advice for exhaust ...
 

I am installing Gill Marine manifolds and Stainless Marine pipes on my 311 ..we ran into a couple of problems ... First the pipes are too long and they extend within 3/4 inch of going thru the transom ...I am open for suggestions ...we are looking at a cpl of things. The first would be to just have Stainless Marine cut the pipes ...These pipes have a water jacket all the way to the end and have a 3/4 outlet inside the pipe . Not sure if they can do this . Second option would be to install 5 inch tips thru the transom and let the pipe slide inside the tips ..there would be a 3/8" gap around the 2 pipes which we could fill with hi temp RVT or simular ...maybe even install a boot over the joint ...

Second problem is the pipe needs to angle down to existing Transom holes. Needs about 10-11 degrees . This tranlates into a 1 1/4 inch wedge .. Gill has 3/4 and 1/2 but that would require too many gaskets and seems clumbersome. I am checking into local a machine shop making the wedges but I am open to suggestions ...thanks Mike ..

Re: advice for exhaust ...
 

Mike, do all the pipes go through the original transom holes and end up three quarters of an inch short? If so, why not have a shop weld some new tips on the end of the existing pipes? Seems to me there ought to be a way to "flare" the interior side of some new tips, slide them over the end of the Stainless Marine pipes, and then just weld them together. Just a thought.

On my 242 with twin small blocks, it had a 3 inch pipe. I enlarged the original transom holes to accomodate 4 inch tips, then on the interior had then "necked" down to fit the 3 inch hose from the 3 inch risers. If they could neck down from 4 inch to 3 inch, they ought to be able to neck up just enough for a new tip to slide over. If they went far enough over it you could probably clamp it and not have to weld it.

I'll try thinking on it some more. Russ

Re: advice for exhaust ...
 

Right the pipes are 3/4" short from going all the way through the transom. I would think the tips need to be separate from the pipes ..the tips have the flange that seals the water out ...if these were above the water line you prob could just extend them....

Re: advice for exhaust ...
 

Those tailpipes must've been made for a TRS setup. Have someone weld on a 6 inch extension and use gasket seals at the transom. With those longer tailpipes you'll have less reversion than Bravo style tailpipes.

Re: advice for exhaust ...
 

That's what I'm talking about. Flare the engine side of the tips to slide over the Stainless Marine pipes up to where the flange seals against the transom, screw new tips into place, and then clamp the the "flared" end of the tips around and to the Stainless Pipes. Problem solved, plus by clamping them you can always seperate if need be. I think it'd work just fine and would be an easy fix. Russ

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Most of the extensions I have seen with Gaskets say they are to be used above the water line ...with the silent thunder I wonder if that would be considered above the water Line ?

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Might werk Russ ...Kinda what I was referring to with the 5" tips but your idea might be a better fit ..

Re: advice for exhaust ...
 

Mike, if you flare the tips just enough to slip over the Stainless Marine pipes, you would have a pretty tight fit already. Used to do this all the time on muscle car exhaust systems. That way you also wouldn't have the space to fill by using the 5 inch tips.

My transom holes are probably about 14/16 inches above the water line which seems about standard.

I think it would work out very well with relative ease, also shouldn't be too expensive for the tips. Get hold of Too Old @ Trick Marine here on OSO and let him know what you need. He's out of town until Monday.
He could have Stainless Marine make the tips up and drop ship them directly to you, and his prices are unbeatable. Russ

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Mike,

You might want to check with Bobby at Lake Precision Welding on Crile Road in Cleveland. He did all the welding for Gil when it was Gil. He fixed me up on my 382 tailpipes and has also done work for Wags382. I'm not sure how he is on the internet, but if you can send him pics, he could solve this problem the best and least expensive way. I'l try to get his number to you ASAP.

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Thank ya sir .....Outlaws idea might werk ...It needs to be right and it also needs to be ez to remove ...seems I got a motor out every other month ....

Re: advice for exhaust ...
 

offthefront,

I agree with Patriot. Forget the exhaust tips!---unless of course your bent on having them. Buying 4-tips and then having them welded on is going to cost you more $$$, time and aggrivation (probably A LOT MORE) when all you need to do is have the tailpipe extended 6 inches or so out from the transom---problem solved. Don't make this any harder on yourself than you have to. I am quite sure just having the existing tailpipes extended will be the easiest and most cost effective way of correcting your exhaust situation.

I also agree with RedDog382 about Bob at Lake Precision Welding. A couple years ago my cousin and I both needed tailpipe work done. Mine was a straight pipe application like yours---a no brainer, but my cousin had GIL exhaust manifolds and tailpipes that he bought second hand that were too short and didn't have the correct angle for his application. He called Bob, took some measurements, drew up a diagram and sent all 4 tailpipes into Bob's shop. In addition to needing to have the pipes extended, he ended up needing about 3 angle welds on each pipe to get the correct angle and length to make them fit in and through the existing holes in the transom of his boat. When we got them back my cousin and I looked at each other like "how are these going to fit with all the angle welds?"---but he went to bolt them on and ALL 4 tailpipes fit perfectly through each existing transom hole! The real kicker is that Bob was extremely reasonable with his pricing---especially for what he did on my cousin's stuff!---at least he was with the both of us and he didn't know us from Adam! We just took some measurements, drew up some diagrams, sent him our tailpipe stuff and delt with him over the phone.

