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2003 merc 115 efi clunking sounds from lower unit

E

eric80

Regular Contributor
HI, just brought my " new to me" boat home last night.
I'm fired up, it's been a long search for this boat and motor set up.

When on the hard (in the driveway) last night I fired it up with water keeping the water pump wet.
when I put it in gear I get some intermitent clunking noise coming from the lower unit. no noise in netural, just in forward and less noise but a bit in reverse.


there are a couple of whacks (dents) in the stainless steel prop. when the prop is turning it is a little bit out of balance, not bad, but enough to see.

It was getting dark so haven't checked the gear oil and or if there are metal fragments, will do that today.

I did read on some posts that it's not unusual for some motors to make some lower unit noise when not in the water as there is no pressure on the prop.

I'm writing this to see if this is normal on my motor.

any comments?

cheers
 
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I put it in gear I get some intermitent clunking noise coming from the lower unit.
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A few clunks when shifting into gear (do it quickly) is normal. Continued clunking after the shift says a problem exisit. If that is the case then LU may have some damage from the prop hitting a submerged object then running a damaged prop.

there are a couple of whacks (dents) in the stainless steel prop. when the prop is turning it is a little bit out of balance, not bad, but enough to see.
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Get that prop refurbished before going to the lake. Make sure the prop shaft is not bent.
 
Hi Thanks
I called Merc. they also said once in gear there should be no noise.
So I drained a little oil to check for metal and found none.
The oil level was down a bit, couple of ounces.
Vent and filler plugs were tight and the rubber seals were in good condition, no evidence of leaking
filled it up and noise went away.
Out on the lake motor preformed well and back in the driveway no noise after our run.
I will completely drain gear oil and replace to insure no water in the system.

Could the noise have come from low oil? A bearing starting to go? intermitent issues from the prop damage?
 
Probably not a bearing - my guess would be the clutch dog making the "clunk" - it could have some worn ears that the lack of oil made sound worse. (that would be my bet)
 
It will make a few clunks when on a hose as the rpm is not steady and no load on prop, the 25-50 rpms your dont see on tach are reflected in prop as it speeds up and down making a clink/clack in gear ,it will stop when it has a load on it in water. Also if it has a plastic hub prop if not torqued to 150 it can cause this but in water only..
 
Hi so I checked the gear oil, no metal, but the level was down a couple of ounces.
once topped up no noise.
I will once I get to a shop replace the existing gear oil just to be sure.
 
I will once I get to a shop replace the existing gear oil just to be sure.
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Changing the oil is to easy to pay someone. Check on YOUTUBE and you'll find videos demonstrating how to do it.
 
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