Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha One

Status
Not open for further replies.

thecca

Seaman Apprentice
Joined
Jul 7, 2013
Messages
42
Hi... I went on the water yesterday and noticed a strange sound coming from engine bay under acceleration / trying to pull a wakeboard/tube out of water. Sound is pretty weird, it's like a rattle and I can compare it to pieces of change in your clothes dryer, it clangs, like if there was some metal parts in the motor/transmission that were broken and flying around, but the motor does not lose any power and runs smooth like usual. Sound started saturday randomly and wasn't there before even with 6 people in the boat and a wakeboard in the back.

What do you guys think? Someone at the marina said the motor probably needed to be changed, but I doubt it? I mean, it happens only on accelerations. I checked oil and it's still clear and full. It doesn't heat and the oil pressure is good. Checked for some lose parts and everything seems fine... Once it's at cruising speed and on idle motor runs fine.

Transmission / Drive gears are Edit; up? Motor can't withstand pressure (acceleration)? Could it be the timing?...

Thank you.

Mercruiser 3.0L (2000) with Alpha One - Weird noise (clang / rattle) under acceleration - YouTube
 
Last edited:

alorio1

Seaman Apprentice
Joined
Jul 1, 2013
Messages
34
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

Check outdrive oil level, grease gimble brg, check prop nut for tightness and run the highest octane gas. You could be hearing pre-detonation rattle from low grade of gas. My 3.0 will diesel if I don't run premium fuel and can hear a slight predetonation noise with low grade fuel.
 

Reming870

Petty Officer 2nd Class
Joined
Jul 15, 2010
Messages
191
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

Could be pinging from fuel. Try an octane booster or changing to a premium fuel. Confirm timing. My 3.0 L with poor fuel sounds like it has marbles in it.

Or, just change the motor and see if the problem goes away. At least you'll have a spare motor if it doesn't. :)
 

thecca

Seaman Apprentice
Joined
Jul 7, 2013
Messages
42
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

I switched from 91 to 87 octane gas 1 week ago (manual says it's tuned for 87 (regular) so I did put some in it...) For the outdrive, everything was checked and some parts were changed in last feb. so I doubt this is my problem... Unless the gears are bad but the problem really seems to come from motor..

Anything else? I don't think I will change the motor since it's a bit expensive lol... For the timing, I need to see if cam gear is aligned correctly in the timing chain?

I've read that a broken flywheel dust cover could do that? But would it do it ONLY under load?
 
Last edited:

Howard Sterndrive

Rear Admiral
Joined
Nov 5, 2008
Messages
4,603
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

I'd do the easy thing first- pull the drive and feel the gimbal bearing and look for slop in the u joints.
Getting your head back there with the doghouse off while someone else accelerates might be something to do to. Watch to make sure the engine mounts aren't loose or worn letting the engine twist further than it should. If it's moving around, the coupler could be hitting the rear engine cover under acceleration.
 

thecca

Seaman Apprentice
Joined
Jul 7, 2013
Messages
42
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

This doesn't sound like it's coming from the drive... Sound is in the engine bay area... The joints were changed last february, I'll take a video tonight and post it.
 
Last edited:

Reming870

Petty Officer 2nd Class
Joined
Jul 15, 2010
Messages
191
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

I think you may have answered your own question:

"I switched from 91 to 87 octane gas 1 week ago"

Strange coincidence the problem surfaced shortly thereafter??? Tuned for 87 or not, how can you ever trust the quality of the gas at the pump?
 

thecca

Seaman Apprentice
Joined
Jul 7, 2013
Messages
42
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

I doubt this would make this kind of noise. I mean, knock or ping is not THAT loud.

Gas is good, I fuel at the same place since a couple of years and got the same fuel in my car, everything is fine.

I will take a video tonight and keep you updated. Thank you for replying.
 

oldjeep

Admiral
Joined
May 17, 2010
Messages
6,455
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

Could be that you had a rocker arm nut come loose. Had that happen once on my old 3.0L, eventually instead of just making noise the rocker flipped 90 degrees and made the boat stop running. One $2 stover nut and a valve cover gasket later it was back to working.
 

thecca

Seaman Apprentice
Joined
Jul 7, 2013
Messages
42
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

Did the issue only appeared under load? (When accelerating) Because if the engine is not ''straining'', everything is fine and motor runs A1... I think that may-be my timing gets off when engine is hot and under load...?
 
Last edited:

thecca

Seaman Apprentice
Joined
Jul 7, 2013
Messages
42
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

...
 
Last edited:

thecca

Seaman Apprentice
Joined
Jul 7, 2013
Messages
42
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

The grimble bearing was also changed in february. I heard the new ones don't need to be greased. The U-Joint seems OK since it's not making any noise when I'm turning and no water is getting into it (well, as far as I know). I've tried pulling the trim up and it didn't solve the problem. Put some octane booster and it didn't help either. Sound is really coming from the flywheel area. Timing may-be?

See video here : You can clearly here something wrong around 1:45 : Mercruiser 3.0L (2000) with Alpha One - Weird noise (clang / rattle) under acceleration - YouTube
 
Last edited:

Grub54891

Vice Admiral
Joined
Jun 17, 2012
Messages
5,908
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

Flywheels do come loose,not often but it does happen. Pull the starter,check the flywheel. Other than that,lifter's? Adjust them next.
Grub
 

thecca

Seaman Apprentice
Joined
Jul 7, 2013
Messages
42
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

Can I just remove the drive to check it or I have to pull the motor out? It's in the back of the engine next to the wall, this is a tough spot to get into.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,465
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

Can I just remove the drive to check it or I have to pull the motor out? It's in the back of the engine next to the wall, this is a tough spot to get into.

Naw,.. Pull the Starter to access the flywheel,..
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,304
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

my first thought is fuel since it is only under acceleration and only since you went from 91 to 87

put some 91 back in it. if the sound goes away, then you were detonating.

if the sound is still there, then move on to mechanical issues.
 

thecca

Seaman Apprentice
Joined
Jul 7, 2013
Messages
42
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

I've put some octane booster so I think it'll do the job... I ran it a while yesterday and the issue still appeared. I fear I might hurt something else if I don't do something soon... If it's an easy thing to fix, I don't want this to break other expensive parts...

Also, could somebody explain me why a broken flywheel cover could rationally creates this sound? I mean...
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,465
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

I've put some octane booster so I think it'll do the job... I ran it a while yesterday and the issue still appeared. I fear I might hurt something else if I don't do something soon... If it's an easy thing to fix, I don't want this to break other expensive parts...

Also, could somebody explain me why a broken flywheel cover could rationally creates this sound? I mean...

Ayuh,... If it's Detonation, you'll be replacin' the motor soon,...

I use spark plug Color to diagnose lean or rich conditions,...
 

thecca

Seaman Apprentice
Joined
Jul 7, 2013
Messages
42
Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

I don't think a detonation / pre-ignition could do that kind of noise, not that loud though... It's coming from the flywheel zone, not the head.
 
Status
Not open for further replies.
Top