Putting on different logs and risers
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Putting on different logs and risers

  1. #1
    Seriously off center slowride's Avatar
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    Default Putting on different logs and risers

    I'm replacing the leaky Hardin logs with Harman long bolts which will require re-routing the water lines. It's a 460 with thermostat and is routed with a single hose from the jet pump to the engine water pump plate. Water goes thru the engine to the thermostat housing where it T's with a hose to the front of each log. It circulates to the rear of the log, exits, then goes into the snails. So, this arrangement has cold water entering the engine first, then into the logs (after the thermostat). All my other engines went into the logs first with the pre-heated water then entering the engine.
    Should I re-route the lines so water enters the logs first, or keep it this way? Does the thermostat require the engine get cold water first, or was it routed this way for convenience?






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    Seriously off center slowride's Avatar
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    Maybe this will help
    Name:  route.jpg
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    Jackwagon Patrolman Rexone's Avatar
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    Default Personal preference

    I always like to see warm water from the manifolds entering the engine first (regardless of log maker), through the engine, out through the risers. Just make sure however you route it that the water into the logs goes "in" though the lowest fitting and out through the "highest" fitting so they "fill" with water.

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    tintingsandiego krusn56's Avatar
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    I just got done putting An push locks on mine...Mine goes from pump to valve then to T, logs, block and to then out mani to snails. No restriction and run with valve all the way open all the time. I made a bracket for the T to hang on my front mount in front of oil pan so I could get the lines even as possible.
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    Seriously off center slowride's Avatar
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    I guess the main issue is I'd like to keep the thermostat, but to do that I need to have a bypass. To have a bypass, I should use the water pump plate, but with a single inlet that complicates routing a hose from each log TO it.
    I haven't had this plate off, so I don't know how water is routed behind it. It could be as simple as tapping and plugging the single inlet and drilling and tapping pipe threads in front of each water passage into the block.
    Does anyone have a pic of the backside of this type of plate so I can see how water flows from the single inlet and the bypass?






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    Very Nice Kruzn!

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    Quote Originally Posted by Rexone View Post
    I always like to see warm water from the manifolds entering the engine first (regardless of log maker), through the engine, out through the risers. Just make sure however you route it that the water into the logs goes "in" though the lowest fitting and out through the "highest" fitting so they "fill" with water.
    Not an issue with the Harmans as the ports are side by side. One less thing for me to dealer with.






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    tintingsandiego krusn56's Avatar
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    You want the water to cool the thru bolt log first. If not you risk them cracking. I took this pic of spare parts and dont see how your block off works...

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    Seriously off center slowride's Avatar
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    I have to check your pic tonight at home... it's apparently blocked here at work. From the outside, it looks like the hose to the center would bypass water back into the block before the thermostat opens, then out to the logs (as it's plumbed now), then the snails when the thermostat opens. It's all theory until I can see exactly what's behind the plate, though.
    I doubt plumbing it through the logs first will cause cracking as that temp from cooling the block first isn't all that great (I've checked it). It hasn't in 25 years with the Hardins, but as I mentioned this is my first boat with a thermostat.






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    Quote Originally Posted by slowride View Post
    I have to check your pic tonight at home... it's apparently blocked here at work. From the outside, it looks like the hose to the center would bypass water back into the block before the thermostat opens, then out to the logs (as it's plumbed now), then the snails when the thermostat opens. It's all theory until I can see exactly what's behind the plate, though.
    I doubt plumbing it through the logs first will cause cracking as that temp from cooling the block first isn't all that great (I've checked it). It hasn't in 25 years with the Hardins, but as I mentioned this is my first boat with a thermostat.
    If you need to get more info, shoot me a PM or call. Be glad to clear it all up. Jim

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    tintingsandiego krusn56's Avatar
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    I have seen the Harman thru bolt crack when water flow was reduced...Like when using over transom pipes bolted to logs instead of snails and valve slightly closed. These get way hot and would run water first as the thru bolt are sometimes hard to find for replacement. I have two sets just in case.
    Last edited by krusn56; 05-04-2012 at 04:27 PM.
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    Seriously off center slowride's Avatar
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    Quote Originally Posted by krusn56 View Post
    You want the water to cool the thru bolt log first. If not you risk them cracking. I took this pic of spare parts and dont see how your block off works...

    Thanx Led
    OK... I can see the pic now. Though your plate is different I assume the flow is the same. There are obviously channels in the casting splitting the single entry on top to the ports in the timing chain cover. I don't see that water could enter the center cavity, so I assume the middle port bypasses water the opposite way I was thinking. With the thermostat closed, water flows from the cavity INTO the thermostat housing and out to the logs. But when the thermostat OPENS, then the flow can go either thru the engine, or bypass to the logs. Doesn't seem very efficient other than building heat in the engine. I must be missing something with the thermostat and housing arrangement then. Water will seek the path of least resistance, and unless the bypass is closed when the thermostat opens, it'll want to bypass rather than circulate through the engine.
    I might be better off ditching the thermostat/housing/plate, getting a traditional plate and plumbing it conventionally.
    Last edited by slowride; 05-04-2012 at 04:48 PM.






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    The more I think about it, it's apparent that flow will split when the thermostat opens, but there must be some kind of restriction on the bypass end of it, otherwise if the thermostat opens all the way and too much flow is bypassed the engine could overheat. That may be why it's routed with the cold water into the engine FIRST. Pre-warmed water may not be able to dissipate heat with whatever ratio circulates through the engine.
    Hardin/CP is making this again. I think it's time to make a call.......
    ALSO explains why the logs stay cool. They have bypassed (cold) water circulating through them as well as warmed water from block circulation. The exhaust can NEVER get as hot as the engine.
    Last edited by slowride; 05-04-2012 at 05:07 PM.






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