Lake Precision Welding, Inc.
7710 Crile Rd. Unit F
Concord, OH 44077
Ph: 440-639-1444 (ask for "Bob")

Re: advice for exhaust ...
 

Cmi, End Of Story.

Re: advice for exhaust ...
 

I'll check with him Monday ...:) .. thanks

Re: advice for exhaust ...
 

Gona Crank new motor Monday ....:)

Re: advice for exhaust ...
 

This is what I did to install my system last winter. I had TRS dry pipes that I shortened, changed to wet and added 2 angles to fit my existing holes. I made all the cuts with a 14" cut off saw. Then brought the pipes to local welding shop to have them MIG welded. I then polished the pipes back to new.
After I cut the pipes I heated the inner pipe and drove a triangle piece of steel into the pipe to expand the inner out the the wall of the outer pipe. leaving gaps for the cooling water to enter the exhaust stream.
The worked great!

Re: advice for exhaust ...
 

Payton ...looks great ..about the triangle .. did you just drive it into the end of the heated inner pipe and then remove it after pushing the walls out ? or is a triangel with a hole to allow the exhaust thru?

Re: advice for exhaust ...
 

Not so fast! CMI's are very nice, but they will be problematic in the 311. Due to the Silent Thunder, the holes through the transom are higher than the standard Bravo holes, therefore there is no downward angle in the tailpipes. This will cause problems with reversion unlees you go to a dry system or dump the water out way past the transom. Trust me, I battled this problem for a couple years in my 311!

Re: advice for exhaust ...
 

Mike,

Are you putting your Silent Thunder platform back on? I was always concerned about the heat from the exhaust burning or melting the fiberglass if the exhaust was not "wet" (cool) enough as it entered the platform. On my 382, I have some rubber collars with stainless flanges with screws to secure them to the outside of the transom. The pipes slip through them and create a seal. Wish I could send you pics, but no digital camera. :(

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Red Dog, I noticed that the rubber exhaust hose does not have much drop on my 311. Why isn't there a problem with reversion with the stock Merc exhaust units flowing ultimately into the Silent Thunder box?

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1.) Cam profiles in the stock motors are pretty mild and not known for reversion.

2.) Are you sure the problems with your engines/valves are not due to reversion?! I think it's unlikely, but I haven't been able to keep up with your postings on the engine/valve problems.

Chris

Re: advice for exhaust ...
 

Chris: Mike (offthefront) has been having the engine problems. I don't have any that I'm aware of. I was just curious why there was never a reversion problem with little drop in the rubber exhaust hose. Mine drops maybe an inch and a half maybe two inches total. Russ

Re: advice for exhaust ...
 

Russ,

Sorry for the confusion ... trying to squeeze posts in at work ("continue CPR ... I'll be back in a minute - gotta go post on OSO!" :D ).

I never had problems with reversion with my stock 454 mags or factory exhaust. I had problems after modifying the motors and changing to CMI exhaust. The higher CMI with 3" rise would not clear the fiberglass lip in the back and the standard rise caused the tails to be almost straight without any downward angle.

I think the factory setup was adequate enough to prevent reversion with stock cams. One has to be careful with modifications ... one change usually means two or three other things need to be changed later to fix the problems resulting from the first! I know your wife understands this ... right?! :D

Re: advice for exhaust ...
 

I wasn't very clear on that was I.
Yes the wedge was simply to drive the heated inner pipe out to the wall of the outer pipe. I was looking for a cone to drive into the pipe and then drill the water exit holes. That is vertually what Gil does. I couldn't find the right size cone to use so I just made a wedge out of 3/8" plate. Heated 2 areas opposing eachother about 1" long and drove in the wedge. Pulled it out and did this again I think 3 times. This kept the inner pipe nicely centered. Factory pipes use 3 holes 7/16" diamater for water exits. I would guess my water exits were about equal to that.

Re: advice for exhaust ...
 

Payton ...got it ..did you weld the inner to outer ? I worry about my pipes being so long that if the inner isnt "tacked" to the outer that it would eventually cause a crack or break somewhere inside the pipe from Vibration ...If you look at the pic these pipe have the water jacket all the way to the end and then the inner pipe flares out to the outer pipe and its welded solid ....and then there is a 3/4" nipple that runs 90 degrees out off the water jacket and flush with end of the pipe ..there is also a small V at the bottom on the inside which I bet causes a spay of water up into exhaust stream for cooling ....

Re: advice for exhaust ...
 

No, I didn't weld the inner to the outer, maybe you should. The small hole in the bottom is to let cooling water circle the pipe and have a little exit on the bottom so there won't be any hot spots on the pipes.
If you look on my pic, the forward engine with the taller risers, didn't have to be changed, they were already wet pipes. The inside wasn't welded, just pressed out to the outer pipe and the 3, 7/16 holes drilled. spaced evenly around the pipe.

Re: advice for exhaust ...
 

Hows this ?