How to seal through transom exhaust?
 

G'day all,

1 quick question for the floor:

How do I seal / prepare the holes for a through transom (dry) exhaust?

I have the exterior seals & rings on order but what's the best way to actually prepare the holes in the transom that the pipes go through?
I've currently got 4.5" holes for the 4.5"OD pipes that fit through.

My curiosity is that when the exhaust gets hot it will expand inside the transom. I don't want to cause any other issues so should I make the holes a couple of mm bigger than the OD of the pipes to allow for expansion? And how should I then seal the holes? Sealant or epoxy or should I glass the inside of the holes?

The pic below is the holes at 4" before I enlarged them to fit the dry tails.

Any tips or advice would be greatly appreciated, thanks! :drink:

Seal them with a couple coats of epoxy. A penetrating epoxy would be best, but anything such as West Systems will be fine.

As long as its not true dry exhaust and just thru hull exhaust you don't need to worry about it expanding. I've never had a problem, and the ones I've done are a fairly tight fit.

It is a true dry exhaust (water doesn't mix with exhaust) but it is water jacketed if that's what you mean? (As opposed to no water at all.) The water exits at the tips of the tails. The holes are snug now (no play or room to move) and they line up perfectly with the exhaust (Pure LUCK!) but I'll have to expand them a little bit so I can coat with epoxy.

Is this all I need to do?

Thanks for the help. I was dreading something more complex required! :drink:

Fixx
 

your going to need thease to..
http://www.eddiemarine.com/store/car...l&p=11434&c=58

make sure you tell them 5'',check with cmi or stainless marine also if eddie wont make them..I also put a bead of sealer around the inside of the transom to keep the water out..you will need some expansion room and the pipes cant rub on the transom,they heed to flex a bit so you dont crack the weld son the headers of the tails..also it your to tight you will hear and feel motor vibrations through the hull so make sure the pipes go through loosely.

If I see this correct you are making the holes the exact same size as the tails, 4.5".
I would recommend that the hole in the transom has at LEAST a 1/8" if not a 1/4" gap between the tail pipe and transom all the way around. Any flexing of the boat or torquing of the engine will put stress on the flange where the tails bolts to the manifolds and result in cracking in that area. Something has to give if those pipes can't move a little in the hole. You may have to adjust the engine sometime to align the coupler and end up putting the exhaust in a bind. I would seal the open grain in the holes with some fiberglass resin. Then the way I do mine is I fill the area between the outside trim ring and the tail with black silicon and smooth it out. It's then totally sealed and yet the tails can move some in the holes.

That sounds good. I've got the transom seals on order through Brad at CP Perf, that and new rope seals, gaskets etc.

The room to move was basically what I wanted to know. I'll stretch the holes out another 1/8" - 1/4" all the way round now that I know how far to go, thanks!

I'm going to grab some of that penetrating epoxy if I can find it and seal the holes up. When I mount it all up permenantly, I'll silicone the gap inside the seal ring before I slip the gasket over and clamp it down with the rings.

Would the movement of the tails cause any risk of damang the welds on the headers? On my old Sanger with OT pipes, I had to make up some brackets to support the exhaust because I was told the movement of the tails (mufflers) would potentially crack the pipes welds or even the heads at the bolt holes.

I would assume the movement (1/8-1/4") wouldn't be enough to worry about though, is that correct?

Thanks again for all the help and advice!

If the tails do bind against the transom at some point it's going to cause a crack or break at the weakest place whether it be the tail flanges or the header welds.

Fixx
 

Did you read or do you just post?? also you failed to mention to put some oil on the pipes so he can remove them...

mr fixall, I happened to have been making up my post while you had entered yours. I certainly wouldn't sit here and repeat what another had already posted intentionally if that's what your getting at. It happens all the time on these forums.
I'm here to help those with question on problems I've experienced before, not to act like I'm the only one that knows anything by just posting and not reading.

As far as oil on the pipes I've never done that. A little twist of the tail and the silicon breaks right loose.