bedding mercury filler blocks??

[vislaguy]

I have seen filler blocks bedded, and water cooled, many different ways. Is it better to circulate water just through the filler block, or to circulate water through the exhaust cavity surrounding the filler block? Also, what is the best way to bed the filler block to the engine; epoxy, high temp. silicone, or bondo? The filler block that I have is cut loose to the engine, so that may be a deciding factor on which way to go.

Thanks,

Mike

[sam]

High temp silicone works for me. None of my filler blocks are water cooled.

[alky6]

We cool the filler block by machining grooves (then capping of course) then use two 1/8" NPT nipples (one in and one out). After careful cleaning of the surfaces we use high temp silicone. Don't recomend cooling around the filler block as a potential leak can fill a cylinder with water.

-paul

[David_L6]

O'Brien's method is the neatest set up I've seen for a water cooled filler block. Other than that what alky6 described is a good set up. I use silicone to glue in filler blocks.

[Bill Huson]

never fooled with filler blocks . . .

but I agree with the many votes for high temp silicone. Methinks heat and vibration would destroy epoxys, and Bondo wouldn't last ten seconds. Silicones kick butt. On my old Dakota Mopar didn't use an exhaust manifold gasket but used a thin coat of hi-temp silicone.

[jeff55v]

also...

Remember, when the Merc block heats up it will expand outward. If your filler block has no clearance, and your sealant has no give, the cylinder wall will be forced to warp.
Another reason to use hi-temp silicon.

[crankbearing]

Bondo

I use bondo when I seal them as does Brinkman in his book, I just rebuilt a mod that I put bondo in and it took 10 minutes to dig the filler block out. The only real way to get a proper seal is too weld the thing in my opinion, I think that silicone is a temporary fix. They all come apart with vibration. You can tell anytime you pull the filler block out, you can always see leak areas on any off the sealing methods you try. If you do it right and leave the filler block below the deck line a little bit that seal it all up right away as to push out the excess sealer when the plate is bolted down you will have no problem with the warpage factor.

I had always wanted to come up with a solution but it would just not be cost effective. If you look at a Merc 4 cyl 85HP or bigger in-lines, they have water passages in the exhaust side that a machined flat and a plate is bolted in with a gasket seal between the block and the inner exhaust baffle plate. This is the best solution but you would have to weld tracks into the block and them have that machined flat and tap and thread the holes to bolt the filler block in. very time consuming and costly.

Regards,

[elda nichols]

filler blocks

Mike, I Put Marine Tex On Mine And Circulate Water Through And Around My Filler Block..marine-tex Is Costly But I Did Not Have Any Luck With Silicone ........if You Cool It Enough I Don't Think Warpage Is Going To Be A Problem ...water Goes To My Exhaust Side First........

[sam]

I've never had any trouble with silicone, maybe I'm lucky with the fit of my filler blocks. Some of them came in motors that were bedded with MarineTex, some Bondo. None of mine had any evidence of leaking no matter what they were bedded with even though some had apparently never been apart since the 1960's.

[Larry Mac]

I agree with Dave I have never took a filler block apart that didn't show oil under it. I would never run water around the out side of my filler block just because of the leak factor. All my filler block are cooled internal so there isn't much of a chance of a leak. I know people get by with silicone, Bondo, etc but I never had much luck if you run water around the outside of the filler block.
Larry Mac

[Dave M]

Tried all but Bondo

We found a mixture of using epoxies or Marine Tex and Hi Tem Silicone works well for us. Have not had much leaks. Big thing is not getting to much or to little silicone in the right places. If in doubt use Marine Tex, seems to hold up very well. Might take 20 minutes to dig out instead of 10 minutes. Small price to pay to have it sealed, and much cheaper than welding anything in and machining, Dave S is right, for the non performance gain, that just does not seem very doable.

Once you have it in place, you can always run the orange silicone around the edges to be sure of a seal. We have used just Silicone before, it will work, and if you are experimenting with things, makes it easy to take out and replace if you need to while adjusting other things. I would not count on the silicone lasting more than a season if that.