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BBC Newby

  1. #1
    83 Crusader - 468 BBC SNiC's Avatar
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    Default BBC Newby

    Hey Guys,
    Just jumped into the "jet world" an bought my first and I will need your help form time to time.
    I am going through the boat and fixing things and here are the first couple of items I need a little advice.

    Running a 454 BBC, bored 30 over.
    Appears to be a nice setup, but the previous owner of 12 years may not have been too sharp.
    He took out the thermostat and controls the water flow with a manual valve on the water inlet. He told me he opens and closes the valve to get the temp running 160-175. I believe I need to replace the thermostat and open the valve.
    Correct? and What thermostat would you recommend?

    He also needed to replace the alternator and could not find the "Motorola" brand that was in it and replaced it with whatever he could find in his small town on a saturday afternoon. At this time I do not know what brand and type he replaced it with. After replacing it , he said the gauges have gone screwy and jump all over. He also said then engine would not turn off until "at someones suggestion", he put a diode in the line. This tells me his new alternator did not have voltage reg in it. Is my assumption correct? What alternator would you BBC owners recommend, or is this not my problem ?

    TIA!
    and any additional suggestions and comments are welcome!

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  3. #2
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    Alot of jet boats are plumbed with a valve as described. If you want to run a thermostat, use a marine type such as what Rex sells or equiv. Plumbing is more involved using a thermostat. Running injected headers or logs?

    As far as the alternator, depends on what type and how its wired. Most alternators are built with internal regulator and uses a 3 wire hookup. Make wiring simple and convert alternator to a one wire system. If running an amp gauge, convert to a volt gauge. If the engine is covered, make sure its a marine rated alternator.

    Have fun with your new jet boat!

  4. #3
    Positive Vibration Dread Pirate of Humboldt's Avatar
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    You don't need or want a thermostat. Tom at Jet Boat Performance has some easy to read diagrams of how a boat should be plumbed. A pressure relief valve with a bypass is a nice touch though. Have fun with your boat. Look through the jet boat pics section and check out how others have plumbed and rigged their boats.

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  6. #4
    83 Crusader - 468 BBC SNiC's Avatar
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    Thanks Boatless!

    Yes, I am running injected Rewards.
    Does this change things?
    When you say, "plumbing is more involved" with a thermostat, please explain.....

    Here is what I have....
    Inlet water line from pump is split to feed engine under heads.
    Top of Thermostat housing has 3 outlets. One feed to the Rewarders (with a ball check valve and "T") and one to exit line which runs to the stern.
    the third outlet is plugged.

    Am I good to go with installing the missing thermostat?

  7. #5
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    Thanks DP!
    Much appreciated

  8. #6
    Positive Vibration Dread Pirate of Humboldt's Avatar
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    Some boats are set up with thermostats. Rex has a cool setup, but unless you're in really cold water it's unnecessary for most engines. Too much water pressure will pop the intake gasket. That's where the valve and pressure relief come in. What kind of boat did you get and where do you boat?

  9. #7
    83 Crusader - 468 BBC SNiC's Avatar
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    I have an 18 ft 84 Eagle. Pretty nice looking ride....will post pics later.
    I will be riding in Alabama so cold water not an issue.

    My current plumbing setup is;

    Inlet from pump to "hand valve"...split T to heads.
    Thermo cover cap has 3 outlets...
    One is split with a T w/chk valve which feed Rewarders
    One is simply the exit over board line
    One is plugged.

    Do I need a pressure relief with this setup?
    Last edited by SNiC; 04-16-2011 at 09:12 AM.

  10. #8
    83 Crusader - 468 BBC SNiC's Avatar
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    Coupel of pics...




  11. #9
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    Your plumbing description sounds pretty typical, pressure relief needed...nay. If the inlet gate valve @ the pump is wide open and the motor is running to warm, the dump lines are too small, increasing block water pressure.

    You have two problems:

    1) controlling engine temp.

    Idle temp will be different than the running temp, even with the thermostat

    2) controlling the amount of water going thru the headers and the rpm inwhich water is injected into the headers. Headers should run dry @ idle.

    Here's a link to the Bassett website for plumbing and header operation:

    Bassett Racing FAQ

    All my boats used this set-up and worked great.

    The previous owner gutted the thermostat housing for a reason!

    Nice boat!

