Liquid gasket on gearbox?

[Ifraser]

Hi, I have an old C Kip 40 trawler yacht with twin ford lehman 120hp's through borg warner CR2 gearboxes. I've just re-launched after 2 weeks ashore and after a few cruises have discovered a leaking gasket on the port gearbox. It's the rear gasket to what's called the reduction part of the box. In theory to replace the gasket I would have to draw the shaft out in order to remove the back end of the gearbox to install a new gasket. I think that will be pretty tricky with the boat in the water! However it's been suggested that with today's modern hylamar liquid gaskets it might be feasible to only separate the box by about 1" which would be enough to get a liquid gasket bead in there instead. What are your thoughts and experiences around that? The only other thing I thought was to slice the gasket at the top so it could be inserted with a limited gap. Then maybe apply just a little gasket sealant around the site of the cut. If this cut is at the top of the box I would think it was less prone to failure than at the bottom which is always immersed in the ATF. Any thoughts or advice greatly appreciated. I have a trip to Normandy planned for early July and would very much like to get it done before then. I really want to avoid lifting out if at all possible as I've only just gone in and it will add a huge cost as you can imagine. Thanks in advance. Iain

 

[Ardenfour]

Well, I got Hylomar Blue on my gearbox to engine joint and so far so good. Would seem that gasket and sealant would be the way to go, even with a cut at the top, belt n braces an all that

 

[30boat]

I'd never do that.It's a bodge.It'll be much better if you take everything apart ,clean the mating surfaces and install a new gasket.That'll give you show you why the old one failed too.

 

[VicS]

Cleaning the joint faces is an essential part of fitting a new gasket. You may not be able to do that without fully separating the two parts.

Tried just nipping all the bolts ?

Oyltite may be worth a try at least as a temporary measure . Its not going to suddenly fail catastrophically anyway.

http://www.frost.co.uk/automotive-g...ltite-stik-seals-oil-leaks-thread-sealer.html

 

[NickRobinson]

Silicone gasket is useful if you use one that's happy with ATF.

Sorry to be a bringer of bad news but I don't think an undisturbed gasket has any reason to leak.

More likely its the oil seal throwing oil about?

 

[NorthUp]

Depending on which particular gasket you are replacing, be aware that some of them may be setting
the bearing clearances in the gearbox.
Too thick or thin will affect the life of the bearing drastically if affected.

If you replace a gasket and wish to cut it to allow fitting without full dismantling, make the cut a dovetail joint and use
jointing compound like hylomar as well.

 

[Lakesailor]

Many gasket surfaces are sealed using silicone gasket material these day. Blue Hylomar is not such a material.
As has already been said, some gaskets are part of a preload on bearings, but many others are merely leak sealants.
I have a friend who is a top quality independent mechanic. He prefers silicone gaskets unless there is a specific reason not to use it.