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  • Exhaust Manifold/Tip/Piping Upgrade

    • Year: 1987 Brand: Malibu Model / Trim: Sunsetter Cost: $1500-$1999 Engine Type: 5.7L Mercruiser Comp Ski

    On of the cast iron exhaust manifolds on my 1987 Sunsetter started leaking.  Something failing is the boat’s way of telling me to upgrade it right?  ?  I started shopping around a researching exhaust manifolds and chose two Stainless Marine manifolds.  I’ve been very happy with the choice!  A user on TheMalibuCrew, “Woodski” shared some info on how he made “mufflers”.  Everything is 4" from the mani's back. The "mufflers" are 1/8" stainless plate cut into 4" circles with 4 tabs that are bent back over the exhaust tube. There is a half moon cut out of the circle for the exhaust gas to flow through. I still need to cut slots in the bottom of two of the muffler plates to allow water to pass through the solid half. The design allows me to slip the coupling over the end of the exhaust tube and capture the muffler. Basically the idea is to keep the line of sight broken for the sound waves to exit the exhaust. If you shine a light up your exhaust, you'll see a similar design, but a bit more restrictive.  Now, on to the install!
    Existing exhaust....





    Old mani's off...
    New manifolds on!  Still need to sort out the cooling water plumbing.
    "Muffler" plates...
    I also upgraded the tips since I am running 4” instead of 3” exhaust.  I’ve always thought with the custom stainless wedge bracket that a pair of stainless slash cut tips would look awesome on the boat.  I drew up a drawing for what I wanted and sent it off to Stainless Marine and they custom build a pair to fit the boat.  As usual I couldn’t go off the shelf.  Since the flange needed to be angles a bit to fit the transom angle and the flange needed to be a bit smaller than the standard offering to fit the flat spot on the older style transom a custom job was in order.  Stainless Marine did an awesome job.  Check out the pics below to see what they look like.  One thing worth mentioning, old sealant and silicone is tough stuff to remove.  When mounting something to the transom of a boat that is going to be below the waterline, surface prep is very important.  To remove the sealant from the old tips I tried everything….Goo Gone, Goof Off, Brake Kleen, and Gasket Remover. Nothing phased the silicone. It is good stuff. I worked at it for a long time with my fingernail and a few more razorblades. I was pretty happy with how clean I got it and siliconed in the new tips with 3M 4200. 
    After the tips were mounted I headed into the boat and hit the first obstacle that I knew was coming. The tiller arm cleared the old exhaust by 1/8". The new stuff is 1/2" thicker so I knew I was going to have to take 1/2" off the tiller arm and machine a new hole for the control cable. I bought a newer Malibu rudder, housing, and tiller arm from TheMalibuCrew’s Chris's wrecked Sunsetter so I figured I would install it while I was at it. I got everything on my old rudder off EXCEPT the base plate on the bottom of the boat. I banged, pryed, heated, yelled, bled, etc and it would not budge. I called rugger to see if there might be 5200 holding it on, but he said he hadn't taken it off so whatever Malibu used is good stuff. My Skier's base plate came off easy....not this one! rugger talked some sense into me....since the dang thing has been on the boat for 24 years and works fine I put it all back together with new silicone inside the boat. Heck, the wheel turns with one finger. Another good thing is the rudder shaft on the old rudder is 1.125" and the new one is 1". Also, the bore going through the bottom of the boat needs to be larger for the new port...no biggie, just another thing to change. I'll save the new parts in case I ever ding my rudder off something.
    Anyways...here's the pics from the tiller modification.
    Tiller arm too long...



    Much better…

    Newer Malibu rudder shaft….

    Existing 87’ rudder shaft

    Existing rudder left, new one right (I think the existing one looks like it has more steering authority with the longer blade)...

    New port vs Existing port...the grease zerks are the whole reason I wanted to change the port...

    Got the main tubes and "muffler plates" in. It is turning out nice. Just need to add the 4" tubes to get me up to the manifolds and I'm done with the exhaust piping. I then have to sort out changing the hosing for the cooling water. Getting closer!


    Got the down tubes installed. I feel like I've been wrestling pythons to get them in there.  I think it looks pretty sweet. 
    I ordered softwall tube and I thought that was a mistake. The left (port) tube for some reason wants to flatten out more than I would like.  I ended up putting a band clamp around that section of tubing to help keep it round and it has worked well.  Just a though when debating between hard and softwall piping.


    Well I got the cooling water all hooked up and everything looks, works, and sounds awesome! A couple quick revs in the driveway put a big smile on my face. Can't wait to hear it in the water. As you can see in the bit I stuck the camera in the boat, the downslope of the exhaust in out inboard boats really amplifies the water acting as a muffler since the water actually hangs near the 45* coupling since it is lower than the tips when the boat is floating or on the trailer. Under way, the tips will be lower.....and the exhaust louder.  I can't wait to hear it from the slalom rope!
    Enough talk about exhaust….let’s hear it!!

    After the first night on the water with it I think it sounds fantastic. Much deeper tone than before. It is louder as well, but certainly not overbearing. It would turn your head if you’re a motor head like me. 
    What I can't believe is how much faster the boat pulls out of the water with the wedge down! I actually gained 3 mph on the top end as well! I'm pumped with the install and very happy with the performance outcome. The video doesn't do the sound justice, but gives you an idea.

    Of course the fly by vids are the best….. Excuse the camera shaking.....water was 59 at the dam and I was just floating with trunks on.  This video isn’t about the picture....it’s about the sound! 



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