1987 Mercruiser 3.0 Weird noise-what is it?

[UNSUREBOATGUY]

1987 Mercruiser 3.0 with alpha 1. Weird noise that I can't seem to figure out. I'm no boat or engine expert so please go easy on me. It usually only appears between about 1400 rpm and 2500-2800 rpm. It usually goes away at idle, though it didn't for this video for some reason. The engine wasn't quite warmed up all the way-maybe that had something to do with it?

Doesn't seem to matter if the engine is under load or not. I really noticed it mainly on muffs in the driveway because I do not usually spend much time in this rpm range on the water. (I don't rev it up that high on muffs either, but as I let it warm up around 1200 rpm, sometimes it would creep up a little and start making the noise-that is how I first noticed the noise.) I don't ever notice it accelerating-not sure if it is because of the engine working hard or not.

I replaced the exhaust shutter, thinking maybe that was the noise. Didn't make a difference. I cleaned and lubed the dizzy weights to be sure it wasn't caused by sticking advance. They move really nice now, but no difference in performance. I do not have a timing light, but the engine seems to run pretty much perfect, so I figured it was correct. I can certainly get a light and check timing if that would be helpful.

http://www.youtube.com/watch?v=1JMjMg0uto8

Please let me know what you think. Thanks a bunch.

 

[BAproject]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

Is your starter disengaging after you start the engine. It almost sounds like you're turning the key with the engine running.

Also, and it happened to me which is the only reason I'm saying it, have you checked the power steering fluid level? That's probably not it, but won;t hurt to check it

-BAproject

 

[HT32BSX115]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

Howdy,


It's VERY difficult to diagnose noises via video.....


Now having said that, how many hours are on the engine and drive?

Have you had the drive off? (ever?) did you look closely at the u-joints and gimbal bearing?


Have you had the belt off and turned the alternator and circulating pump by hand? ( I didn't see a power steering pump)

When you do, grab the damper (crankshaft pulley) and give it a good pull (loose or "sloppy"?)

Just some things to check......


For an 87, that engine looks REALLY nice and clean!!


Cheers,


Rick

 

[EddiePetty]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

....maybe my old eyes are playin' trick but that alternator fan seems to be running out (just a few quick glances in the video).

Drop the fan belt for just a moment and see if the noise disappears.

Also, why is the #1 plug wiggling around so much...loose connection?

 

[UNSUREBOATGUY]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

UPDATE: Thank you for the quick replies. I'm sorry if this further confuses things, but we had the boat out today and never heard the noise under load. When putting around very gently, it made the noise momentarily at around 1500 rpm ish, but went away almost immediately. I'm thinking now that the only times I heard the noise on the water in the past is under very rare and specific situations. I ran the boat at all speeds today, accelerated slowly, idled around, did a fair amount of cruising, etc. It makes the noise in neutral, but not under load. The noise does seem to be from the back of the engine/flywheel area, but it's hard to pinpoint.

It's almost like a metallic rattle/vibration noise. I see why you would say it might be the starter, and I thought of that too, but would that be pretty obvious and not be affected by load, etc.? There is no power steering, and I am pretty sure it is not the alternator, unless just the vibration of runout might cause a harmonic rattle?

The gimble bearing and u-joints are new-I did them this spring as part of my new-to-me-boat-fix-up (bought the boat last fall). The bellows, impeller, gear lube, alignment, new alternator, fuel pump, plug wires and starter were part of the project as well. Sorry-more info than needed, but a little background anyway.

I don't know how many hours are on the setup, but my wild guess is that it hasn't been used that much. Apparently it sat for two years before I got it. It seems that it was pretty well taken care of up to maybe the last owner or two before me, and they didn't keep it very long.

I'll look into play on the crank shaft pulley-didn't think of that one. Not sure on #1 plug-as far as I know everything is fine there.

Thanks again for all the input guys. I'm one of those guys that that checks out every stray rattle or buzz on the cars, so I hope I'm not making a big deal out of nothing, but it is a pretty loud noise and it bugs me that I don't know where it's from. Just want to be sure it's not a symptom of something major looming in the future and if so I'd like to catch it early.

 

[UNSUREBOATGUY]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

anyone hear a noise like this before?

 

[cr2k]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

Did you pump some grease in the gimbal brg? maybe that will help. About 15-20 pumps. Cuz if you didn't fill it up with grease when you changed it it may be about dry.

