Exhaust Riser

[Stu Jackson]

Mike wrote:  Quick Update: Reinstalled new exhaust riser/hump hose today and ran the engine for the first time since modification.

Mike:

Did you just do the HH or the new riser?  I just got a new SS riser from CY, and they built one for me with a turn at the inboard end so that the SS goes all the way forward to the engine manifold flange.

Did you DIY?

Any issues in connecting the new riser to the flange?

Would be interested to know - my next week's project.

Thanks,

Stu

[Mike and Theresa Vaccaro]

Stu,

Had the new riser fabricated at a local shop--all schedule 40 stainless.  They re-used the old flange.  It was dimensionally an exact duplicate of the original riser.  Had to then wrap and safety wire (used a fiberglass insulating tape for that purpose).  Also learned that proper safety wiring starts with a double wrap, and then a 1.5" (or so) twist, wrap, 1.5" twist all the way across the riser ending with another double wrap at the nipple end.  Also works well if you tuck the last wrap under and pull through, cut and tuck the end under the last, tight wrap.  Ran the insulating tape to the nipple, the hump hose slips up to the base of the nipple.

Replaced the raw water injection line.  This needs to be wire reinforced hose, a bit on the expensive side, but you'll only need 18" or so.  You may have to loosen the screws on the anti-siphon valve that it attaches to to allow sufficient room to slip the pipe on to the valve--this may necessitate loosening the valve stems from your sink faucet, depending on configuration.  You probably won't have to pull the faucet, just disconnect the water lines and loosen every thing up so that you you move it out of your way.

Don't be afraid to trim the hump hose, as required.  Slip the gasket on the flange (make sure that you've got it on correctly, the exhaust port is offset) and then snake your riser behind the bulkhead and slip the flange over the three studs, allowing the riser to hang off the back of the engine.  Put the hump hose on top of the muffler adjacent to the nipple and the bare end of the exhaust flange and then make a mark where the base of the nipple is welded to the riser.  Recommend you then measure half the distance from the end to the mark and remove this amount from the top and bottom of the hose.  Measure twice, cut once!  Them hoses ain't cheap...After the hose is trimmed, I removed the riser and then clamped the hump hose  securely with two hose clamps to the end of the riser (don't over tighten!).  I also slipped the two lower clamps in place and snugged them so they would slip off and snaked the riser back through and slipped the other end over the muffler nipple.  

Don't forget to orient all of your hose clamps for easy access.  Recommend you then slip the hump hose on and torque the flange nuts.  I believe that the flange nuts are 9/16" (the engine is an interesting mix of English and Metric).  As with any manifold attachment, snug the nuts evenly--i.e., keep working your way around the flange a bit at a time until all nuts are torqued uniformerly.

After the flange is torqued, then tighten the bottom clamps on the hump hose.  The bottom clamp should only be about an 1/8" above the muffler.  I attached the raw water injector hose last, I also used an angle cut at the base where the nipple interfaces with riser.

You might check the hose clamps supplied by Catalina with the hump hose and check if they are all stainless--they might have a non-stainless screw (the ones sent to me did).  Having had enough of corrosion, I only use clamps that are 100% 316 alloy.  Expensive, but I don't worry about 'em corroding.  Corrosion is the root of nearly all evil on the boat...

Drop a line if you have any questions, our e-mail address is vacntess@cox.net.

Cheers,

Mike Vaccaro
"Spirit" '88 Hull 563

[Mike and Theresa Vaccaro]

Stu,

Forgot to mention the coolant.  I used as small plastic hose and bucket and the gravity method from the petcock on the right side of the engine.  Valve on my petcock is a bit odd insofar as FWD or AFT is OPEN and aligned with the drain nipple is CLOSED.  Draining down to the level of the petcock is sufficient, you don't need to pump out all of the coolant (unless you want to flush and change it).  If you note the amount of fluid drained, you'll know about how much you'll have to replace.  I imagine that a gallon of coolant (50/50 mix with distilled water for 2 gallons of coolant) should be more than sufficient if you don't drain the entire system.

