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  1. Default How cold is TOO cold for a raw water cooled 5.7?

    Morning. I've been lurking this forum for quite some time and finally registered. I have been told over and over again that running without a thermostat MAY cause premature engine wear, but on our dock, we run our boats on plane probably 25 hours per year, at the most. It would take an eon or two, I assume to cause long-term engine wear, by running a cool engine on a long-term basis (I assume). I have a Silverton 330 SB (2002), with a Crusader 5.7 MPI, completely RWC. Only the last seven years have been in salt water, and I now flush after every use, as of a month ago.

    My port motor runs at about 100 degrees, although 100 degrees is the lowest number on the gauge, so it could even be lower. The raw water temp in Newport Harbor (CA) is about 58-74 degrees, depending on the season. Are there people out there who run RWC engines this cold and feel okay about it? The engine sounds phenomenal. Some swear by NO thermostat, so they don't have to worry about overheating and don't have to watch their gauges like a hawk. I like that idea as well (A LOT), but my buddy has 5.7 Crusaders as well (FRESH water cooled), and his engines run at 160 with no thermostats, presumably because his coolant doesn't have time to cool down without the thermostat restriction. I, on the other hand, am dealing with a constant flow of new raw water, so I never get any where near normal operating temp. My question is, how cold is TOO cold? I don't mind running inefficiently or wasting a little fuel, but I do NOT want to ruin my engine. 100 degrees (or potentially colder) seems AWFULLY cold, especially since the motor SHOULD run at about 180, and my RWC setup already needs to run a little inefficiently with the 140 thermostat due to the sale issue. Thoughts, please, as to whether 100 degrees is OBSCENELY cold, or whether that's just how it is with a RWC setup and no thermostat? Thanks so much.

    Happy Monday,
    Scott

  2. #2
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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Without a T-stat you will condensate water in the crank case. Lots of water.
    Chris
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    Let the insanity begin.

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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    IMO never run any engine without a thermostat period. Is it going to be fatal i cant say for sure but your pressing your luck running without a thermostat. Raw water temp only matters if your running in real warm water. The thermostat serves two purposes it allows the engine to reach operating temp plus it restricts water flow so heat transfer can occur. How old are the oil coolers? If unknown just replace them as part of PM!
    It takes a nickle to go first class!
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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    If you're so worried about an overheat condition,just install an alarm that goes off if the temp rises too high.
    https://www.defender.com/product.jsp...0085&id=201601

    As to the original question, when the water is too hard to navigate. Frozen, that is.

    Fresh water cooled and raw water cooled are different terms for the same thing. I think you mean your buddy has closed cooling? That is he has a heat exchanger? In that case he must use a thermostat.
    Last edited by o2batsea; 03-19-2018 at 12:56 PM.
    Practicing the ancient art of ren-ching

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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    All marinized liquid cooled engines should be able to operate at OEM temperature. These are typically sent out the door with a thermostat installed!
    As said, running without a thermostat is asking for trouble!

    as a general rule;

    Whether Raw Water cooled or fitted with a Closed Cooling system, river or lake water boats should run at 160-180 degrees.

    Raw Water cooled engines operating in brackish or salt water should not exceed 145 degrees due to salt chrystalization that occurs at/near 143 degrees.

    Engines fitted with a Closed Cooling system, operating in brackish or salt water, can still run at 160-180. The exhaust system (with all working as it should), will run cooler!




    .
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
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    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    more to where I think Chris was going; you will never get hot enough to purge the water that does condense so it will accumulate and wind up in the oil....the fuel efficiency will suffer - from both the extra friction as well as the intake not being warm enough.....and that will add to dilution of the oil....

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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    just my two cents....I am also in southern california salt water, and I am running twin raw water cooled 454 crusaders. I have a really old boat (1976), owned by several previous owners and I have receipts showing the engines have a maintenance history and evidence of rebuilds over the years. I suspect most recent major overhaul was in late 90's.
    I have self maintained my boats for many years and I am paying particular attention to these motors. They run superbly and the oil looked great before I changed the oil and filters recently, so it really looks great now. I start and run my engines at least once a week, whether I am untying or not.
    I do worry about the lifespan of these motors, but I figure if I keep an eye on things and keep them exercised I can get a lot more out of them, with the anticipated manifolds and risers to come.
    My engine temp gages and verified with my ir temp gun, read a bit under 140 fully warmed.

