Knocking noise on full lock

[Mattwalker]

Hi all,

I hope you can help.

When I turn my wheel to full lock (left or right) I get a knocking noise from the propellor.

Its not apparent in a straight line.

Any ideas and on what it might be please?

Boat is a 1998 Sundancer 240 with 6litre sterndrive and bravo 3.

 

[rcon]

How loud? From the props or the drives?

First thoughts are universal joints or gimbal bearing (from drive)

No idea from actual propellor

 

[Mattwalker]

Sorry rcon, sound like the drives (still learning the lingo)

It knocks quite loud on full hard lock and gradually quieter as you release back to straight.

A mate thought unis too ... Are these expensive?

 

[rcon]

HA, I'm new at this too

It's not so much part but the labor.

Try this site (the page I've linked to isn't the right one, but great site and you'll find it soon) http://www.sterndrives.com/replace_bravo_bellows.html for an idea of the labor involved

 

[Larry]

This is a classic universal knock, the universal can go bad from just wear or from water intrusion caused by a leaking bellows. Remove the drive and inspect.

 

[rcon]

I know a dodgy gimbal bearing can cause your drive to spin your engine out of balance and result in damage, can a bad u-joint do similar?

I've got a very slight knock at low speeds, thought might be gimbal, had mechanic listen and he said u-joint and to just let it be (for now). Also said not to use much power when at full lock unless really needed either

 

[Lazy Daze]

Does this happen only at high trim (tilt) angles, or does it happen with the drive "level", as well? It does sound like the universal, though. Can't really comment on "how loud is too loud" over a forum, but the best I can say is that the most you should ever really hear (assuming normal/low trim angles) is a muted or faint sounding knocking.

What model year are the engine and drive?

 

[rcon]

In error

 

[Mattwalker]

Ok ... So the boat is at the mechanics for the last 7 days and I went in today to see what was happening only to be told the bad news

the uni has been replaced as has the gimble ... The knock is still there.

it doesn't matter what angle the trim is at the knock is till there.

if I had to describe the noise level I would say it is like a knock at the front door.

the engine is brand new fitted this year direct from the USA and th drive I am unsure....

Any other thoughts? Could it be the gearbox?

 

[rcon]

Oh wow, front door knock is well outside the range of my knocking.

Good luck chasing this one down

 

[DustinL]

Sounds like you may have a coupler fixing to let go on you.

 

[Mattwalker]

Apparently it is a gearbox ... Changed the oil and told should be ok.

whats the worst that could happen?

 

[Lazy Daze]

It's hard to say what effects, if any, this has had. Obviously, worst case in a new drive or possibly just a lower/gears.

What type of fluid was in there? Was it the Merc Hi-Perf stuff (bluish/green)?