Lower Unit Shakes When Turning

[groberts4]

Hey guys - I've got an '06 262 with an 8.1L Volvo Penta. I've had minor issues with the lower unit for many years, at one point having it completely rebuilt for almost $5K. My issue is that it shakes the whole boat if I turn it more than a half turn in either direction. And if it's tilted up even a little the issue is magnified.
I know you shouldn't turn the wheel if the unit is tilted up, but sometimes that's the only way to get the boat to turn at idle speed. That aside, the unit now shakes during turns - a little at higher speeds, more at idle. I had the props balanced last year and haven't hit anything since, not even a sandbar.
Is this just normal I/O behavior, or should I take it back to the shop?

[jwill323]

Is the drive the XDP Composite drive?

[groberts4]

The lower unit isn't a composite, it's an SX (according to the guy who services it).

[CBO]

Pictures would help.

[Kate]

"I know you shouldn't turn the wheel if the unit is tilted up . . ."

Huh?

If you trim up during cruise, you shouldn't turn the wheel?

[TwoDuckDad]

My experience is that in a moderate to high speed turn with the outdrive trimmed up to cruising speed level, you can experience some cavitation. However, this does not indicate a problem with the mechanics of the boat.

[bruceb58]

Sounds like u-joints are failing. When was the last time the drive was pulled and they were inspected and the drive/engine alignment was checked?

[groberts4]

Thanks for all your responses, I appreciate it. Here are some answers:
1) Best picture I have right now is below;
2) "Shouldn't turn with trim up?!?" - only a problem if it's WAY up, like when I'm at a dead-end canal and have to turn this 28' boat around in 40' of space. Only way I know how to do that is trim it full up, as in the picture below, and then crank the wheel. This makes the boat turn in a much tighter arc. It's very effective. However, that apparently is very bad for the lower unit since all the shafts and gimbals and related parts aren't aligned. Based on the terrible shaking, I'm sure it's not good. However, my problem occurs under far less challenging conditions, like when the engine is trimmed up just a tad and the wheel is turned even 25% in either direction;
3) Cavitation: Yep, that can happen as you described, but that's not this problem;
4) U-bolts: a likely culprit. I've got an appointment to meet my favorite mechanic at his dock and take a spin, get his take on what it needs. Based on my description over the phone, he agrees with you.
I'll pass along whatever I learn.

Lower Unit - Tilted Up.jpg

[jhnmdahl]

The U joint or universal joint looks something like this, and is not a bolt:



It's not actually rocket science to replace, and since you're likely pulling the drive unit to look at it and align it anyway the additional cost to install should be minimal.

John

[Kate]

". . . dead-end canal and have to turn this 28' boat around in 40' of space."

Have you tried the crabbing technique, aka the "pivot turn"? Executed properly, you can easily pivot her 180 degrees in that space.

[iceclimber]

Agree u-joints. Also check power steering but likely not.

[groberts4]

". . . dead-end canal and have to turn this 28' boat around in 40' of space."

Have you tried the crabbing technique, aka the "pivot turn"? Executed properly, you can easily pivot her 180 degrees in that space.

Oh sure, that always works, just takes longer and not as satisfying as reducing that turning radius by 50%. However, given the potential damage to the lower unit, I've been crabbing for awhile and will continue to do so.

[groberts4]

The U joint or universal joint looks something like this, and is not a bolt:



It's not actually rocket science to replace, and since you're likely pulling the drive unit to look at it and align it anyway the additional cost to install should be minimal.

John

Thanks, I agree they're a likely culprit. I'll be suggesting that to my mechanic and I'm sure he'll be taking a look.

[smokymance]

I used to have a random vibration on my Volvo outdrive; it would be random, as in any trim up on the drive when starting the engine, it would have the drive shaking back and fourth, sending the boat into a mini booty shake. It was random and would happen for example at a sand bar or similar place, as thats where you usually restart a boat w the drive up a bit in my scenario . Anyhow, long story short, I had to reseal my drive and one of the things that got replaced was the universal u joint, driveshaft thing. It as never done this random symptom again...is it luck? I dont know, but I doubt the new seals on the drive changed how the drive behaves. Hope this helps.

[Fozzy STI]

I have had the same,u joint replaced and never had the problem
Also when you start your engine always your trim totally down.
I see it daily the engine start with the trim up.
It will damage your u joint.