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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Quote Originally Posted by realcaptron View Post
    just my two cents....I am also in southern california salt water, and I am running twin raw water cooled 454 crusaders. I have a really old boat (1976), owned by several previous owners and I have receipts showing the engines have a maintenance history and evidence of rebuilds over the years. I suspect most recent major overhaul was in late 90's.
    I have self maintained my boats for many years and I am paying particular attention to these motors. They run superbly and the oil looked great before I changed the oil and filters recently, so it really looks great now. I start and run my engines at least once a week, whether I am untying or not.
    I do worry about the lifespan of these motors, but I figure if I keep an eye on things and keep them exercised I can get a lot more out of them, with the anticipated manifolds and risers to come.
    My engine temp gages and verified with my ir temp gun, read a bit under 140 fully warmed.
    Unless you are going to untie from the dock and push the engines up while under a load. Do not start them and run them in the slip. You will hang the valves.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Quote Originally Posted by Docksidemarineservices View Post
    Unless you are going to untie from the dock and push the engines up while under a load. Do not start them and run them in the slip. You will hang the valves.
    I gotta say I've never heard that before
    I've been in the habit of keeping my boat engines exercised in the slip for 45 years of numerous boat ownership. So far I havnt experienced that result. I suppose I'm one of those "can't teach an old dog new tricks" old ****s.

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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Quote Originally Posted by Docksidemarineservices View Post
    Unless you are going to untie from the dock and push the engines up while under a load. Do not start them and run them in the slip. You will hang the valves.
    Chris, I have to ask you....... what have you been smoking?
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

  11. Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Thanks, everyone, for the replies. I just sucked it up and put in a 143 thermostat. I'm sick of accumulating moisture. The motors run great. On a somewhat related note, I hate that my gauges bounce all over the place, with the thermostats in there. The gauge creeps up from 140 to 160, as it should, but then shoots up to 200 very quickly, then immediately back down to 160, then it creeps back down to 140. So I guess everything is working perfectly, except for the gauge shooting up to 200. It literally goes from 160 to 200 and back down to 160, all in 20-25 seconds. Seems awfully strange. I'd say the gauge is just inaccurate, since we all know that can be the case. But BOTH engines/gauges do the exact same thing. I'm not really worried about overheating because my infrared thermometer reads 130-160 at the temperature sender, continuously. The valve covers are 120-140 degrees. The block is at 125 or so. And the manifolds and risers are never above 110. Can anyone explain why the temp gauge on both motors act so strange for those few seconds, every time the thermostat closes and the motor heats up? I find it hard to believe that the water temp at the sender is heating 40 degrees and then cooling 40 degrees, all in 20 seconds, but maybe that's what's happening. It's a mystery to me. I'd love to hear some ideas on what, if anything, I should do. The motors sound fantastic. (By the way, I'm RWC in salt water, so the last thing I want is near-boiling water in my engines.) Thanks a bunch!

  12. Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Addendum to my last reply....... The COOLING by 40 degrees in ten seconds is easy to imagine, since the thermostat is opening at that moment. It's the HEATING by 40 degrees in ten seconds (just prior to the thermostat opening) that baffles me.

