REV sound when coming off plane (Alpha 1 Gen 2, Mercruiser 4.3L 1993)

[babikov]

I would appreciate people sharing their experience on this issue (I understand it is impossible to diagnose without looking at it and hearing the sound, but may be someone had a similar symptoms before).

I took my boat first time to the lake this year. Started OK on the driveway, OK in water, OK at idle and small speed, jumped out of water just fine and showed enough power and speed, planed perfectly. But when I wanted to stop and reduced acceleration, and the boat started slowing down and immersing back into the "hole", I heard very clearly a loud REV sound. Not from my engine. I first thought that there must be another boat in the vicinity and the sound would come from it (since I was slowing down, while the sound would correspond to someone accelerating). There were no other boats in the vicinity and I realized that the sound came reflected off the pier, so it was a sound from my own outdrive! As I think about it, it may be that I have heard something like this in the fall too, but did not point attention to it...

I had a friend in the boat and he said that this could be a sound of a bad bearing (he is not a boat expert, but has some experience with car mechanics). Well, I start thinking about the bearings.

1. In the fall I pumped new grease into the gimbal bearing as expected. This bearing is probably original. About 5 years ago I had bellows broken (corrugated rubber hose cracked) and replaced, so, this bearing could have some water in at that point, but was well greased seasonally, before and after that. Could that sound come from a bad gimbal bearing at all? Through the bellows? Or through the body of the boat? Does bad gimbal bearing make a REV sound when coming off plane?

2. At about the same time (5 years ago) I had to replace a leaking pinion seal, and also replaced the pinion bearing in the upper part of the outdrive, buying a new one from the dealer and installing it according to all specifications. Could it be that this bearing has to be retightened now, after it worked in?? Could that bearing make this kind of a sound??

3. There must be other bearings in the outdrive. Which once are likely to make this kind of a REV noise when coming off plane??

Thanks for your thoughts or suggestions!

 

[alldodge]

Have not seen this issue. When gimbals have issues its normally a growl.
Have you checked the lube in the drive?

 

[Rick Stephens]

Have you been doing the annual maintenance? Major portion of annual maintenance is to pull the drive and inspect the gimbal (turn it by hand, should be stiff and silky smooth) and inspect grease the u-joints and check to see if there is water in the bellows or shift pocket. The above process only takes half an hour and is worth every minute.

I would expect that u-joints or water in the bellows to make more subtle noises than a failing bearing in the drive.

 

[Bondo]

But when I wanted to stop and reduced acceleration, and the boat started slowing down and immersing back into the "hole", I heard very clearly a loud REV sound. Not from my engine.

Ayuh,..... Due to speeds, 'n conditions, it's My WaGuess, that what you heard was the exhaust bein' uncovered by the prop wash/ back wash,.......

How quickly or leisurely you were slowin' down, plays a major roll in how it would sound,.......

 

[babikov]

Dear experts,

Yes, the gear oil is there. I replaced it in the fall. Just to be sure, I opened the top plug and checked it - perfectly clear and at the right level. In the fall I also greased all zerks, with proper grease.

What I should admit, is that I do not remove the outdrive regularly. One reason is that there is nothing to grease there. My U-joints do not have any zerk in them. I used to spay oil over U-joints but someone told me that it does not help it at all, since it does not penetrate anywhere, but the oil will be forced out by centrifugal force and will cover everything around, and may eventually harm the rubber of bellows. The second reason is that if I remove the outdrive, then I need a set of gaskets to put it back... Finally, I don't use my boat a lot (a short Wisconsin summer)… So, I "reduced" the maintenance to replacing all filters, liquids, and winterizing, without mechanical work...

What I will do for sure this fall, will be to remove the outdrive and check the gimbal. Promise!

The idea of back wash may actually be the right one. I stopped abruptly. By simply returning accelerator to the vertical position. I will try to experiment with this, may be with open engine compartment, and will update you on my findings.

Thanks to everyone!

