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  1. #1

    Exhaust Riser Problems

    I need to get smarter about problems with "risers". Is this just a saltwater problem? How do you know when it is time to replace? What changes and why? I guess the problem is caused by corosion just beyond where the anti freeze is. I have seen several threads that talk about oil changes and riser replacement in the same sentance. People I talk to in the Detroit area just shrug their shoulderas. No one here has ever replaced a riser that I know of. I might move my '86 36C Crusadrer powered Hat to Florida so I need to learn about this problem.

  2. #2

    Re: Exhaust Riser Problems

    If you don't know when the riseres/elbows were last replaced, replace them. In salt water, replace the risers/elbows at least every 5 years. There is no way to know if they are bad until the go and when they do, it's too late.

    First I suggest reading this if you haven't already:

    http://www.yachtsurvey.com/exhaust_risers.htm


    As Pascoe points out, old Crusaders had excellent risers. They are not very expensive (as far as boat stuff goes), I replaced all 4 risers/elbows and related gaskets in 2003 for about 850 bucks. It is not at all difficult technically but it can be quite labor-intensive if the risers are original because it is common for them to bind on the 8" long studs that hold them on. They can be EXTREMELY recalcitrant about coming off! This is one instance where a BIG HAMMER with a relatively soft pounding surface will be very useful - perhaps even mandatory. When you replace the risers/elbows you are going to slather plenty of anti-sieze compound on the new ones!!

    I've done my own risers several times on different boats and have helped several other folks replace theirs (as recently as NOV 05) so don't hesitate to email me if you have any questions that I might be able to help with.

  3. #3

    Re: Exhaust Riser Problems

    I originally had 454 Crusaders in ELECTRA VI. I am in Southeast Florida and religiously changed out the risers every five years. Had one go on my 30 Chris Tournament Fisherman, but that happened while she was in the yard and they took care of it immediately. Never wanted one to go on me and have to suffer the consequences. Let me suggest that when you do change them, that you have another pair of hands. Trying to do it without help is a real PITA. I know, I did it twice.

  4. #4

    Re: Exhaust Riser Problems

    Maynard::

    They last indefinitely in fresh water.

    There are many old cruisers running around the Niagara River from the 40's, on up, same original risers and engines for that matter. A friend of mine just rebuilt a 1920 Buffalo Made Sterling, the risers were fine. What a beauty, going into the Miss Saint Lawrence a Hacker design 35 foot speed boat.
    Tony D

  5. #5

    Re: Exhaust Riser Problems

    Quote Originally Posted by ELECTRA VI
    I originally had 454 Crusaders in ELECTRA VI. I am in Southeast Florida and religiously changed out the risers every five years. Had one go on my 30 Chris Tournament Fisherman, but that happened while she was in the yard and they took care of it immediately. Never wanted one to go on me and have to suffer the consequences. Let me suggest that when you do change them, that you have another pair of hands. Trying to do it without help is a real PITA. I know, I did it twice.
    OK, Now I don't think we have to worry until after 5 years in saltwater as our 36C has never seen salt water. What happens when they "GO".

  6. #6

    Re: Exhaust Riser Problems

    You don't wait for it to go because you can end up with water in the engine oil or worse in the cylinder itself and Bye Bye block!

    Five years in salt water is a good frequency for replacement of the risers and same for the manifolds if it was a raw salt water cooled engine. Are you sure about the history of the boat in fresh water?

    Nick
    Last edited by Nick; 01-10-2006 at 12:04 PM.

  7. #7

    Re: Exhaust Riser Problems

    Thanks Kick...Yes the boat was trucked to Toledo Beach Marina in 1986 and was there when I bought it. I am my own mechanic for all systems and I have never found any sign of salt water problems. Our window tracks needed severe cleaning, rubbing strips, and fuzzies, but the original anodize is like new except for a little sun fade.(The sun does shine occasionally in Detroit, but not in winter). The other reason our boats stay nicer in general is that we only have them in the water half the year. Ours has 800 hours total since new and that is very common here. That is probably why most new purchasers opt for gas engines. they are used so little that the diesel option is hard to justify. Our insurance is less than half of what it is in Florida.

