Mercruiser 43L help

"I have a mercruiser 4.3L with

"I have a mercruiser 4.3L with about 500 hours on it, stock besides a 4bbl carb swap. At certain rpms mostly above 2600 you can hear this weird rattling or pinging coming from the block. At first I thought it was bearings, but i have around 25lbs oil pressure at idel. I just replaced all the plugs, same noise. Could the timing be off and that noise be pinging? Thanks for the help!"

"It could be pinging, especial

"It could be pinging, especially if the gas is old. If you don't do the work on the boat yourself, find someone you can trust and have them verify that the timing and other adjustments are correct."

"I do most of the work on the

"I do most of the work on the motor myself as I'm not afraid to turn a few wrenches! Half the fuel is racetrack 87oct, and the other half is shell V power."

"I don't know how old the

"I don't know how old the gas is but 87 is nothing to get excited about, race gas or not. Never knew they sold 87 octane at tracks but that's too low. What octane is V power? You should be using at least 89 octane and if it sits for any length of time, add 93 because of the drop in octane over time. Higher octane if it's hot and dry."

"I'm not sure what else it

"I'm not sure what else it could be making that noise, I dont wanna use it and have the motor blow! Shell V power is 93 octane, but the noise I'm hearing is actually pretty loud which kind of worries me..."

Jim - Race Track is a brand of

Jim - Race Track is a brand of gas/convenience stores found primarily in the southeast.

sounds like detonation. does it completely go away at idle? collapsed lifter?

"I can still hear it at idle,

"I can still hear it at idle, but not so much. Sounds like a clinging noise, wish I knew what it was!"

"Take a 4 foot piece of water

"Take a 4 foot piece of water hose, put one end up to your ear and trace the other end all over the engine until it gets louder, you would be getting closer to the source. Be careful of turning fan belts!! Have someone with you to run the boat while you "scope out" the noise. I have found many agrivating noises this way on cars and boats. Good luck! Had a starter motor do this one time on a Merc 470. The bendix would move forward and the teeth would touch the flywheel teeth once in a while. I had a repair shop install another washer on the armature to prevent it from being so close to the engine flywheel when it was not engaged"

Sounds like it is deff coming

Sounds like it is deff coming from the block... It seems to get worse the longer the motor is running too.

"Once you rule out the bad gas

"Once you rule out the bad gas issue, some other possibilities are: bad gimbal bearing, circulation water pump, PS pump, loose flywheel bolts, bad coupler, bad U-joints.
You need to identify if it is coming from the front or back. If it seems centered in the block, it sounds like you will need to pull the engine and tear it down. The longer you run it the more potential you have for serious (read "expensive") damage.
Good Luck,
Rod"

"To expand on the gimbal beari

"To expand on the gimbal bearing, it sounds kind of like rocks or ball bearings bouncing around. 500 hours is pretty low for that to go bad but it is possible.

The compression should be tested and while the plugs are out, they should be inspected for the color of deposits. Tan is good, brown is OK but anything else can indicate a problem. I would still verify the timing, too."

"Hmm it does king of sound lik

"Hmm it does king of sound like bad ball bearings now that I think of it. What exactly are the gimbal bearings? When I changed the plugs today the old ones were black... Thanks for all the help, you guys are great!"

"I would like to add that a lo

"I would like to add that a local marina replaced all the boots, but I noticed that if the drive isnt more than half way down and u rev it above 2000 rpms the drive makes alot of noise. Would the gimbal bearings make noise while the boat is in neutral also?"

"The drive shaft is rotating a

"The drive shaft is rotating anytime the engine is running, and a bad gimbal bearing will be noisy at any time, idling, or at any speed. Sometimes they make more noise when you are in a turn at low or high speed, sometimes not. This bearing can go bad if it has not been greased regularly, or if water has gotten to it.
With the engine idling at the dock, you should hear the sound quite pronounced at the very back of the engine. This would indicate gimbal bearing very likely.
To change it you will have to pull the drive, and pull the old bearing with a slide hammer. Not tough to do, but you should get a service manual if you plan to do it yourself.
Rod"

"[b]"but I noticed that if

""but I noticed that if the drive isnt more than half way down and u rev it above 2000 rpms the drive makes alot of noise. "

If you've been Screaming that motor at 2000rpms, in Neutral,....
With the Drive any Higher than the Trim Limit,......
You've Probably Torn Up the U-Joints,+ the Gimbel Bearing.............

In Neutral, Without a Load,.... 1500rpms is Too Fast,...... Muchless 2000rpms......."

