Exhaust Replacement

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    Paul Bulk

    Hello. The FRP exhaust piping and some of the hosing on my 2001 32 is starting to fail, due to high temperatures before. Testing shows a max temp of 220f so I will be installing a Vetus mixer to help with this. I want to change the FRP out for silicone or rubber but how do I couple these hoses/elbows together?

    Bob Tilley

    Hi Paul, likewise my 2001 32,Weston Merrit,  had the FRP exhaust leaking due to either age or heat or a combo. The inspection missed the mixer needing replacement.,ah S7(=+-$3$$$.  I replaced everything from the turbo to the back cabinet.  The new rubber hose slips over the 90 degree elbow & the FRP pipe.  I placed the Vetus mixer inside the new hose just after the 90 degree elbow. I also put anti crush sleeves inside the 90 elbow and the FRP at the rear section.  I installed 2 heat gauges – one in the mixed and the other after the 90 degree elbow but prior to the mixer.

    I couldn’t find a competent shipright so ended up during it all my self. Good luck

    Bob & Linda Tilley , Port Townsend

    360-531 1322.

    Tom Easterbrook

    Hi Paul,

    I posted the following on sentoa.org to try to help with your issue. The danger I talk about and that Kelly describes in his article (link below) on NT 37’s is very real and applies to many boats, not just NT’s and not just the 37!! Take the time to look this up, as your engine and/or turbo could be in danger??  If your exhaust system is seeing temps after the “water mixer” above 200 degrees F, this is way, way too hot. However, the big danger is the possibility that water could enter the engine basically destroying it, if you have a similar exhaust to what Kelly is showing in his article. See photo for an example of an exhaust with a problem “waiting to happen”.Doomed to fail exhaust (stock on older NT's)
    I strongly recommend further investigation into potential exhaust system issues. See both the attached articles (even though the NT 37 is a different model the type of exhaust elbow maybe the same) for some good info.
    On my 2002 NT 37, shortly after buying her, I installed an exhaust hose temperature alarm. As it turned out, this probably saved me from a potentially really big problem. During our first summer, the alarm sounded. I carefully checked all engine temps using an IR temp gun, and found all to be well within expected range, except for a few spots on the exhaust hose. There were several spots reading way too hot (and these did not reach 220 degrees). Running that hot can cause the hose to delaminate leading to a possible full hose failure (resulting in exhaust gases and extremely hot salt water leaking into the boat). This is also the very first area where an overheat from almost any cause will first show up. So I highly recommend the installation of this type of alarm. The early alarm can save expensive engine damage, as relying on the regular factory alarm could be too late to avoid damage! The actual cause of my hose overheat was the fact that my exhaust elbow (that looked almost new on the outside, had developed interior perforations (resulting in INTERIOR leaks) that greatly reduced the effectiveness of the cooling spray pattern. This leak could have also allowed seawater to enter my turbo and maybe even my engine through the exhaust if I had not noticed the problem (due to the newly installed exhaust hose alarm)!! Water flow everywhere else was great. To be clear, this type of failure (in the worse case scenario) could result in the need for a new engine if the situation allowed seawater to enter the engine!! There would be no visible signs.

    Also see sbmar.com (Seaboard Marine) under “Tony’s Tips” to read up about “doomed to fail” exhaust systems. My exhaust elbow, like Kelly’s (the author of the attached article regarding his NT 37) was a “doomed to fail” situation. Even these elbows made from stainless steel have an operating life and require replacement as ongoing maintenance, not to mention the “doomed to fail” setup. I used National Marine exhaust out of Marysville, Wash. to design and build a custom exhaust elbow for my boat and was very pleased with the result. The alarm I mentioned is inexpensive, and easy to install. Both Borel (the one I used) and Aqualarm sell models of this alarm. I also installed an Aqualarm water flow alarm between the sea strainer and the water pump to detect instantly any lack of water flow (that could be caused by forgetting to open the sea cock, some sort of external blockage like a plastic bag or seaweed, or a blocked cooler somewhere in the system). Again, not too expensive and very effective.


    I hope this info proves helpful to you and other NT owners (of older boats). I found Kelly’s article to be very, very helpful.
    Tom Easterbrook
    formerly Pilitak NT 37-068 (2002)
    Nanaimo, BC


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