  8. #8

    Re: Exhaust Riser Problems

    take them off every year and acid wash, replace every 5, replaced risers, upper and lower elbows 1.5 yrs ago, boat kept in st lucie river which is primarly muddy fresh water comming out of lake okeechobee so we did not acid wash last august. however now we are in the salt water and plan to do it this summer. When we replaced them I painted them with alot of paint, I mean alot like about 1 can for 2 pieces. baked them in the oven to harden the paint then installed. You should pull manifolds and have them resurfaced although we did not. instead I got a diamond knife sharpening block and smoothed the gasket surface. our surfaces were a little pitted. Osco does not recommend using any compounds on the gaskets. however we tried anti sieze on the manifold surface and it has been fine since. Anti sieze is waterproof grease so we thought it would assist in stopping surface rust. Mike, jump in if you think this was bad idea.

    All that said, replace the risers and elbows when you move her, this is relative cheep insurance just like more than required oil changes.

    attached is a web site that I got my Osco replacements from.

    http://marineengineparts.com/shopsit...ml/page14.html

  9. #9

    Re: Exhaust Riser Problems

    When they go, water can get into the cylinders and that is something you don't want to happen.

  10. #10

    Re: Exhaust Riser Problems

    I have owned a 1965 Chris Craft Seaskiff with twin FWC 327 V-8 engines since 1986 - 20 years (just sold, thankfully, as owning 2 boats is not twice as much fun as owning 1), so I've had a little experience with risers. I agree that the long studs can be a pita when it's time to remove them, but not neccessarily from crud, although that does contribute to the problem. One of the obstacles to removing them is gravity - a fact often overlooked by mechanics. Those suckers are fairly heavy, and their weight pressing down on the studs impacts their removal. What I have done is to place a small bottle jack under the aft end of the risers, and apply slight upward force on them. Taking the pressure off the studs can make all the difference in the world.

    Next take the slimmest screwdriver you have, and use it as a wedge between the riser and the gasket, and tap it down into the crevice. Try to avoid the manifold side of the gasket. If you chip anything in the process, you want to chip the riser that is being replaced, not the manifold. Once you get a gap opened up, try to pry off the risers, rather than pound them with hammers. If they absolutely won't budge, apply a bit of heat, but do so judiciously, as it is a gasoline boat after all.

    Another approach is to lock two nuts on the end of the stud, and try to turn the entire stud within the riser, and actually unscrew the stud from the manifold. This doesn't usually work, but hey, it's worth trying.

    With respect to the frequency of replacement, I only replaced mine as they failed. I would only recommend this if you are very much "in tune" with the operation of your engines. They WILL warn you that they are failing before they cause catastrophic damage, but you have to be listening.

    The first warning is a slight skip - a missing cylinder - on either cyl 7 or cyl 8, depending upon which riser is failing. This occurs at startup, and clears up quickly. The engine starts running on all 8 again, and sounds fine. What has happened is that a small amount of water has worked its way past an open exhaust valve and into the cylinder. Once it is expelled by compression, the cylinder begins to fire again. To verify that this is the problem, let the engine sit overnight. Now, before starting the engine first remove the coil wire, and then remove the sparkplugs from the rear 2 cylinders. Crank the engine and observe to see if water is expelled from one of the cylinders.

    On rare occasions, I've had water accumulate in cyl 6 or 5, if it happened that the exhaust valve on 7 or 8 was closed at the time the engine was shut down. That usually doesn't happen until the riser is leaking quite badly.

    If left un-corrected, enough water will accumulate to prevent the cylinder from firing at all. If still left uncorrected, enough water will accumulate to bend the connecting rod on a compression stroke.

    Good luck with the project.
    Bob

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