4 hp Nissan strange noise.

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Shane0524

Seaman
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Jun 24, 2012
Messages
52
What is the strange buzzing/humming coming from my 4hp 4 stroke tohatsu outboard?
It does it at all speeds, a little less at idle, but some times it will do it and some tines it won't, it doesn't do it all the time, also when it does it I will put it in neutral and it stops but other times neutral doesn't stop it and I have to turn off the engine to make it stop. Please help me with any ideas also when it does the noise it still pumps water,so I don't think it is an impeller but it doesn't not sound like metal on metal.
 
pvanv

pvanv

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Re: 4 hp Nissan strange noise.

What is your actual model and serial?
 
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Mojo22

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Jun 26, 2012
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Re: 4 hp Nissan strange noise.

I think I have the same problem on my 6hp version. It's a strange situation in that the whine/howl/buzz does not appear to be RPM related. When I rev my motor the pitch of the whine/howl/buzz does not seem to change. How can this be? What part of the motor assembly turns at a constant speed? Mine will occur after the engine is warm and under light to medium load. Using a mechanics stethoscope I've isolated it to the head unit area. To me it sounds like two large gears grinding against each other with no lubrication.

Shifting in reverse or neutral does not always make the sound go away - but sometimes it does. Yesterday I could not get the noise to stop until I shut the motor off, then restarted it. Then it was fine for the next 20 minutes. Are you experiencing any of these same symptoms?
 
pvanv

pvanv

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Re: 4 hp Nissan strange noise.

I didn't hear much that wasn't normal, except around the 16-second mark, and then only for about 1 second. Was that a plane flying overhead, or did the growl come from the motor?
 
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Shane0524

Seaman
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Jun 24, 2012
Messages
52
Re: 4 hp Nissan strange noise.

it does it solidly from about 11 to 15 second mark. And yes that noise came from the engine.

and I replaced the impeller, fuel filter, and changed both the oils UU, LU
i ran it in a bucket and it all seemed fine although i could not really put any load on it so i don't know if it is still going to do it or not.
 
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Mojo22

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Jun 26, 2012
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Re: 4 hp Nissan strange noise.

Shane - that is the EXACT sound that my 6hp is making; however, it will go on for 10 minutes at a time unless I reverse gears (fixes about 50% of the time)) or shut it off and restart (fixes about 75% of the time). I will try and record my sound and submit for further analysis. Glad to hear I'm not the only one with this exact problem!
 
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Shane0524

Seaman
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Jun 24, 2012
Messages
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Re: 4 hp Nissan strange noise.

Mojo22 said:
Shane - that is the EXACT sound that my 6hp is making; however, it will go on for 10 minutes at a time unless I reverse gears (fixes about 50% of the time)) or shut it off and restart (fixes about 75% of the time). I will try and record my sound and submit for further analysis. Glad to hear I'm not the only one with this exact problem!
Click to expand...

same here glad to know I'm not alone.....hopefully Paul knows what it is, says he's a certified tohatsu tech
 
pvanv

pvanv

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Re: 4 hp Nissan strange noise.

Gotta say I never had a 4/5/6 make that sound. Sorry.
 
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Mojo22

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Jun 26, 2012
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Re: 4 hp Nissan strange noise.

Was finally able to capture my similar noise Shane.

http://youtu.be/Lik66OmD_FI


When I started recording the noise had already started, but you can clearly hear it stop once I place the trans in neutral. I reved the engine just to demonstrate that it is not (seemingly) RPM related. After placing back in gear the noise did not return for about 10 minutes.
 
TOHATSU GURU

TOHATSU GURU

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Jul 22, 2004
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6,164
Re: 4 hp Nissan strange noise.

Probably a harmonic due to the application. Not unusual on an undamped auxiliary bracket or on an aluminum boat. Throw a piece of carpet or sheet of rubber over the bracket and see if that solves it.
 
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Shane0524

Seaman
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Jun 24, 2012
Messages
52
Re: 4 hp Nissan strange noise.

mine i mounted on an inflatable dinghy and it has been for years but recently stated doing this. so i don't know it that would be it or not?
 
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Shane0524

Seaman
Joined
Jun 24, 2012
Messages
52
Re: 4 hp Nissan strange noise.

exactly the same noise yours was a bit more persistent than mine but no one seems to know what it is. Are you going to take it to the dealer?
 
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Mojo22

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Jun 26, 2012
Messages
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Re: 4 hp Nissan strange noise.

I have taken mine to a repair shop in the past but they could not duplicate the problem; however, I don't think they ran it long enough. I found the noise now begins after 10 minutes at light to medium throttle. Yesterday I used a mechanic's stethoscope but could not really isolate it. Sounded like it was coming from both the powerhead and the midsection - gear grind type noise. The fact that it's not RPM related really stumps me.
 
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Shane0524

Seaman
Joined
Jun 24, 2012
Messages
52
Re: 4 hp Nissan strange noise.

same with mine it does it all over and is impossible to make it do it on que it just does it when ever it wants
 
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Mojo22

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Joined
Jun 26, 2012
Messages
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Re: 4 hp Nissan strange noise.

Something is different! Installed a new "hi-thrust" prop (8.375x6 elephant ear) and cruised for over an hour today. NO NOISE. Not sure if the problem is solved - didn't think it was a slippage issue - but so far everything is sounding fine. Stay tuned for updates.
 
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