 

[QBhoy]

Mmm. Is it not just the exhaust going back under water line ? Especially noticeable if your exhaust bellow is burst.

 

[babikov]

I raised the outdrive and checked the bellows. Both are in place, intact...​

 

[babikov]

Dear Alldodge,

Thanks for your response. ​

You mentioned that when the gimbal bearing gets bad, you hear a "grawl". Can you, please, expand on that a bit. Does that belong to the idle speed and/or low speed too? Or only higher RPMs. Only with the outdrive engaged or always? When do we first notice and start suspecting a bad gimbal bearing, or the one that starts failing or is about to start?

I am just thinking that if I try to diagnose it with the muffs, on a driveway, without the outdrive engaged. I can raise RPMs listening to the noises. The gimbal bearing is rotating in this case at a good speed (although without a load). Would I "hear" a bad gimbal bearing in this case?

Unfortunately, the yoke bearings would also be engaged, but the lower part of the outdrive would not. Would this give me at least some idea where a problem could be...

Any recommendations of this sort??

Thanks! ​

 

[Rick Stephens]

If in doubt, take the 10 minutes to pull the outdrive and inspect. It is so easy to do that it is silly to ask what people who aren't there think is wrong, when you can actually look.

 

[alldodge]

Normally won't hear much on muffs until the bearing gets pretty bad. Under load it shows up easier. The drive being turned will amplify it more, or trimming up

As Rick said, remove the drive and reach in with your hand. Place couple fingers inside the bearing and rotate back n forth. It should feel as smooth as silk, if there is any roughness there is an issue

 

[babikov]

Dear forum experts. I removed the outdrive just now (few month after the beginning of this post), to combine this check with annual maintenance. I found no signs of water or anything else suspicious in the bellows - everything is clean and lubed as I put it together about 5-6 years ago... Not bad for a non-expert like myself. There was some grease around the gimbal bearing, pushed out by me greasing it annually. I wiped off the excess grease on the bearing, but it is hard to clean the entire bellows (I heard someone saying that the grease on bellows may damage it -- that does not sound likely to me, correct me if I am wrong).

Coming to the gimbal bearing: I can rotate it but it is hard to tell whether it is "silky smooth" or not. The problem is that I just have nothing to compare with... When I turn it I can feel the "sound", or may be just the motion, of the parts inside the bearing. No rough spots, stops, or slides. But I cant say it is silky smooth, simply because I feel something as I rotate it.

One idea I have is to simply buy new gimbal bearing and compare. If the one in the boat right now is bad (according to that future comparison) then I would replace it sometimes during the winter. If not, I may simply keep new bearing for the future service. My question to you is what is a reasonable manufacturer? Is it true that one has to go with an original MerCruiser, period? Or, there are other reasonable choices??

I checked e-bay, these bearings start from $25-30. Does not seem expensive, but how reliable these parts are? Is there a reliable online store to buy gimbal bearing?
Thanks for your feedback!

 

[alldodge]

Grease in the bellows is of no issue or concern.
Your bearing feels fine then it should be good. My 1995 Rinker still has the original bearing in it

 

[babikov]

Alldodge,

Thanks for your response. I tend to replace the gimbal bearing, because about 6 years ago the previous bellows cracked, and I did not immediately realized that. Fixed later, and there was a period of water passing through the bearing. When I repaired the bellows, I pushed the bad grease out of the bearing by greasing and rotating it over and over, but did not replace. May be this is the time. So, if I am to buy the gimbal bearing, where is a good online store? Manufacturers to choose and to avoid. Is any new bearing good, or the manufacturer matters? Is Sierra good?

 

[alldodge]

Last time I bought gimbal bearnings, I got them from bearing supply in Louisville. One is Link belt and other was Timken. Buying on-line is a crap shoot, so unless your buying Timken, FAG, Link Belt then I would buy Merc or Volvo Penta

I try to stay away from Sierra

 

[babikov]

Thanks! This is truly valuable!