To refill, top off the manifold and I use a small hand pump and suck the fluid from the hose attached to the side of the thermostat, reattach and then top off the manifold tank as required.  I have an over-pressure bypass tank on my system, so I've never run into any vapor lock problems, but as with any engine, run it for a bit, check the thermostat operation and top off as required after it's warm.  Without a blow-by, use the petcock on top of the thermo stat to "bleed" the system of any trapped air, as required.  As a technique with small disels, you might bleed and check your fluid (open your cap) at 1200-1500 RPM vs IDLE since the engine runs smoother and there is less sloshing of fluid.

Cheers,

Mike Vaccaro
"Spirit" '88 Hull 563

[Mike and Theresa Vaccaro]

Stu,

One other consider that's come to light after a couple of hours of operation of the new riser:

Monitor your coolant level.  If the machining on the flange/manifold is less than stellar, the only thing preventing loss of coolant into the exhaust is the gasket.  If you've got some type of overflow, just keep an eye on it.  Recommend you go back and re-torque the nuts after a couple hours of serious vibration.

You might consider some high-temp RTV in conjunction with the gasket to "seal" the coolant ports.  Only downside to this would be that future revmoval of the flange is gonna' be tougher...also recommend you have 2 gaskets on hand, just in case.

Also noticed discussion on the board about insulation--a simple wrap (overlapping about half the width of the tape each wrap) of high temp fiberglass insulating tape, secured with safety wire as noted in the previous post works fine.  Keeps the diameter of the pipe resonable, making installation/removal easier and there are no interference problems with the heat exchanger.  Can hold the pipe immediately aft the manifold with the engine at operating temperature, so it provides sufficient insulation.

Cheers,

Mike Vaccaro
"Spirit" '88 Hull 563

[Mike and Theresa Vaccaro]

Ron,

Agree!  

1.  Another option is to have the riser dupliated locally, if there's a shop capable of doing it.  May actually cost more than Catalina, but A) They'll take care of the  flange; and B) The new riser should be an exact duplicate of the old one--so there shouldn't be any fit issues.
2.  Absolutely!  Any good "penetrating" oil should do the trick.
4.  Toressen Marine price was about 4 bucks each.  Might as well order a spare since shipping costs as much as the gasket!
5.  Concur.  Used scotchbrite on a die grinding tool.  Don't have any problems with the new gasket, although I offered up the high-temp RTV as an option.  Machining on the flange and manifold are less than stellar.
6.  Great idea.  If you fabricate the new riser locally, you can specify this when you order.
7.  No idea--have to see the stress analysis.  Seems logical enough, but logic isn't always a suitable substitute for physics or sound engineering practice.  I simply replaced the hose the same spec hose that came off the assembly originally.  However, could be similar to the hump hose (definitely a better idea than the original hose)--bottom line, I was a History major in college... ;)

Thanks for all the help and input!

Cheers,

Mike Vaccaro
"Spirit" '88 Hull 563

[Stu Jackson]

New Exhaust Riser

Thanks for the input, in addition to everything that had been written before (which I printed out and memorized!).

The new riser is in and working successfully.  I had Catalina make a small modification by having the inboard end turn and xtnd all the way to th engine manifold.  Therefore, there is no black iron in the system anymore, and the new riser is either all one piece or has a stainless elbow (hard to tell because it also cam prewrapped with insulation).

The bolts came out easily, only had to whack the flange off with a mallett and a two by four.

I also installed a new 3 inch HX.  Cool runnin' now, you betcha!

I plan to do a Projects writeup with some pictures, since verything that's ever been written is great, but a picture's worth....

Stu

[SeaFever]

Mike V.,

I wanted to resurrect this old topic as I think some more detail around the insulation on the exhaust riser will help the members, specifically myself

Could you post some more detail on the Fiberglass insulation you used to insulate the riser? Where did you get it? Is it something like a tape that has a sticky surface on the back? I have also read of boat builders using some Aluminum Foil in between the wraps...

