GM Powertrain who supplies the long blocks to Merc, volvo, etc. puts inconel exhaust valves in and super hard seats. Some of the engines get used for industrial power plants and run on propane and natural gas. Maybe some don't have them but all the ones I've seen do. Here's the GM replacement part # 14097049..

And I agree with you, the Bravo will be fine for that application.

sounds like a good winter project for me ! thanks for letting me know about the supercharger .. so you would go with a procharger vs any other supercharges on the market? now as far as exhuast goes how can i change this.. it has thru the leg exhaust and a switch to turn it straight out the back so not much restriction when i flip it out the back .. once again great advice from everyone and i appreciate u looking out for my safety .. i just want to make sure when i do it right i get all the right parts ! .. and how do i find out if my motor has inconel exhaust valves in it?

I looked that part number up online, and could find nothing that says that it is made of inconel alloy. All of the listings just state that it is the replacement ex valve for the Gen V/VI 454/502 HO engines. I did find this link where a GM tech says that it is just a stainless valve, FWIW => http://www.justanswer.com/chevy/397j...l-stainle.html

I just don't know the real answer, and I'm not a metallurgist. I almost ran the valves that came in my heads. Believe me, I did some digging on the web to try to determine what they are. I even found an article that said you can identify Inconel by the spark pattern when it is held up to a grinding wheel, and I tried this with an old pitted valve from the same heads. Spark pattern seemed consistent with a high nickel alloy, but so did the old garden variety stainless intake that I had laying around. In the end, I decided not to take a chance, and replaced both intake and exhaust valves with a good set of REV's and Ferrea's.

Daniel, what you are describing is the Merc Silent Choice exhaust or the Corsa Captain's Call. Both use a diverter to allow you to direct the exhaust only out the prop or through both the prop and the transom tips. The Merc version uses an air pump and air actuators, and the Corsa uses electric solenoids. I happen to have a set of Gil performance manifolds that came off of a high performance HP500 engine. They have the air actuated diverters built right into the stainless risers. I was going to use them on my boat, but had alignment issues because my boat was originally small block, and the tips were closer together. I may end up selling these down the road.

Otherwise, you may have to ditch the Y-pipe leading to the prop and go thru-transom full time.

who our you guys dealing with for all your aftermarket parts??? for building one of these motors ..i live in canada so if anyone knows a dealer around British Columbia it would be great.. the only real reason i wanted to put a supercharger on first and not just build a crazy motor is because I didn't think the hull would handle all the hp .. was thinking a supercharger would push me into the mid 80s and still hopefully be safe !

If it has the Manley Inconel valves, which I believe is what merc was putting in them, you may see "Manley" stamped into the stem near the tip. You will have to remove the valves from the heads to see this.

Otherwise, as I stated in my reply to Haxby, it is very tough to tell. You'll know they're NOT inconel when a valve head snaps off and grenades your engine for you. There is no more thorough way to completely destroy and engine.

haha oh lets hope that doesn't happen when i do this right lol

Keep in mind though, Inconel or not alot of guys have bolted blower kits to gm mag efi motors and not broke/dropped valves, Smitty

Daniel if you really do want to do it right, search some of articfriends earlier posts. There is probably no one on this board with more first hand knowledge about supercharging a mag motor yourself. He also made a 70mph boat run almost 100 and tuned it himself. FogduckerIII has the same platform as you, did most of the work on his own and has his little Scarab running mid 80's. There are lots of examples..

Good advice - you will find his epic post about oil coolers, oil lines and bypasses pretty useful and interesting. If you don't already have an oil temp gauge, you will probably want to add one after installing a supercharger. As horsepower levels increase, so does heat, and the oil has a large role in helping the engine get rid of that heat, maybe even more so than the water going through the engine. The stock oil/PS combo coolers that are common on the MAG motors are usually not up to the task of keeping the oil temp below 250* or so where it needs to be. This is especially important on a supercharged application.