Are the lower seals on saildrives needed?

[akprb]

In my experience with this specific issue the inner seals won't be affected to any significant degree.

That being said the main seal does need to be replaced every 3 to 5 years. Not a big deal to do. (I did every 5)

Had a long talk with a Yanmar tech in NZ about this, his reply "rip em off mate, pain in the arse"

[sapient sue]

CruiserAD

We have had a saildrive in our hull since we purchased the boat in 1996. We have never had a seal fall off in all that time. When we replaced the engine and a new drive was installed, a seal ripped off within a few days - obviously a glue problem and the yard repaired it immediately. If you want streamlined water flow the seals are essential - all sail drives have them no matter what brand - so obviously inclusive in the design. If you proceed with the purchase - replace the seals. Cheers Sue

[wkstar]

This is one of those things where I say-
Very smart people went to school & they would Not have put a lower seal there if they felt it was not needed.
Since I did not goto school for this, I am going to believe that having lower seals is Highly Recommended Activity

[seaclone]

yes my inner seal tore apart after 12 years while in the water but the outer seal held i was able to replace the seal but had to haul the boat out to do so the engine was a 2GM-20 now have the 1D-30 volvos in newer cat and no problems after 7 years i dont plan to change the inner seals unless they fail

[yardie]

They aren't seals. They are called fairings. And on saildrives it's called a boot. There are just there to ensure continuous hydrodynamic flow. The same way a motorcycle fairing flows air around the body and through the cooler.

You can ride without the motorcycle fairing and you can sail without the boot. We replaced ours when we serviced the saildrives. At the next haulout they were gone, again.

[rabbi]

Originally Posted by seaclone

yes my inner seal tore apart after 12 years while in the water but the outer seal held i was able to replace the seal but had to haul the boat out to do so the engine was a 2GM-20 now have the 1D-30 volvos in newer cat and no problems after 7 years i dont plan to change the inner seals unless they fail

The "seal" the OP asked about is the lower boot seal. This one is not a seal and not watertight, its a fairing to reduce turbulence and drag.

The upper seal is what keeps the sea out of the boat. This one can be a single seal (Volvo Penta) or double seals (Yanmar, which also have a water intrusion sensor between the inner and the outer seal).

You write the inner seal of your Yanmars failed. OK, but what exactly has the lower boot seal / fairing to do with the inner half of the upper seal failing?

One more thing: Your new boat with VP engines has a single seal. If it fails, you have some water to deal with.