a rebuild. I thought it was a lifter so I changed all of them to be on the safe side but that didnt work. My next guess is a rod or main bearing. All I know is I can not find it. I am thinking I am going to pull the motor and check the flywheel. ????????????????????????????
I am at a loss because it still has power and was running on plain when it happened and I didnt loose any power?????????????
 
"I had metal on metal noise, m

"I had metal on metal noise, more when cold. So I took engine apart and I found a shrunk piston. This was due to a burnt exhaust vavle, which heated up cast aluminum piston and they shrink when overheated. So check compression. Good luck."
 
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