We have a 2006 340 SDA and have...

[On_A_Whim]

We have a 2006 340 SDA and have a shaft seal leaking profusely when under power. Has anyone changed their shaft seal only?  

[wingless]

Welcome to the forum.

Assumption is the inquiry is for retiring the active seal and putting the existing backup seal into the seal carrier.

The big issue on the 340DA is access.

https://images.boattrader.com/resize/1/41/69/404169_20210907095401419_11_LARGE.jpg

Work on my shafts and seal carriers was done several times by me on my 380DA. The 340DA has excellent access, no disassembly required.

It looks like the best way to gain access on the 340DA is to remove both inboard (above keel) exhausts, the hoses, elbows, risers and manifolds. Removal of those parts would permit a human body to get underneath the engines to perform that work.

My very strong suggestion is to yank the boat and do this work on the hard. It is theoretically possible to do this while floating, but my strong suspicion is that there will be massive water intrusion once the old seal is yanked.

Note that prior to yanking the boat, two tests are required. One verifies the pressurized water flow supplied by the engines to the seal, the other verifies that unfettered raw water ingress exists backwards through the seal. Verify per the seal manufacturer's specs. These are good to perform annually.

If either very important test fails then locate / correct the problem.

I always mark the location of the seal carrier on the hull tube so that I can place it at a different spot each time I service the seal. This puts the new seal to ride at a different spot on the shaft.

Assuming those seal tests are good, my preference would be to yank the shafts (do both even though only one is problematic) using a seal protector so the keyway slot doesn't kill the seal. Swap the existing spare seals to retire the existing active seals and install new spare seals.

Every time I yank my shafts I polish them prior to replacement. I put these across step ladder rungs and take long narrow strips of emery paper for long random motions to remove any crud and blemishes.

My boat has long since had both props, shafts and couplers cross lapped so that disassembly is "easy". When I got the boat both the shafts showed diagonal contact marks on the props and on the couplers and disassembly was a royal butt pain. I have since used coarse to fine lapping compound on these tapered connections to now have 100% contact patch and normal disassembly.

https://live.staticflickr.com/4654/40507538381_b0a121e3d3_c.jpg

https://live.staticflickr.com/4648/40507538291_b2ee90f6bb_c.jpg

https://live.staticflickr.com/4675/40465168122_4aaf8dffd9_c.jpg

Note that engine alignment is very important for decreased vibration and minimized seal wear. My alignment was tweaked by me from normal misalignment to dead-on balls accurate.

The cutlass bearings are also an important part of this system and should be checked for possible replacement.

[wingless]

Here is the Tides seal protector, used when removing / replacing seals and shafts.

https://live.staticflickr.com/65535/50029500446_79694b4984_z.jpg

[wingless]

Prior typo, old: "The 340DA has excellent access", updated: "The 380DA has excellent access"

[On_A_Whim]

Thank you so much!!

[wingless]

Note that a failing seal can suddenly toggle to a failed seal without warning, requiring immediate emergency action.

Do not operate the boat w/ a failing shaft seal.

Schedule the boat for removal onto land for service at the earliest opportunity. (Remember the two floating seal checks prior to yanking the boat.)

[On_A_Whim]

Thanks that’s why we’re having the boat hauled and not taking her to our marina.

[ernie2]

I have a 2006 340 as well. 2017 was started to get a slow leak from the shaft seals too. We thought about using the backup seals but opted to replace with PYI dripless shaft seals. I was told the shaft seals have about a 10 year service life so it was time. I'd bet the cost between servicing the now 16 year old seals and replacing with new is about the same. A little more but the labor is similar.

Since 2017.. we haven't had any problems with the seals. Boat is in salt water full time in San Diego.

Good luck. We love our 340

[Tradition]

We have the same boat. One side went bad, so I ordered both. They changed the bad one, but cannot get the starboard one off, they say it is seized and they would have to cut the shaft. No issues yet, but I am wondering if this happened to anyone else and if there are ways to get it off.

[wingless]

@Mark Lombardo, my speculation is that the "cannot get the starboard one off" is referring to disassembly of the transmission coupler, not removal of the shaft seal.

My prior reply shows that the original part assembly had diagonal contact patches on the taper, hurting the disassembly, corrected by my lapping compound usage.

A coupler removal tool, possibly combined w/ safe rapid temperature change are good steps for disassembly, if required.

My prior replies also include the usage of a seal protector for shaft removal.

[Therapy_on_the_]

Hello,
I have a 2008 340 SDA and if the shaft seals are the dripless.
There is a spare seal on the shaft but I chose to move the shaft seal forward about 1/4" and this stopped the leak. You have to be a pretty small guy to get in between the engines.