Silicone to replace power head base gasket?

[adam1961]

Does anyone use some kind of silicone or RTV in place of the base gaskets on Classic OMC motors? I find myself going through many gaskets on the motor that I run on my racing runabout. It seems I am always pulling the power head for one reason or another. Is it possible to use a sealant, or should I just keep replacing the gaskets( one on each side of the stainless baffle) ?

Adam

[fleetwin]

Adam, I would not try to substitute RTV/sealer for base gaskets. You could try just coating the new gasket on both sides with grease so the powerhead will come off without damaging the gasket during future repairs.

[drifter]

On a similar note, I have a repair manual that shows a head gasket (on a 57 Johnson 10hp) being replaced with anti-seize compound covering both sides of the gasket. I never tried it but wondered why they did this. Is this a normal repair practice?

[fleetwin]

Drifter, would love to know what kind of manual would make a recommendation like that….Some of that anti-seize stuff can actually promote corrosion when mixed with the aluminum and salt water. Yes, I realize that the anti seize company does make aluminum compatible products, but they would have little value when it comes to sealing a head gasket.
The best stuff to use when sealing head gaskets is the OMC/Merc gasket sealing compound. Using the gasket sealer around the outer edges of the head gasket is all that is needed, this will not help seal a fault in the cylinder to head surfaces, although it surely won’t hurt to apply there as well.

[Mumbles]

Aluminum paint used to be the sealer of choice for automotive copper composition head gaskets! ☺

[Tubs]

Adam1961
Sent you a PM.

A "Boathouse Repair" is one that done without having tools or the skills to do it properly.

[drifter]

Well, I was almost correct. The manual is a book titled "The Classic Outboard Motor Handbook". Page 91 shows a photo of a man brushing anti-sieze on a 1958 Johnson 10hp on the block where the head gasket mates to the block. The photo caption reads:" A gasket sealing lubricant is applied to the water jacket and cylinder assembly surfaces".
I always thought this was weird.
Drifter

[amuller]

quote fleetwin:

Drifter, would love to know what kind of manual would make a recommendation like that….Some of that anti-seize stuff can actually promote corrosion when mixed with the aluminum and salt water. Yes, I realize that the anti seize company does make aluminum compatible products, but they would have little value when it comes to sealing a head gasket.
The best stuff to use when sealing head gaskets is the OMC/Merc gasket sealing compound. Using the gasket sealer around the outer edges of the head gasket is all that is needed, this will not help seal a fault in the cylinder to head surfaces, although it surely won’t hurt to apply there as well.

I’ve wondered if the copper loaded anti-seize is really OK to use with aluminum. Is that what we are talking about here?

[PugetSoundBoater]

You do not want to use anti sieze with copper on Aluminum in it due to the galvanic corrosion/dissimilar metals issue. I use Jet Lube Marine Grade Non Metallic Anti sieze.Fastenal stocks it. Locktite makes one also.

"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson

[collectorinspector]

I do not believe that silicon or RTV squeeze of any type should ever be used……….

Plenty of old school gasket/sealant/preparation with some attention to detail before assembly is the ONLY thing required.

Just saying.

BnC

[Author]

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