I never run the engine with th

I never run the engine with the outdrive any higher than the trim position. I think clinging noise I'm hearing is coming from the motor itself too. Maybe I should upload a video/sound clip?

"20 Baja-

Have you checked

"20 Baja-

Have you checked the timing, cap/rotor/plugs/looked into the spark plug hole to see carbon deposits on the pistons? Take a fuel sample and look for water or other garbage, check your oil, compression and vacuum, firing order, plug wires, try to run it on a different source of gas and then ask what the possible causes could be. I haven't seen anything that shows what has been checked and over the internet, all we can do is guess until we know what has been done to find the cause.

A compression/vacuum test can find a lot of things and indicate the general health of the motor but apparently, that hasn't been checked yet. Burnt valves can sound just like what you describe and if you hear a ticking sound from the side(s), it could be as simple as an exhaust leak.

You're not giving us much to work with."

"Before I got into a big panic

"Before I got into a big panic I would pop off the exhaust turndowns and check the flappers. They have been known to make more than their share of noise.

Also, a mechanic's stethascope is an invauable and inexpensive tool for checking these kinds of noises.

Good luck,
Rick"

"I did notice there was alot o

"I did notice there was alot of carbon on the old plugs when I changed them. I honestly havent checked the fuel filter in about 5 months, but I've only ran about 60 gallons through it. If it is a burt valve, I have a bunch of them from another 4.3L, its just wether or not I want to do the work myself. I honestly sounds like a rattle of some sort. The boat is firing on all cylinders, and runs great though."

"you can have significant rod

"you can have significant rod noise and still have oil pressure, btw. I've seen it."

"Perhaps pull the oil filter &

"Perhaps pull the oil filter (you don't need to drain the oil necessarily), and cut the outer can off and inspect the pleats closely for metal particles. If you don't find any, chances are good the major engine parts are healthy.
Best way to cut the outer can off is with a heavy duty can opener, or make a hole near the base of the outer can, and use tin snips to finish around the base. You can then use a sharp knife and cut around the top and bottom of the pleats, then expand them and lay them out on a flat surface. Use a strong light for inspection.
Note that a few very tiny metal particles are fairly normal, but if you find anything metallic bigger than a grain of salt, you have a problem.
Hope you find nothing big!
Rod"

"[b]"I honestly haven'

""I honestly haven't checked the fuel filter in about 5 months, but I've only ran about 60 gallons through it."

It doesn't take much Water to restrict the Filter,.....
That Alone can cause a Lean condition,+ Detonation........
That'll Burn the Pistons as well as the Valves....."

"I didnt find any particles in

"I didnt find any particles in the oil which is a good sign, but I couldn't get the fuel filter to unscrew. I'm going to have to try and find my oil filter puller to get it off... When i ran it the other day it only made noise above 3200 rpms, and what I was hearing was pretty loud. I'll see if I can get that fuel filter pulled, i want to get this fixed by the weekend for the p0ker run here!"

"Hey all. Just joined, was loo

"Hey all. Just joined, was looking for any similar noises of 4.3L Mercruiser after I ran our boat and heard a rattling sound.

Here's the story: new deckboat bought last year probably has only a couple dozen hours on it. Began taking the boat out on the water a month ago used most of the gas, added only 7 gallons to put some fresh gas in. Places on water were closed, one accepted the little cash ($20) I had and gave me some.

Well, yesterday I took the boat out and idled a few minutes while I put the canopy down. I noticed a loud rattle sound, figured it to be canopy supports hitting against each other. Wasn't... was in the engine compartment. Opened it up and isolated it (possibly) to the leftside valve cover.

In gear and throttled up a bit the noise quieted, more RPMs and it wasn't heard at all.

Went back to dock and drove to gas station for 10 gallons and STP fuel treatment (using partial bottle). Put out onto the water again, idled and nothing heard.

Conclusion: bad gas...? That's all I can figure it could be. Interestingly, the oil pressure was showing 60 when the noise occured. Read about 50 after the fresh gas. Overheated oil maybe, or something else? Water temp always said normal, middle of the gauge (when warmed motor).

Needless to say I'm going to check into this more next time.

BTW, AFAIK this engine with the 2V TKS carburator might not have any anti-knock adjustment (sensor?), but the Multi-Port Injection ones probably do. I thought that could be part of the problem, or rather an incapability to prevent such events-- if it is knock/ping.

Anyway, hope this is of some help to this thread. Not intending to hijack it, just seemed a similar situation.

Thanks for this message board, could prove a good source of info for me from the looks of it!"