  13. #13
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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Get a infrared temp gun and take temps of different parts of the engine and see if you get fluxuations? More than likely the sender is going bad. Do you have dual station guages? You need the correct sender for your setup.
    It takes a nickle to go first class!
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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Quote Originally Posted by Debriefing and Cocktails View Post
    Thanks, everyone, for the replies. I just sucked it up and put in a 143 thermostat. I'm sick of accumulating moisture. The motors run great. On a somewhat related note, I hate that my gauges bounce all over the place, with the thermostats in there. The gauge creeps up from 140 to 160, as it should, but then shoots up to 200 very quickly, then immediately back down to 160, then it creeps back down to 140. So I guess everything is working perfectly, except for the gauge shooting up to 200. It literally goes from 160 to 200 and back down to 160, all in 20-25 seconds. Seems awfully strange. I'd say the gauge is just inaccurate, since we all know that can be the case. But BOTH engines/gauges do the exact same thing. I'm not really worried about overheating because my infrared thermometer reads 130-160 at the temperature sender, continuously. The valve covers are 120-140 degrees. The block is at 125 or so. And the manifolds and risers are never above 110. Can anyone explain why the temp gauge on both motors act so strange for those few seconds, every time the thermostat closes and the motor heats up? I find it hard to believe that the water temp at the sender is heating 40 degrees and then cooling 40 degrees, all in 20 seconds, but maybe that's what's happening. It's a mystery to me. I'd love to hear some ideas on what, if anything, I should do. The motors sound fantastic. (By the way, I'm RWC in salt water, so the last thing I want is near-boiling water in my engines.) Thanks a bunch!
    That sounds pretty weird to me (both gauges doing exactly same thing simultaneously). I think I would check wiring to gauges to see if there is a common ground or something that is loose or corroded and somehow driving the temp gauges crazy.

  15. Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Quote Originally Posted by kimcrwbr1 View Post
    Get a infrared temp gun and take temps of different parts of the engine and see if you get fluxuations? More than likely the sender is going bad. Do you have dual station guages? You need the correct sender for your setup.
    I have single station gauges, and I have already taken temps at different parts of the motor, as described above. Everything seems normal. The temp at the sender reads between 130 and 160 with the infrared temp gun. Block is 125. Valve covers are 120-145. Everything seems normal, except BOTH gauges. I can't decide which is more likely, that the water inside the passage at the sender is heating up 40 degrees in ten seconds, or the gauges (or temperature senders) on BOTH engines have the exact same problem.

  16. Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Quote Originally Posted by realcaptron View Post
    That sounds pretty weird to me (both gauges doing exactly same thing simultaneously). I think I would check wiring to gauges to see if there is a common ground or something that is loose or corroded and somehow driving the temp gauges crazy.

    Realcaptron, just to be clear, the gauges aren't doing the same thing simultaneously. They are simply acting in the same strange manner. They are both shooting up from 160 to 200, then immediately back down to 160, around the time each thermostat opens. Thanks.

  17. #17
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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Maybe drill a small hole in the thermostat to allow any air that gets trapped pass thru when the stat is closed?
    It takes a nickle to go first class!
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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Are these raw water cooled engines possible small hole in suction side of the pumps possible restriction in the thru hull port if applicable. Are both engines pulling from the same water intake?
    It takes a nickle to go first class!
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  19. Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Quote Originally Posted by kimcrwbr1 View Post
    Are these raw water cooled engines possible small hole in suction side of the pumps possible restriction in the thru hull port if applicable. Are both engines pulling from the same water intake?
    No, each engine has its own raw water intake. Maybe a small hole in the thermostat will be my solution, if I can't get this figured out. It would be nice to smooth out the temperature changes (if that is, in fact, the issue). But I'd like to keep the ACTUAL temperature of the engine up in the 140-160 range, so that I am able to eliminate any moisture/condensation that occurs. I hesitate to do anything that will keep the engine running cooler than necessary. I've been running at 100 degrees (without thermostats) for a while. I want a proper operating temp going forward, and I'm already stuck down in the 140-160 range due to the salt water cooling.

    I will investigate any restrictions or leaks as well. Thank you for the tip. But I'm guessing that's not it. My exhaust flow is good at all temps, and I see no drips into the bilge below the engines.

  20. #20
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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Are they thru hull intakes? Adding a sea chest with a strainer will allow you to service the raw water intake while on the water. Makes it nice if you have a livewell you can pull filtered water for it also.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  21. Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Quote Originally Posted by kimcrwbr1 View Post
    Are they thru hull intakes? Adding a sea chest with a strainer will allow you to service the raw water intake while on the water. Makes it nice if you have a livewell you can pull filtered water for it also.
    Yes, each engine has its own through-hull raw water intake. And thank you very much for the info.

    I was just looking online and found a direct-mount water temperature gauge that screws right into the engine. I'll disconnect the temperature sender that attaches to the temp gauge on the bridge, insert the direct-mount water temp gauge into that slot, then run the engines for a while. That should, at the very least, verify the ACTUAL temperature of the water that that spot.

