Adhesive Question re Saildrive Gasket

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mdidriksen
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Adhesive Question re Saildrive Gasket

Post by mdidriksen »

Last winter I had a new engine installed in my S&S 34. We converted to a Yanmar saildrive, and when the saildrive was installed the gasket around the saildrive leg was not adhered properly to the hull. Supposedly this was done with 3M 5200, although based on its reputation it does make me wonder if that was really the case. In any event, the gasket failed (it isn't a watertight gasket -- more just a fairing piece) and it is on my to-do list this spring to fix it. Here is a picture:

Image

So I thought I would show off my ignorance and ask a few questions.

Yanmar recommends using 3M 5200 to adhere this gasket to the hull. While the rubber seems quite substantial, I am concerned about using 5200 due to its relatively permanent adhesion. Are there any alternatives that would be appropriate? Or should I just stick with the 5200 and make sure that the gasket is properly pressured/clamped when the adhesive is applied (I suspect improper clamping was the original problem).

Also, what do I need to do in order to get a good bonding surface, assuming that there is a layer of 5200 already bonded to the hull, but not the gasket. The off-white stuff in the picture is adhesive, not fiberglass. Does this need to be ground off completely? Or can it be roughed up and new adhesive be applied over it?

Thanks in advance!
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Tim
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Re: Adhesive Question re Saildrive Gasket

Post by Tim »

Your best bet is probably to follow Yanmar's recommendations and use 5200 for this seal. I don't know the details of a sail drive installation, but it appears that the rubber relies on an adhesive to secure it to the hull--hence the need for an adhesive sealant like 5200.

You should remove all the old adhesive sealant before proceeding. I wouldn't risk trying to adhere to existing material, particularly given that the bond has already failed at least in part.

I suppose you could use something like 4200, but in my experience, frankly it's not much easier to remove 4200 than 5200, so there's little to gain by using anything but what the manufacturer recommends.

You'll probably never know the exact failure mechanism, but it likely featured user error in one way or another, whether in improper surface preparation, improper clamping/securing during curing, or even using the wrong product.
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Case
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Re: Adhesive Question re Saildrive Gasket

Post by Case »

I just wanted to mention one thing: I think that gasket is supposed to be inside the hull, not the outside. I've never seen a gasket outside. I only realized this just a moment ago.

I recall from other forums that people replace the gasket by lifting the saildrive out inside the boat then installing the gasket in place then lower the saildrive back into the hole.

This gasket definitely looks like it was wrongly installed in the first place since I can see the adhesive areas that it was installed outside the hull.

- Case
Quetzalsailor
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Re: Adhesive Question re Saildrive Gasket

Post by Quetzalsailor »

Now, I'm both curious and not a little bored at work.

When all else fails, read the instructions: http://www.saildrive.us/docs/Saildrive_ ... ctions.pdf

Clearly, this unit is not like the one generating the question, unless the gasket in question is simply a fairing.

I can't quite imagine an installation like the one generating the question unless there's a retaining ring that compresses the gasket in place against its sealant.
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Tim
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Re: Adhesive Question re Saildrive Gasket

Post by Tim »

Case wrote:\I think that gasket is supposed to be inside the hull, not the outside.
The whole thing makes a lot more sense if the gasket's inside, doesn't it.

Check the Yanmar instructions and go from there.
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mdidriksen
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Re: Adhesive Question re Saildrive Gasket

Post by mdidriksen »

This gasket on the SD20 is purely for fairing purposes and it goes on the outside of the hull. You got me nervous with the question (I certainly did not want to have to pull the leg out to fix this) and Yanmar tech support has confirmed to me that the gasket definitely goes outside. (Whew!)
Case
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Re: Adhesive Question re Saildrive Gasket

Post by Case »

Ah, interesting. All saildrives I have seen doesn't have a gasket outside. The hull hole is very tight on the saildrive on all units I have seen so no need for a fairing gasket (as far I can tell). Glad to hear its only a fairing gasket, not the interior type. The interior type requires the pulling of the saildrive. It only happens about once per 20 years or so according to my research so its not that onerous over the long run.

Sorry for scaring you. I really have never seen a fairing gasket outside on a saildrive...

- Case
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