Cracked lower unit Yamaha 350

[rfisher]

Cracked lower unit, Has anyone had this happen to Yamaha F350's. Trying to figure out cause and not repeat. Thks

 

[seasick]

First thought is impact damage but it would take a lot of force to crack that housing? Was the prop shaft bent?
Second thought is water freezing and cracking the housing.
Third thought is that something got jammed in the bearing carrier and pushed out the sides of the casting.

If you turn the shaft, does it do so easily without grinding?

 

[Coastboater]

First thought for me was motors were trimmed up during winter, water collects then freezes.
Any prop damage?

 

[Late Again Grady]

Had the same thing happen on a '94 Yammy 200 about six years ago. Same location too.

Hate it for ya. Couldn't repair so had to replace the lower unit.

 

[DennisG01]

If the motor was tilted way up for the Winter, freeze/crack is certainly a possibility.

Or, it could just be a freak thing.

 

[Mustang65fbk]

I’m definitely thinking a freezing thing. My parents did the same thing when we were kids by leaving the outboard tilted up, got water inside and noticed the crack the next spring. Lesson learned, always leave your outboard tilted all the way down over the winter.

 

[seasick]

In the back of my mind I remember something about lower units that were breaking and the fix (if you can call it that) was to reengineer a new version of the LU with a wider diameter carrier bearing housing. Does anyone remember that and if so was it specific to large HP Yamis? Maybe I just imagined that story

 

[wspitler]

Where does the crack emanate from on the forward end. Sometimes there can be a flaw in the casting or a nick or gouge that can create a stress riser in the casting, and then a fatigue failure occurs as the crack progresses. If in fact, it was a casting flaw, depending on the year you may be able to get Yamaha to cover it. If you think it might be from freezing, expensive lesson learned. If there is no internal gear damage and no metallic contamination on the drain plug, then short of physical damage, or freezing damage, the most common cause would be a flaw in the casting.

 

[Sardinia306Canyon]

You may pull the prop and check the LU end cap where the shaft comes out.
There may be substantial corrosion what expands and can crack the housing.
Chris