 

[Adirondack]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

For the heck of it, when the engine is running feel under and behind the manifold between cylinder 2 and 3 for an exhaust leak. Manifold gaskets seem to like to burn there, and a small exhaust leak can sometimes sound like a "tick". Not saying that's it, but just throwing out ideas.

 

[UNSUREBOATGUY]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

I'm pretty sure I got the gimble bearing filled up properly. I kept pumping while turning it by hand and it came oozing out a little all the way around.

Almost seems like something is loose and rattling back by the flywheel cover, but when I feel around back there, it seems like everything is tight.

Is this something I should be worried about, or do these engines just have harmonic rattles sometimes? Thanks for the input guys.

 

[HT32BSX115]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

I am the same way. I don't like noises and rattles....

Almost seems like something is loose and rattling back by the flywheel cover, but when I feel around back there, it seems like everything is tight.

Makes me think of the flywheel bolts and a possibly loose coupler.

 

[UNSUREBOATGUY]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

Is there a good way to check the flywheel and coupler with the motor in the boat? Do I just stick my arm back there and grab the coupler? (Battery disconnected) Is there a reasonable way to get the flywheel cover off to check the bolts?

Thanks again.

 

[HT32BSX115]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

Do I just stick my arm back there and grab the coupler?

You might be able to do that but I'm not sure you would feel anything amiss.....




I have a hard time believing that the flywheel bolts are loose......but stranger stuff has happened.


To get to it, the proper way would be to pull the drive and THEN pull the engine.


Before you do that, you might just pull the drive and run it briefly and see if it still makes the noise. (hook a hose to the gimbal water input if you want to run it long enough to heat it up.)

Sterndrive packages have a tendency to transmit noises from the drive into the engine compartment.

 

[UNSUREBOATGUY]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

Hmmm.........what does it sound like when the starter doesn't disengage all the way? Is this something that might come and go depending on rpms? Doesn't make sense to me, but that doesn't mean much

 

[HT32BSX115]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

Hmmm.........what does it sound like when the starter doesn't disengage all the way? Is this something that might come and go depending on rpms? Doesn't make sense to me, but that doesn't mean much

I don't think your starter is NOT disengaging......that usually sounds REALLY bad because the engine continues turning the starter after it starts...... rev it up and the starter usually disintegrates....

 

[UNSUREBOATGUY]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

By the way, I just loosened up the belt to see if all the pulleys spun smoothly and to check for play on the crank pulley-everything seems fine. The belt was maybe a little loose though. Hmm.

 

[UNSUREBOATGUY]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

One other thought-when I replaced the exhaust shutters, I found that all that was left of the old ones was the cross bar. I pulled off the drive and had the exhaust tubes inside the boat removed so I could replace the shutter and I looked hard for the steel pieces of the old shutters in the exhaust pipe and the drive. i never found them. I assumed that the PO removed them as the exhaust tubes in the boat seemed fairly new. I even poked a stiff wire around in the exhaust pipe from inside the boat, through the exhaust bellows and through the relief ports looking for the shutter pieces. Is it possible there is somewhere one could be hiding and making the noise? I might just be grasping at straws here.

Are there any other symptoms that might lead one to believe that the flywheel or coupler are loose? The thought kinda scares me.

 

[UNSUREBOATGUY]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

Looking at the manual-it looks like I can remove the flywheel dust cover to check out the flywheel. Do my symptoms point towards a loose flywheel or coupler? I'm trying to avoid pulling the engine only to find I have a loose cover or something silly like that.

 

[redjmp]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

I seem to be having the same issue with my 5.0L. Sounds like a rattling from the back but more so toward the port side.
Did you ever find the problem?

 

[Bt Doctur]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

If the dust cover is metal, it`s most likely cracked.Produces a intermittant vibration type noise

 

[UNSUREBOATGUY]

Re: 1987 Mercruiser 3.0 Weird noise-what is it?

Update: if it might be helpful to anyone. I took the flywheel cover off to check the flywheel-that seemed fine, ring gear in great shape, nothing loose, etc. There was a little gunk in there-high water level at some point? The only thing I did find was that there was a short crack or two in the flywheel cover, and i figured that must me where the rattle is coming from. I adjusted the timing a little during tune up-it was a little off. This seemed to make it rattle a bit less. Bottom line is it seems to have just been the flywheel cover. It still makes the noise occasionally in neutral around 1200-1500 rpm, but it doesn't appear to be a real problem. The boat has been running great this spring. Thanks guys!