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Thread: Looking at building an engine for my boat

  1. #1
    Member avidflyer's Avatar
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    Default Looking at building an engine for my boat

    I have a 28' carver that had a single 350 in it (boat has not been in the water in 15 yrs and engine was blown when I got it). I am looking at building a 383 to give me more Tq and hopefully more prop. I know I am not the first guy to do this, and I am hoping someone out there has built one and had good luck with it hold together. What cam, intake, heads etc did you go with and what kind of fuel burn numbers are you getting? Did you notice a big difference in power?

    Thanks

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    Member Dirtofak's Avatar
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    Have you looked at ordering a crate motor? Balancing the time, warranty etc.....

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    Member Dupont Spinner's Avatar
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    Being that the boat has not been in the water in 15 yrs, you actually should consider a complete repower, engine/outdrive. You may find your outdrive maybe outdated and an increase in HP/TQ could put it to an end it's life. Check a few places in state to see what the shops say about your unit and parts availability.

    Weigh all options and ensure once you make the investment that you are going to get some life out of it.

  4. #4

    Question

    How important is torque to a boat motor? I know torque is important to vehicles that want to come off the line faster for drag racing, however, isn't getting up on step (if that is your concern) a matter of hitting your power band with a larger pitched prop? I would be more concerned with increasing (not shifting) your power band into the lower rpms with a new cam shaft. I would think this would probably give you more overall performance and better gas milage. I am no motorhead, so consider my source.
    We never really grow up, we only learn
    how to act in public

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    Member avidflyer's Avatar
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    I will be pulling the outdrive off and going through it as well this winter. I have almost everything new for the engine (raw water pump, heat exchanger, circ pump, manifolds (aluminum and stock cast) risers etc. The engine I have now has LT4 aluminum heads, but the guy cant remember who built the engine or what the specs were.

    Doug,
    Getting out of the hole and on step is a major concern of mine, and I am surprised that the 350 was even able to do it. I know from past experience with a 28' bayliner, that the 350 would get it on step with full fuel and 2 guys, but add a few fish, or another person and forget it. Since I have a new engine on the stand ready to drop in, now is the time for me to tear it down and build (or atleast check to see what I have) so I am looking for advice on what others have done before me. What Cam etc was used etc.

    Thanks.

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    Member SusitnaAk's Avatar
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    Try here i know that i have read alot on this in the past, Didn,t have much luck in the search engine thing, for the exact thread, but if you dig around I,m sure you will find some stuff, Seem,s they take 350, put 400 crank in it play with the block, can,t rememeber all details.
    http://www.riverjetmagazine.com/fuse...=59&entercat=y

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    Member hoose35's Avatar
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    I would think that for a 28' boat with a single engine application, you want to go with a 454. I have a 28' glasply, and it has twin 350's. I just don't like the idea of having to run your engine hard all the time, I really doubt you would get that much better performance out of a 383, than you would in a 350.

  9. #9

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    [QUOTE=avidflyer;793537]I have a 28' carver that had a single 350 in it (boat has not been in the water in 15 yrs and engine was blown when I got it). I am looking at building a 383 to give me more Tq and hopefully more prop. I know I am not the first guy to do this, and I am hoping someone out there has built one and had good luck with it hold together. What cam, intake, heads etc did you go with and what kind of fuel burn numbers are you getting? Did you notice a big difference in power?

    I started the 350 -383 thread in the Modifications Forum. My re-power hasn't been pretty but I don't believe it had anything to do with the 383. I chalk it up to my inexperience and just bad luck. I finally drove my 21 foot jet boat yesterday and noticed a huge difference in initial power and acceleration. The added torque turns the bigger impeller with ease. I'm running faster at lower rpms and getting up on step much faster. I don't know the specs. inside the motor. I just ordered the 360 hp 383 long block from US Engines. It burns regular gas.

  10. #10
    Member avidflyer's Avatar
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    [QUOTE=Boud'arc;796546]
    Quote Originally Posted by avidflyer View Post
    I started the 350 -383 thread in the Modifications Forum. My re-power hasn't been pretty but I don't believe it had anything to do with the 383. I chalk it up to my inexperience and just bad luck. I finally drove my 21 foot jet boat yesterday and noticed a huge difference in initial power and acceleration. The added torque turns the bigger impeller with ease. I'm running faster at lower rpms and getting up on step much faster. I don't know the specs. inside the motor. I just ordered the 360 hp 383 long block from US Engines. It burns regular gas.
    Thanks, I read your thread and I have a brand new engine sitting on the stand that came with the boat, I am just wondering what Cam you have? Did you get a build sheet with your engine that shows what is in it? I have the crank ordered etc. just waiting to figure out what Cam to put in it and I did not want to re-invent the wheel.

    Thanks

    Leni

  11. #11
    Member Dupont Spinner's Avatar
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    [QUOTE=avidflyer;796605]
    Quote Originally Posted by Boud'arc View Post

    Thanks, I read your thread and I have a brand new engine sitting on the stand that came with the boat, I am just wondering what Cam you have? Did you get a build sheet with your engine that shows what is in it? I have the crank ordered etc. just waiting to figure out what Cam to put in it and I did not want to re-invent the wheel.

    Thanks

    Leni
    Go with a marine spec cam or what many consider a 4x4 cam. Basically a cam with little overlap around 110* lobe seperation. Also look at a cam that will have all it's power before 5000 rpm's. It should provide a smooth idle. This should put your best torque close to your cruise range.

    That Carver is a big heavy boat. A friend had one with the Ford engine. It had many problems with water in the tank, which turned out to be a problem with the tank vent.

  12. #12

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    avidflyer,
    I don't know the specs on my motor. Alaska Drag Bike (ADB) in Anchorage was very helpful to me. They build 383s and may have some recommendations for you. US Engines are also very helpful on the phone and may give you the specs. Just remember that anything over the 360 hp range will require premium fuel and in US Engines words "is a toy".

  13. #13
    Member avidflyer's Avatar
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    [QUOTE=Dupont Spinner;796628]
    Quote Originally Posted by avidflyer View Post

    Go with a marine spec cam or what many consider a 4x4 cam. Basically a cam with little overlap around 110* lobe seperation. Also look at a cam that will have all it's power before 5000 rpm's. It should provide a smooth idle. This should put your best torque close to your cruise range.

    That Carver is a big heavy boat. A friend had one with the Ford engine. It had many problems with water in the tank, which turned out to be a problem with the tank vent.
    I will check out the vent. I had issues with the same thing on a 32' commercial boat I had!

    Quote Originally Posted by Boud'arc View Post
    avidflyer,
    I don't know the specs on my motor. Alaska Drag Bike (ADB) in Anchorage was very helpful to me. They build 383s and may have some recommendations for you. US Engines are also very helpful on the phone and may give you the specs. Just remember that anything over the 360 hp range will require premium fuel and in US Engines words "is a toy".
    I talked to US engines several times, and told them I was going to put a MPFI system on it from Affordable Fuel Injection and I needed the cam spec so they could build the fuel map for it... They were not real willing to give out the info. At that time I was talking about buying the same engine from US as you did. I will give them another call tomorrow and see if they will help me out.

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