06 Mercruiser 3.0 issue

[SamuelP63]

Good evening folks.

I've got an odd issue... possibly a simple one to you guys.

Alright, here's my story. Today we did a normal boat day. Lakes were down a bit and bumped bottom in one of the canals. A few lakes, couple hours, later i went from idle to open throttle to get on a plane and heard a grinding noise. I immediately pulled it to neutral. My first thought was spun hub. I tested it... all good. I tried to duplicate a few times with no luck. Thought i was losing it. Put a few people on the boat later in the day and it came back under heavy acceleration... i shut it down to inspect... nothing. When i started it up, i put it in neutral and bumped the throttle to start it... immediately heard the noise. Pulled the motor cover. In neutral and throttle up it was an immediate grinding noise. It didn't appear to be the alternator... and not sure that would make sense as it only happens in neutral and under heavy load. No loss of power. No symptoms. Just the noise... it appears to be internal.

Any help would be appreciated?

Thank you,
Sam

 

[Scott Danforth]

grinding noise, or the sound of marbles in a tin can?

the later is pinging or detonation and is the sound of your motor eating itself under load

either you have crappy quality fuel, or your timing is off.

 

[SamuelP63]

Marbles may be a better explanation. Sounds more like a vibration. I checked all motor mounts. All solid. Sounded like possibly alternator.

What kills me is why it is happening under heavy load and in neutral... but I can run wide open and it sounds flawless.

Thank you for the response. I'm planning on dropping the oil to look for metal... but wanted to throw it on here first to see if I could narrow it down.

 

[SamuelP63]

It's got to be a clutch related issue right?

 

[Scott Danforth]

your clutch is a dog clutch in the lower unit of the outdrive. doubt it is the dog clutch

when was the alignment checked last?

did you smack the oudrive into something?

 

[merc850]

When was the last time the outdrive was removed and the U joints greased? If it's been 2 or more years it's time.