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  1. #1
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    C-18 Performance Mods

    I restored a 16 last year and this year I purchased the boat I plan to keep for a while, a super low hour, pristine 2005 C-18. It came with the Mag 350 MPI/ Alpha package, captains call, transom mufflers. I am in Denver and most of the lakes we run on are above 4,000' elevation. The 18 is nice with the MPI setup for changing altitude, but just not enough power at altitude for serious man fun.

    Over the winter I am planning a major performance enhancement of the power unit/drive and i wanted to see if the knowledge base here agrees with my approach to this boat. We travel a lot to different lakes throughout the west and the 18 is the perfect size boat for our use. We do a fair amount of pulling skiers and toys so the boat needs to be pretty versatile. I like everything to be fast so it needs top end. Here are my requirements:

    1. 80mph at any altitude. Retain factory fuel injection system and run on pump gas. Retain the single point water drain system.
    2. Good hole shot for pulling skiers
    3. Nice cruiser for evening wine cruises with the wife and friends. Not too loud from inside the boat, sounds great outside.
    4. A performance transom look, but with a swimstep for water/ beach loading.
    5. Not concerned about spending money to do it right
    6. Good ride, handles great at all speeds
    7. Good reliability and room for performance growth
    8. Basically, your classic sleeper that delivers surprises and smiles

    Here is my plan:

    1. Keep the 350 Mag as is (75 hours) and add the whipple supercharger kit for the late model MPI system. Add an oil cooler. I already installed SM exhaust manifolds and the mercuiser Smart Vessel Mobile. The whipple setup nets 450Hp with almost no loss at altitude and loads of torque. From what I have read, 450hp should get me to 80 no problem. I'll add Livorsi fuel pressure guage and boost gauges to the dash.

    2. The Alpha should really go because of the whipple, so I am planning on replacing it with a Bravo X 1.5. I'll pull the motor and replace the transom assembly with a new Bravo unit. I am thinking of keeping the Bravo lower because of the pulling and not go with a shortie given that top speed is not the only goal. Either a Mirage + or Hydromotive IV prop, and drive shower. While the engine is out I will probably just remove the through prop exhaust option and run transom only. The stock Corsa mufflers are quiet enough. Add Bravo sea pump and plumb for transom hose hookup.

    3. I already purchased a set of Mayfair 12" K planes. I am going to set them up so I can still fit a set of Imco steering rams on the transom and run the Brazil cable setup for the steering. Looks like the outer edge should be right over the outer chine.

    4. I want to add a pair of Eddie Marine billet swim platforms (red) under the exhaust mufflers right above the waterline. In the west you are always on a beach, and in the water, so you need to be able to get in and out from the back. I have looked at all the options and this seems to make the most sense to me. There is just barely enough room on the transom to do this along with everything else when planned together.

    5. To round things out I already acquired a Hardin marine set of billet controls, new Sony satelite/ USB/ Bluetooth head unit, wet sounds speakers, 10" powered sub, Accon pop up cleats, Accon pop up LED bow light, and steering wheel mounted trim controls.

    So here are a couple of questions. Does this plan seem to be the correct approach to achieving my goals? Would a shortie make the boat basically non-skiable? I am really shooting for an epic classic here. Something that really stands out but is good for more than just fast passes.

    Thanks for the reactions and input.

    Chad
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  2. #2
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    Hopefullyosur866 will see your post. He has tremendous experience with where you are going. Is that an "open channel" steel trailer? I have been looking for one, who makes that?
    1972 16 OB - C16B-63 - "Surface Tension" Resto Project
    1974 16 OB - DMR16106017-B - "The Mule"

  3. #3
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    Yes, osur866 seems to have the most experience here, along with Skilling. I have read most everything he has posted on his development. I am most interested in his opinion on stock Bravo vs shortie lower and effect on pulling skiers/ toys.

    It is an open channel trailer. It is a Trail Rite out of Santa Ana, now out of business. Performance trailer in SoCal has taken over most of their business.

    It has the folding tongue and surge disk brakes. The boat sits at a nice rake on the trailer and low in it for easy deployment. I added the ratchet tie downs and the F2 winch. I also clear filmed the fenders and forward rails to protect the paint. It tows like a dream.

  4. #4
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    Instead of going with a bravo water pump I would go with a crank mounted one.
    You won't have to worry about your present serpentine set up and impeller changes will be much easier. Also , I would consider drive ratio. If you were to drop down to a 1.36 that would put a lot more propellers in the mix. Having said that , there very well could be a good reason most use a 1.5 ... Also , Mercury used a 1.68 ratio for altitude so do a little digging on that subject. First and foremost you are going to want to check your bilge for cracking around the stringers where the L brackets are bolted. My 2004 18 had some cracking in the bilge area that needed to be fixed. The old saying safety first applies here. You need a full hydraulic steering setup , not the cable driven kind. As others have said , Steve will be a great resource to you !!
    better to die on your feet, than live on your knees

  5. #5
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    Quote Originally Posted by smokediver View Post
    Instead of going with a bravo water pump I would go with a crank mounted one.
    You won't have to worry about your present serpentine set up and impeller changes will be much easier. Also , I would consider drive ratio. If you were to drop down to a 1.36 that would put a lot more propellers in the mix. Having said that , there very well could be a good reason most use a 1.5 ... Also , Mercury used a 1.68 ratio for altitude so do a little digging on that subject. First and foremost you are going to want to check your bilge for cracking around the stringers where the L brackets are bolted. My 2004 18 had some cracking in the bilge area that needed to be fixed. The old saying safety first applies here. You need a full hydraulic steering setup , not the cable driven kind. As others have said , Steve will be a great resource to you !!

    Thanks! I will look into all of the above.

  6. #6
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    What is wrong with using a Brazil Manifold to control the steering rams? Is the main goal to get rid of the cable system altogether?

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