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  1. #1

    Yamaha 1100 exhaust routing

    Hey everyone! I've been working on a jet jon project for the past coupe of months. I'm taking the parts out of a wrecked 1995 Yamaha Waveraider 1100 and putting it in a 16/48 jon boat. I have ran into an exhaust issue though. Since I've been fabricating everything out of aluminum, the exhaust is not going to routed exactly the same. My main question is: Does the exhaust need to be above or below the waterline? Or does it matter? It would make things a lot easier if I could go above the waterline in the jet tunnel I made to hold the pump. The next easiest option is to exit out the side of the boat above or below the waterline. Any knowledge about the exhaust will be helpful!
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  2. #2
    raiderteen's Avatar
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    You will want to incorporate the water box(s) into the exhaust to help with keeping the correct amounts of back pressure. Which also means keeping the exhaust below the water line. On the 1100s there are two waterboxes. You can remove the starboard side and only use the port side box while still keeping the U-bend hose then do a custom exit from there. The reason for keeping the U-Bend is to keep water from back flushing into the motor when coming to a stop or floating.

    Keep in mind this exhaust has the cooling water traveling through it as well so isn't inherently "melting hot". I've seen high temp pvc used with success to make 90* bends when deleting the starboard water box. So you can get creative with your routing materials if needed. It looks like you are very skilled with aluminum so that shouldn't be a problem at all. You might even try to incorporate the factory exhaust thru hull if possible.

  3. #3
    Thanks! I figured out a way to get the water box below the waterline. I am able to use both water boxes but it will be easier and take up less room if I use the port side only. Will there be any benefit if I do use to use both water boxes? Will it make a significant difference on the sound level? I'm definitely going to use the factory exhaust thru hull. Dose the bottom of the hole need to be the same level as the top of the water box so the water box can stay filled?

  4. #4
    raiderteen's Avatar
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    I can't answer any of the specifics as to keeping them both level or not when installing the water box and thru hull. I can say from experience that removing one box mostly adds to the sound level with little to no change in performance for the better or worse. It was mostly a "make it sound meaner" modification from my younger days. Definitely more throaty sound with a deep tone down low just before coming to plane.

  5. #5
    I would use mandril bent aluminum tubing from ptstubebending.com for the exhaust piping, with rubber hose as couplers. I have had the rubber hose burn up on the outside of bends before, which isn't fun in the middle of nowhere. I also prefer to thru hull down low as it will somewhat aide in keeping the noise down.

  6. #6
    Thanks for all the advice. I think I will run one water box for now since I already have all the materials to make it work. I just have to make the decision as to where to drill the holes for the exhaust thru hull. In the picture, I have it set in place and I have everything as low as I can get it. Its 2 inches from the bottom which should be completely submerged. Thanks for the link. I will defiantly order some bends if I decide to run 2 water boxes
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  7. #7
    raiderteen's Avatar
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    That looks like a good solution. Some aluminum mandrel bends would clean up the look for sure but that will function perfectly as shown. I feel given your setup that two waterboxes would be very cluttered. I don't know your intended use for this john boat but that area to the starboard side of the pump would be a great spot for a live well I would imagine.

    One thing to make sure you do is use that box in the same flow direction as it was in the ski. I can't say 100% but I would bet the baffles inside are designed to flow better in one direction over the other.

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