Here is some background on the project I have coming up. When I replace my A4 with a Universal M25 in the near future, I am planning to replace the old exhaust riser. Although it appears to be holding up, I think it is time for the 35+year old riser to retire. Reading the posts on the forum I have decided to make the exhaust riser from Schedule 40 SS fittings. In fact I have a makeshift one made of Galvanized steel on the M25 in the my garage! Rather than weld the raw water inlet on the riser I am going to use a T flange and a reducer. The reducer will reduce the 1-1/4 NPT to 1/2" and I can then put a 1/2 nipple with 1/2" barb to take the raw water hose from the HE. Let me know what you think of that idea. My plan is to avoid the weld. I might use Schedule 80 for the T part of it. I have located a local supplier where I can get the SS fittings and pipes.

The details from your post above on how you did the wrapping is going to be very helpful. For now I just need the information on what specific material you used for the wrapping and if it is specialized where you purchased it from. I did try to search the forum but could not get more information in any of the other posts.

[Ron Hill]

Mah : The problem with the welded nipple (raw water insert) cracking is NOT the weld. 
The reason the weld was cracking was because Catalina connected the flow from the vented loop to the nipple on the riser, with a stiff wire reinforced 5/8" hose.  The vibration of the engine and riser was more than the weld could take.  I solved that problem with a same length of nylon reinforced hose (much more flexable).  You don't need wire reinforced hose because it's on the exhaust side of the pump with no acute turn.
As added strength, I also put a bead inside as a stake weld, beside the continuous weld on the outside.
If you don't want to use stainless you can use black pipe, but NEVER use galvanized pipe in an exhaust!
Still think you need to join our assiciation!  A few thoughts

[Stu Jackson]

Ron, Mahendra HAS joined the Association.

[SeaFever]

Yup. It's been 2 weeks already

Ron,

Yes, I have read your posts about the nipple and understand how the wire-reinforced hose creates the stress on the nipple. I am planning on using nylon-reinforced hose. Thanks.

What do you think of my plan of using the reducer on a T connection? My thought is that it will be strong and also something that I can easily make and replace if need be. Having said that the schedule 40 SS (or 80) pipes and fitting should last a real long time...

Let me know your thoughts. I want to get some opinions from you experienced guys before I venture forward.

I will await Mike V's (or anyone else's) info on the insulation needed.

Cheers,

Mahendra

[Ron Hill]

Mah : I've only have experience with  a "V" injection of the HX water, but I don't know why a "T" wouldn't work as well. 
I'd make sure that there is at least a 6" drop of the water from the vented loop to that "T"  making darn sure the antiphon works.  The longer that hose is the more flex it has as long as it's nylon reinforced and the less strain (transmitted engine vibration) on the nipple portion of the "T".   
I'd try it !   

[SeaFever]

I am going to try. Hopefully I will get to start my project in a few weeks. I will let you guys know how it goes and post some pictures. Right now I am trying to finalize a buyer for my A4 so I can put my M25 in...

Cheers.

[Mike Vaccaro]

Mahendra,

We used fiberglass tape wrapped around the SS riser and held in place with laced stainless #40 safety wire.  The fiberglass tape works well and we don't use any additional insulation, although you could certainly wrap some additional insulation around the riser.  The only caveat is to make sure that whatever you use is designed for high temperature use.  I also recommend the use of high-temperature silicone in conjunction with the exhaust gasket.  I find that I have to occasionally re-torque the riser nuts.   

Cheers,

Vac

[SeaFever]

Hi Mike,

Thanks for the info. I have used Yamabond 4 on the gasket of the exhaust flange. Yamabond 4 is the OEM version of Threebond 1215 (manufactured in the UK) that is specified by Kubota for engine gasket sealant.

By riser nuts you mean the exhaust flange bolts, correct? I will remember to check them after some use.

I am getting close to my project now. I am most likely going to start my re-power project in the next 1-2 weeks. I found a customer and made a deal for my A4 so now I can start...:-)

Cheers,

[Stu Jackson]

From an earlier Mainsheet Tech Notes article, this is the exhaust riser I purchased from Catalina Yachts and installed in 2003