engine/cam/exhaust ??
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engine/cam/exhaust ??

  1. #1
    Senior Member crf311's Avatar
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    Default engine/cam/exhaust ??

    Hey guys, It's been a while since I did anything with my jet boat.. I went to go out on it and come to find out my water jacked headers exhaust had a leak on 2 of the tubes. The water down here just eats this shit up. Since I don't have the money to go with a SS exhaust setup at this time I was looking to change my exhaust to the mercury/gill exhaust set up.

    My question is will I have any water reversion problems with this set up with my cam which is in there now. Here is the spec on my cam. Solid tappet. .615 lift intake .626 lift exhaust. Duration is 249 @.05 intake [email protected] exhaust. The lobe separation is 110 with a 106 centerline. When I built this motor with this cam I was told I would need to use over the transum headers or Water jacked thru transum exhaust

    From what I have found out is when using the log style exhaust is to keep the duration at or below 230. Should a stay with this with spec. with the center riser mercury/gil exhaust set up also.

    Thanks
    Robert

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  3. #2
    Senior Member crf311's Avatar
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    ttt, come on, someone needs to know something

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    Senior Member crf311's Avatar
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    TTY. Anyone??

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    Senior Member wpmxwb's Avatar
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    I ran a bigger cam with logs. I didn't have any problems with water reversion, but they did choke the hell out of the motor. Probably the reason u were told to use a header instead of logs.

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    Senior Member GT Jets's Avatar
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    It has been my experience that the idle will need to be higher than you may want with longer duration cams, with 110* separation I think you will find a pretty good exhaust pulse, but not crazy. That being said, try to get a reference plug installed and throw on an exhaust pressure gauge while idling and "tune out" the pulse.

    That is really all I got.

    Unfortunately it will be somewhat trial and error.
    GT


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    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by crf311 View Post
    Hey guys, It's been a while since I did anything with my jet boat.. I went to go out on it and come to find out my water jacked headers exhaust had a leak on 2 of the tubes. The water down here just eats this shit up. Since I don't have the money to go with a SS exhaust setup at this time I was looking to change my exhaust to the mercury/gill exhaust set up.

    My question is will I have any water reversion problems with this set up with my cam which is in there now. Here is the spec on my cam. Solid tappet. .615 lift intake .626 lift exhaust. Duration is 249 @.05 intake [email protected] exhaust. The lobe separation is 110 with a 106 centerline. When I built this motor with this cam I was told I would need to use over the transum headers or Water jacked thru transum exhaust

    From what I have found out is when using the log style exhaust is to keep the duration at or below 230. Should a stay with this with spec. with the center riser mercury/gil exhaust set up also.

    Thanks
    Robert
    Robert theres some good information on exaust/water reversion right here on PB front page http://www.performanceboats.com/cont...on-review.html as well as on our sight (by Rewarder Headers) that may be helpfull Tom
    Jet Boat Performance, JBP Header Water Reversion info

  9. #7
    Senior Member crf311's Avatar
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    Thanks Guys.

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