Deisel Heater Skin Fitting Temperature.

[Yellow Ballad]

I'm just planning my install for a chinese diesel heater.

I plan on fitting the skin fitting on the underside of the overhang of the transom (same location as the engine exhaust but on the opposite side of the hull, probably 20cm above the waterline). As the boat sails it squats meaning it will get wet/semi submerged with the tail wave (?), obviously not a problem as the heater won't be used underway but I would like to make sure the skin fitting is sealed against the hull so not to allow water past. Before I start drilling holes (or buying the fitting) can I ask opinions of those that have a heater.

I understand the design on these fittings are so they don't transfer heat to the hull butI imagine some heat is, would a sikaflex product take whatever heat that is transfered?

If not would a high temperature silicone sealant like JB welds Red RTV be ok to seal a through hull?

I could put a skin fitting on the transom itself however it won't be as aesthetically pleasing not as practical for the exhaust run but I would rather not, especially as I don't want a hot gas pointed directly towards my windvane.

Thoughts?

 

[PaulRainbow]

CT1 works fine, or Screwfix OB1. The fitting doesn't get that hot anyway.

 

[PetiteFleur]

I don't think putting the skin fitting under the overhang is a good idea - if water gets up the exhaust as it squats it will fill up with sea water and then could reach the heater itself - not a good idea + could ultimately let water into the boat. Sea water in the stainless Steel exhaust will probably corrode it. I doubt the heat when it reaches the wind vane would damage it.
Also get the angled exhaust so you have to put a bend up then down to the exhaust fitting.

 

[pyrojames]

Make sure that if it dips/gets wet it doesn't drain back down the exhaust and flood the heater. I had similar concerns about my skin fitting on timber, but the design means it does get that hot. Not sign of heat in the timber of blistering for the paint around it either. Pretty much any decent silicon bases sealant should keep the fitting tight.

 

[prv]

Another note of concern about allowing water into the exhaust. A nice high loop should keep it out of the heater (though you only have a limited length to play with if there’s a silencer in the run, which definitely needs water kept out of it) but the difference from an engine exhaust is that this pipe is metal rather than rubber. Nominally stainless, but quite thin and full of little crevices due to the flexible construction.

Pete

 

[Yellow Ballad]

I plan on fitting a swan neck / loop which would be 24" tallish if I fitted the skin fitting facing downwards on the overhang. The heater exhaust outlet would be about midway below the top of the loop with a condensation drain. Like I say I could go through the transom but if I can avoid it I would like to.

I was hoping to use this type of fitting which looks to me like it would be 6-8 inches long, if I have issues I suppose the pipe could be extended. I would imagine the pipe would be pretty much vertical once through the hull.



Silencer I was thinking about having in the drop near the top but it's all down to space.

 

[PaulRainbow]

I plan on fitting a swan neck / loop which would be 24" tallish if I fitted the skin fitting facing downwards on the overhang. The heater exhaust outlet would be about midway below the top of the loop with a condensation drain. Like I say I could go through the transom but if I can avoid it I would like to.

I was hoping to use this type of fitting which looks to me like it would be 6-8 inches long, if I have issues I suppose the pipe could be extended. I would imagine the pipe would be pretty much vertical once through the hull.

View attachment 122610

Silencer I was thinking about having in the drop near the top but it's all down to space.

View attachment 122611

Not keen on that location Tom. If the stern drops into a trough it looks like water would be forced up the pipe, i'd fit it in the transom and still fit the swan neck.

 

[pvb]

Not keen on that location Tom. If the stern drops into a trough it looks like water would be forced up the pipe, i'd fit it in the transom and still fit the swan neck.

I'd agree. The proposed location is too close to sea level, contrary to most manufacturers' recommendations.

 

[Yellow Ballad]

I thought people would say that (both water being forced in and lower than recommended) ... and I suppose I came here knowing I need to do it differently. My hoping that the engine exhaust not having any issues in the past would give me half a chance.

I have to admit the exhaust is the bit I was not looking forward to work out.

I think I need to get down to the boat, crawl into the locker and see what's going to work on the boat. Being a reverse stern my only concern was the angle of a lot of these fitting would out the connection tube near horizontal.

 

[Ammonite]

You need something along these lines. It just needs to be slightly above horizontal so water doesn't pool in it with as high a swan neck as you can manage. You should also throw away the Chinese exhaust and buy a better quality one and associated fittings.
Google Image Result for https://www.butlertechnik.com/images/24mm-exhaust-hull-skin-fitting-for-eberspacher-or-webasto-marine-heaters-p1710-1713_zoom.jpg