2006 Volvo out drive thumping

S

soulhawaii

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I have a 06 chaparral boat with a 5.7l Volvo, dual prop outdrive. First time with a Volvo, and pretty novice with boats. All was good until recently, when I start the boat, there is what best I can describe a thump every second or so, coming from near the top of the outdrive, possibly where the transom is.

I did previously keep the drive in the up position while near shallow water, and in neutral for 20-30 min. Just read that it's bad for it? Before pulling it, since I have very limited space, does this sound like u joints? How can I better tests it? And how big of a job would it be? Appreciate any insight before I dig into this.
 
Scott Danforth

Scott Danforth

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yes, its really bad to have the motor running with the drive up.

with this being a new to you boat, you should have pulled the drive, inspected the u-joints and gimbal bearing, checked alignment and replaced the bellows long before you ever put it in the water.

pulling the drive is part of annual maintenance
 
tpenfield

tpenfield

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Gimbal bearing or U-Joints. Either way the drive has to come off.
A mechanics stethoscope may give you a better indication of the source of the 'thumping'. Have you driven the boat at cruising speed with this issue? is it better or worse?

Are you planning on fixing this yourself?
 
Lou C

Lou C

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When in shallow water, the highest I ever have mine is about 1/2 way up, I marked this position on the trim gauge so I know it's up but not too far up in shallows. All the way up is only for idle and only for brief periods.
I'd try to narrow down the sound with a mechanic's stethoscope and then check the likely causes, u joints, most likely....
 
C

cyclops222

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DO NOT go into shallow waters. Buy a boating map that shows depth and what the bottom is made of.
Only way to prevent damage like yours
 
D

Donald0039

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I do not think running with the drive up and a thump are connected.

Running in shallow water can cause the outdrive to suck up muck or mud and if the props hit something it can damage the props and/or the outdrive. That can get expensive.

Pulling the outdrive is not a huge deal but a duoprop outdrive is heavy. They sell stands you can use to help get the drive off and the hold it once off.

Greasing and checking the u-joints yearly is good maint. Max would be every 2 years.
.Check and grease gimbal.

If it's not the u-joints or gimbal then drain the gear oil looking for metal chunks.
 
tpenfield

tpenfield

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I know the Bravo drives are ok in shallow waters at idle speed. Maybe others not so much.
 
Scott Danforth

Scott Danforth

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guys, read the OP-s first post. he ran the motor drive full-up for 20-30 minutes at a time.

we are not talking a 20 second blip to navigate a bit of shallow water, we are talking over 200,000 cycles at a time of the u-joints making that greater than 8 degree bend on the double cardan joint.

that will take out any u-joint. dont care if its volvo, mercruiser, etc.. u-joints do not like more than 4 degree angle per joint. that is 8 degrees on the double cardan joint which is where the trim limit is also set on these drives. running full up, that is 45 degrees. my guess is the shaft is now hitting the housing

the duo-prop drive is a bit over 100#. can be done by one person, however easier with two. much lighter with the props off
 
C

cyclops222

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Excellent description of how to....DESTROY..... any universal joint.
Thank you Scott. (y)(y)(y)(y)

To me the biggest reason ....NOT TO BUY...... a inboard sterndrive boat. Is those universal joints.
 
K

kd4pbs

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I've often seen people write that trimming a drive up while idling/running the engine on a sterndrive will kill u-joints in a hurry, and personally I don't do this, but I'd love for someone to explain the difference between trimming a drive up while steering is centered and having the drive down while steering is turned full port or starboard. I never see anyone warn others about this, but for sure, that set of u-joints will be cycled just as drastically whether trimmed up 45 degrees from full down or steered 45 degrees from straight ahead.
That being written, a thump every second would tell me there's a gimbal bearing issue more than a u-joint issue simply because the u-joint would cycle every engine revolution versus a roller or ball in a bearing rolling itself around between the races and making noise against some part of the bearing each time it passes.
 
C

cyclops222

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Get a outboard motor if you want to trim the drive up. When in shallow water. They do not have those troublesome U Joints. My Mercruiser 2002 never had a inspection or problem with drive joints
 
Lou C

Lou C

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I have often wondered why sterndrives didn’t use CV joints instead of double cardan joints….
 
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