KCHOTBOAT

I am sure you can get the lightings with stainless inner tubes now.

Hardcore

Yep. I definitely need at least stainless inner tubes (or good coating) since all we have down here is salt water. You can get the Lightnings with S/S inner tubes for about $1600.00 or fully Stainless (platinum finish) for about $2500.00.
Teague also has the new CMI Sport Tube Lights (long tube primaries and no tailpipes) for about $2600. These are what I will probably go with if I decide to buy a fully S/S water-jacketed header. They are rated for up to about 750 HP, but I recall reading somewhere that the inner tubes are 1-7/8" I.D.
That provokes a thought - why is it that most race cars (drag and other) as well as dynos seem to need to use larger primary tubes (like 2 1/4" +) to make maximum power on a 1hp+ per cubic inch B.B. Chev. but boats tend to use something smaller with a similar engine? Is it that the cooling effect of the water-jacketed header makes the exhaust gas denser and therefore will not need the larger pipe? (Or is it just that no one except the most serious racer can afford to spend six Grand on a pair of CMI Big tubes or Stellings?)

mcollinstn

Inner tubes are stainless on all Lightnings. The outer tubes are the ones you have a choice on.

There is a definite performance benefit to keeping the outflowing gases as hot as possible. For this reason, it would be worth the trouble and expense on a race boat to have a set of dry longtube CMI tubetops or Stellings thermal coated on the insides of the headers and tailpipes. They would still run water jackets but the outflowing gases would exit the tailpipes MUCH hotter than normal. This will improve exhaust scavenging.

Aside from that, I honestly see no lure in using the thermal coating as a means for ensuring engine bay safety on an inexpensive set of jetboat headers. It will never be legal, if you care about that.

Try a set on a dyno motor. If the external wall of the pipes stays below 300 degrees after extended WOT operation under full load, then I say you're onto something. Over 300 degrees, and you'll never get my blessing.

Hardcore

Cool. That's the kind of answer I was expecting. I don't have access to a dyno and I'm very anxious to get this boat in the water so I think I'll probably just go with the Lightnings with the restricted water injection. This option apparently reduces the amount of cooling water going into the exhaust by dumping most of the water through a couple of 3/4" dumps and only enough water is allowed into the exhaust stream to cool the tail pipes and hoses. Sounds like the best of both worlds to me.
Thanks again for all your input guys.

mcollinstn

The tailpipes are already cool cause they are fully waterjacketed. The water reduction is where the water is introduced at the rearmost portion of the water jacketed tailpipes. As you said, this is to cool the gases so they don't catch your hoses (that go from the taipipes to the tips) on fire. I'd run the blue silicone hoses with reduced water just for longevity (and while the blue hose is expensive, the 4 6"-long pieces don't really cost that much since you only gotta have 2 feet of it ($60 versus $15).

Restricted water only adds $60 to a pair of headers if you order them that way. You do gotta add a dump fitting thru the hull for the excess bypass water though.

puder

ahhh rubebr hoses!!! (you can run tailpips that go through the transom as well. no rubebr to melt (i've done that )

Cord

iTrader: (2)

When you are running the pipes will red hot. This will be worse with the wrap as it will keep the heat in. I've heard of people thermally cooking their headers until they blow out from the fatigue. That's why they run stainless in the race cars.

Mc-I thought the inner tubes on the Lightnings were mild steel, but with a barrier coating.

BTW-the coast guard (and insurance company) would frown on not having a jacketed or injected exhaust.

aTX427

I have a set of CMI straight tails if your interested. They can be run dry or wet and have the mercruiser style flange.