low RPM growl

[Searayguy185]

I've noticed that around 800-1000 RPM's there is a quite "growl" coming from the lower unit. At the same rpm when it's in reverse or when i advance the throttle in neutral I don't here anything. Also when i run that rpm on a hose out of the water with the prop spinning I don't here anything. Someone thought it was just "prop noise".

 

[RollerCoastr]

When was the last time you had a look at the gimble?

 

[Searayguy185]

I've personally never looked at it. I bought it at the end of 2015 and now has 200 hrs on it. I was told that this boat being a 04 is to new to worry about gimbal bearings. Wouldn't it make noise at same rpm in reverse? Or even in neutral?

 

[RollerCoastr]

Typically yes, since the gimbal turns with the engine but it's my first go-to when I hear "growl". I don't agree that 2004 is too new though. I've known boats that have had gimbal problems covered under warranty.

 

[BillK2632]

Sounds like it could be the gimbal bearing. If greased properly and the bellows never leaks to get it wet it can last indefinitely (my 1999 has the original gimbal bearing). But they can and do wear out and tend to make a growling sound when they do. Some of the new ones are sealed so you don't grease them. Yours probably has a grease fitting on the lower right side of the transom assembly (outside of boat) if it does give it 4-5 pumps with a quality bearing grease like Quicksilver Extreme Grease. See if that quiets it down. The growing will get louder and louder if the bearing is failing, to inspect you need to pull the drive and turn it by hand feeling for a roughness as it turns. The good news is once the drive is off the bearing can be easily replaced. It's also a good time to inspect the bellows, lower shift cable and trim senders. It is common to replace all at the same time. If this has never been done on your 2004 it could be time.

It is curious that it only growls in FWD, since the input shaft spins all the time you usually hear the gimbal growl in F-N-R.
But greasing the gimbal can't hurt, I would start there.

 

[KevinC]

[QUOTE="... I was told that this boat being a 04 is to new to worry about gimbal bearings...[/QUOTE]

It's never too early to worry about gimble bearings. When I had my 2003 260DA I had the gimble bearing replaced about 4 years ago. The bravo sterndrives are quite heavy and I left to the mechanic but the alpha's are a relatively simple job and I used to do mine annually.

I always felt it was a regular maintenance item to pull the drive and inspect inside. Preventing problems or catching them early on is the key to enjoyable boating.

-Kevin

 

[Searayguy185]

Thank you everyone who responded. Do you think if i grease it, and it goes away that I'm in the clear?

 

[Bt Doctur]

How difficult is it to remove the drive and inspect it ? They usually go bad from water in the bellow so if its in the U joints and they explode you`ll have bigger problems

 

[Searayguy185]

I pumped about 5-6 squirts of Quicksilver grease in the gimbal zerk today and it seemed to quite it up really good. I can barely hear anything. The average person wouldn't notice it. Looks like it just needed a few pumps.

 

[Bt Doctur]

Yep, let us know when the "Big Bang" happens

 

[scoflaw]

noise=wear....it's damaged

 

[BillK2632]

So had it just not been greased in a long time - ie several years, or do you have water getting into the bellows and washing the grease out of the bearing. You may be fine and all you needed was grease - it could continue to last a long time. If you have water leaking into the bellows, that needs to be addressed now. Only way to know is to pull the drive and inspect. If boat is on a trailer it is an easy task. All you need is some hand tools and a new gasket set. If it were me and it was not convenient to pull the drive now, I would monitor it, and plan to pull the drive end of season and address it then. I say this assuming boat is on a trailer or lift, if not and it is moored, you need to verify there is no leak in the bellows ASAP.

 

[Searayguy185]

I guess since I've never pulled it, I'm a little nervous doing so. Again I've only heard the noise in the forward drive gear. Not reverse or neutral at the same Rpm. Could it be just the noise a prop makes?

 

[BillK2632]

Pulling the outdrive is easy, but a little daunting the first time. Google it, there are lots of articles and youtube videos. If you plan to do this - which you should, or have it done. Build yourself a stand for the drive, makes things much easier. I pull my drive every year and inspect things, every 3rd year I replace the water pump (in the outdrive on the Alpha I). It's a one person job on an Alpha I.

As far as the noise only in FWD, could be. Outdrives make some noise and the harmonics change at different RPMs, plus you have engine noise, vibrations through the hull and water/wake noise, it's hard to diagnose a problem just from sound. Typically however, a failing gimbal bearing makes a growl in F-N-R as the input shaft spins all the time. Noise when turning side to side is typically U-Joints, but again some change in the sound harmonics is normal. Lot's of stuff moving and turning on an outdrive.

The other thing you should consider greasing, since it seems the gimbal bearing was dry, is the input shaft. Typically you just grease up the shaft with the drive off, but most Mercruisers also have a grease fitting on the inside, back of motor near the coupler where the input shaft goes in. Would be a good idea to give that a few shots of grease also.

Like I said if it were mine I would probably just monitor it at this point and pull the drive in the fall, unless of course the symptoms come back and get worse. Or if you start seeing oily water leaking in the boat, sure sign the bellows are leaking.