  12. #10
    Senior Member bp298's Avatar
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    Quote Originally Posted by SNiC View Post
    Do I need a pressure relief with this setup?
    since you're new.

    the discharge port at the pump is tapped to the discharge side of the impeller. at wide open throttle, pressure at that port could exceed 100psig. on some boats, 250psig or higher - depends on several factors. the point is, if you have a thermostat installed at the engine outlet, you can easily achieve very high pressures in the cooling passages. which is why people regulate the water inlet and keep the outlet free flowing.

    next, think about it. this is not a car with a closed cooling system. it is a boat, taking lake temp water, running it through the engine and then overboard. consequently, WATER temperature is not necessarily indicative of ENGINE temperature. oil temps can run 80-100 degrees higher than outlet water temps. i like to see 140, absolutely no more than 150 F* max at the end of a pass. it doesn't bother me to see 130. with a single pass system using cool lake water for cooling, it takes very little flow rate to maintain adequate cooling.

    something else to consider. at wot, the pump is discharging max pressure. with the valve set, flow through the valve correlates to pressure. AT IDLE, pump pressure will be somewhere between 3-10 psig, depending on how low the idle is set in the water with the pump full. because pressure is so low, you will get much less water flow through the engine at idle than you will at cruise or wot.

    i would rather get the engine nice and warm, set the valve to be able to run it for a bit. then actually adjust the thing so the water temps at idle don't exceed 170-175. if you start getting too close to 200-212 in an unpressurized cooling system, you'll risk creation of hotspots in the highest temperature areas of the engine, which can result in engine damage.

    there should be a basset T valve down stream from the outlet going to the headers. this T should close and prevent flow of water to the headers at a preset pressure that coincides with 1500 rpm or so. there should also be weep holes in the bottom loops of the headers, to allow them to drain. make sure the weep holes are open. the reason for the rpm limit, and the weep holes, is to prevent water from accumulating in the loops, and hopefully prevent water reversion back into the engine when it is idling.

    if you're tempted to hook a hose up to the cooling system and start the thing on the trailer, make sure the bow is up - the same "attitude" it would be if it was sitting on the water.

    as far as the alternator, it's very difficult to know what's going on without looking at the boat. some boats were rigged with single wire alternators, some have remote voltage regulators. if it were mine, i wouldn't run it until that problem is FIXED. not "i think it's ok", IS fixed... get a number off the alternator, try to find out what it is for, what the application is, then figure out if that application can work for you.

    then go have some fun with it...

  13. #11
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    The requirement of the diode is not the alternators fault, MSD and some other ignitions have such a low threshhold turn on voltage that the diode is required to keep the coast down alternator voltage from keeping the unit turned on when the key is shut off. That is a design fault of the ignition, in the 40 years that MSD has been manufacturing their unit you would think that they could have incorporated a 20 cent diode in the turn on circuit. Any car will run fine with the diode even if its not needed with a normal output alternator. They could have also incorporated a higher turn on voltage with the addition of a simple, also 20 cent voltage divider, making that problem also go away, but they haven't.
    If you try to regulate the engine temp by restricting the water flow, you will crack the heads at the exhaust seats, and possibly have a hardened seat fall out with catastrophic results. When the engine is run hard and shut off, the water quickly drains from the engine, leaving the exhaust area of the head hot, then when you decide to start the engine back up while it is still hot and light it off to chase someone or pull a skier, the heads are hot, you are at full throttle, and you can be about a block down the lake at full throttle before water fills the heads. And that would be cold lake water. Every time this happens, it cracks just a little more. We can always tell when boat heads are brought in for service, when Magnafluxed, many small exhaust seat cracks are found, and sooner or later they turn into large cracks. I have seen more nice heads turned into junk this way than any other. Lower HP motors have fewer problems, as do lucky people. You may get 3-5 years setup this way, and we have seen others have seats fall out in a few months. Your choice. TIMINATOR
    MODESTY IS A CRUTCH FOR THE INCOMPETENT!

  14. #12
    83 Crusader - 468 BBC SNiC's Avatar
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    Default defining rusetedi

    To all who responded:
    TIMINATOR, bp298, Boatless2

    Thanks Guys!

    This is exactly what I hoped this forum would provide.

    TIMINATOR
    The requirement of the diode is not the alternators fault, MSD and some other ignitions have such a low threshhold turn on voltage that the diode is required to keep the coast down alternator voltage from keeping the unit turned on when the key is shut off.
    Any idea as to why the gauges all went "funky", jumping all over the place when the alt was changed out. To me this would indicate dirty DC line voltage, possibly unregulated. Any thoughts are appreciated!
    I like the idea of converting from a 3 line to a 1 line alt.

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    Junior Member maznfox's Avatar
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    Were in Alabama you located

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    Quote Originally Posted by SNiC View Post
    To all who responded:
    TIMINATOR, bp298, Boatless2

    Thanks Guys!

    This is exactly what I hoped this forum would provide.

    TIMINATORAny idea as to why the gauges all went "funky", jumping all over the place when the alt was changed out. To me this would indicate dirty DC line voltage, possibly unregulated. Any thoughts are appreciated!
    I like the idea of converting from a 3 line to a 1 line alt.
    You may want to check out www.dbelectrical.com for 1-wire alternators and mini starters. They don't have the reverse wound rear mount starters but can't beat their price and warranty. Used both on several engines. They have Marine for closed engine compartments also.

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