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  1. #1

    Default Tiara 3500 - 1999 Exhaust Question

    I have a 1999 3500 with twin 370 hp Cummins. Here is my question. The engine exhausts go into a large cylinder. Near the bottom, there are two hoses that expel water out two ports on the side of the boat near the water line. The top of the large cylinder (2) has a large exhaust pipe that goes to the back of the boat and expels exhaust under water. So it appears I have 2 exhaust ports on each side of the boat and 2 under water in the stern, or 6 exhaust ports total. While under way at speed, water pumps out the side and I assume water/exhaust also expels out the large flanges under the stern. At idle, it appears water only comes out the sides.


    Why do I have 6 exhaust ports? Someone told me that when I get up to speed, the side ports shut down and everything comes out the back under water. That is not the case. What is the purpose of this set up and how does it operate? Another issue is exhaust soot and grime on the hull around the 2 ports on each side of the boat. A couple of mechanics have told me there is nothing I can do about it, except clean it. Is that true?


    I am sending this same post to Tiara tech for advice and will share that with you. Thanks for help from whoever is on this site.


    Trip Ames
    415 435-1602

  2. #2
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    Default Re: Tiara 3500 - 1999 Exhaust Question

    The two above water ports are probably for 'pressure relief'. Your engines will not like having to push the exhaust out against the water pressure on the underwater exhausts when you are not moving or at low speeds. Once you are moving at speed the 'venturi' effect on the underwater exhausts will allow most of the exhaust to exit via the underwater ports and little will come from the above water ports. I do not think that you can change this.

  3. #3

    Default Re: Tiara 3500 - 1999 Exhaust Question

    Quote Originally Posted by aliboy View Post
    The two above water ports are probably for 'pressure relief'. Your engines will not like having to push the exhaust out against the water pressure on the underwater exhausts when you are not moving or at low speeds. Once you are moving at speed the 'venturi' effect on the underwater exhausts will allow most of the exhaust to exit via the underwater ports and little will come from the above water ports. I do not think that you can change this.

    Thank you. At top speed, water still shoots out the side ports. And I assume through the underwater exhausts as well.

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