5.7 alpha knock please listen

[Tominator88]

Hello, I recently purchased this boat, the owner said it needed a motor (Witch I’ m prepared to do.) But the 2 people that listened to it think it’s something else. there’s no noise at idle, and I have good oil pressure.

 

[Bondo]

Hello, I recently purchased this boat, the owner said it needed a motor (Witch I’ m prepared to do.) But the 2 people that listened to it think it’s something else. there’s no noise at idle, and I have good oil pressure.

Ayuh,...... Welcome Aboard,...... What motor,..?? what drive,..?? what vintage,..?? got a serial number,..??
Have ya tried the broom stick method to locate the noise,..??

 

[Tominator88]

The boat is an 86 with alpha gen one sei drive that is just about broken in motor is a 2011 Mercruiser 357 I haven’t tried to isolate the noise after the water test I was so sure it was the motor that I was done but after speaking with a few ppl I’m not sure just thought I’d get anouther opinion

 

[Scott Danforth]

Get a mechanics stethoscope or the broom handle method works

 

[04fxdwgi25]

Is boat in the water? Only have the noise when underway / under load or in neutral, or both?

So many possibilities to list. engine coupler, really bad alignment of engine / drive, bad U-joints on drive, drive tilted up too far while running, engine bearings.... The list goes on.

You have a video of the noise? Like Scott stated, try to locate general area with a stethescope or a broom handle.

If boat on a trailer, pull drive off, run it (with water going thru it) and see if the noise goes away.

 

[Tominator88]

Only in water when I kick the throttle up when I’m at like 1200 rpm in no wake zone it’s fine start to give it any throttle it starts to me it definitely sounded like the engine but my engine shop machine shop guy and a seasoned boat mechanic that was at his shop watched the video and thought otherwise my intention was to pull motor I have anouther ready to go (but it’s old style will require different intake and flywheel coupler the one I would be pulling is a 1 piece rear seal vortec my engine guy wants me to be sure before I potentially downgrade motors and still here noise when u joints are gone is it loud in the boat ? Everything I’ve read says gimbal bearing would make noise at idle you can’t here a thing Erving in driveway

 

[Tominator88]

Here is the video

 

[Dubed]

Is the prop hitting the zinc on the outdrive?

 

[Tominator88]

Nope

 

[dave8311]

Spark knock, timing way off.

 

[stresspoint]

starter not disengaging completely.

 

[Tominator88]

Spark knock, timing way off.

I was thinking spark knock too but I replaced the ignition module and reset timing it is a est distributor and I used the shunt tool and set it to 10 some ppl say 8 but Mercruiser tech said 10 and I can rev it in driveway and not here a thing

 

[Scott Danforth]

Revving in neutral doesn't mean anything .

Knocking under load is bad timing or bad fuel. Either way it's the motor eating itself

 

[Scott06]

Similar noise this guy said head gasket was leaking water into chamber

 

[nola mike]

Nobody but me thinks that sounds like a rod knock?

 

[Bondo]

Similar noise this guy said head gasket was leaking water into chamber

Ayuh,..... Inspectin' the spark plugs is probably where I'd start,....

If it's detonation, there'll be bits of piston on 'em, 'n the corners will round over,......

If it's a head gasket, one or more plugs will be clean as new,.....

If it's a rod knock, take it out, induce the knock, 'n pull one plug wire at a time, the knock will stop, when ya pull the right plug wire,.....

'n an ole broom stick will help narrow it down,....
Inspectin' the gimbel, 'n u-joints is only 6 nuts away,....

 

[Scott Danforth]

After you pull the drive, if you need to go further, the motor can be out in another 35 minutes

 

[Scott06]

Nobody but me thinks that sounds like a rod knock?

Doesn’t sound like the rod knocks ive seen first hand and those made the noise at unloaded idle. either way hard to diagnose from the keyboard

 

[kenny nunez]

It sounds like something in the flywheel housing.

 

[Tominator88]

Thank for the ideas I do think it sounds just like that guys noise I bought this boat because I had a motor for anouther project that’s not happening but ppl kept telling meme to make sure before I swap the motor and maybe still have a knock not to mention the motor I’m pulling is a later model vortec and my other is a 2 piece rear main seal model tonight I pulled it out I’ll be checking the rods tomorrow I don’t know if I’m hoping it is a rod or not I hope I didn’t pull a motor for an ignition knock