  22. #22
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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Quote Originally Posted by RicardoMarine View Post
    Chris, I have to ask you....... what have you been smoking?
    Really Rick? You know what, run your engine in the slip. It's good for business. I'm out. Good luck.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Quote Originally Posted by Docksidemarineservices View Post
    Really Rick? You know what, run your engine in the slip. It's good for business. I'm out. Good luck.
    In the interest of learning, I'm trying to understand the concept of not running the engines in the slip. If you don't start and run them in the slip, how do you perform basic tune-up procedures, check alternator performance, pumps, timing, all else? Would you rather own a boat that sits dead in the water for extended periods or one that is cranked over and idled routinely?

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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    1 Drill one or two holes in the flange on the thermostat. Some Crusader engines must have the holes or they will show the temperature symptoms you describe. The proper part number will come with the holes already in but just about any holes will work, although too large of ones will not enable the engine to warm up at low speeds. One or two at 1/8" should do it. The engine needs some sort of thermostat bypass to allow engine coolant to reach the thermostat when the thermostat is closed and Crusader sometimes relies on the holes. On my boat the starboard side must have the holes, and the port side relies on the water heater as a bypass. In the absence of some other bypass, and without the holes, the coolant in the block does not move and can reach boiling next to the cylinder walls before enough hot water percolates up and reaches the thermostat to open it. Then the temp quickly falls, the thermostat closes and the cycle begins again. You don't want to run this way, particularly since you are putting very cold raw water onto the overheated block and heads (crack!)

    2 As for running with no thermostat, the coolant water pump is designed to operate in a system where the biggest restriction and pressure drop is at the thermostat. Without this the system will have cavitation and violent pressure swings (at least this is true in closed systems and perhaps in yours as well). The racing community, if they wish to eliminate the thermostat for reliability reasons, will replace it with a washer (the hole size determines the flow and the resultant coolant temperature during the race). So there is a way out that still provides the needed back pressure. In your case, where you operate at different speeds, it really makes no sense. It is better to use a thermostat.

    3 As for running at the dock, I have no idea what the problem may be, other than to note that police car engines are usually modified ("police specials") to improve the oiling so they can run for countless hours at idle (that's what those guys actually do!) I doubt this is the case on boat engines.

  25. #25
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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Quote Originally Posted by realcaptron View Post
    In the interest of learning, I'm trying to understand the concept of not running the engines in the slip. If you don't start and run them in the slip, how do you perform basic tune-up procedures, check alternator performance, pumps, timing, all else? Would you rather own a boat that sits dead in the water for extended periods or one that is cranked over and idled routinely?
    Its not the maintenance that is concern, it is the routine startup.....with 10 minutes of idle and the subsequent shutdown. The thought is the engine never gets to/holds normal operating temperature long enough to 'purge' the crankcase of what has accumulated in the oil (water condensing, mostly).

    I would rather operate the boat 2-3 times a week, if possible, at normal load for at least 20 minutes, min.

    The RWC systems need a restriction to ensure adequate pressure in the block for cooling purposes.....in the pre-Y2K models, there used to be a poppet valve(s) in the tstat outlets....I haven't seen a 'newer' outlet in a while...they may still have it or they could be using a restrictor in the outlets.

  26. Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Quote Originally Posted by CaboJohn View Post
    1 Drill one or two holes in the flange on the thermostat. Some Crusader engines must have the holes or they will show the temperature symptoms you describe. The proper part number will come with the holes already in but just about any holes will work, although too large of ones will not enable the engine to warm up at low speeds. One or two at 1/8" should do it. The engine needs some sort of thermostat bypass to allow engine coolant to reach the thermostat when the thermostat is closed and Crusader sometimes relies on the holes. On my boat the starboard side must have the holes, and the port side relies on the water heater as a bypass. In the absence of some other bypass, and without the holes, the coolant in the block does not move and can reach boiling next to the cylinder walls before enough hot water percolates up and reaches the thermostat to open it. Then the temp quickly falls, the thermostat closes and the cycle begins again. You don't want to run this way, particularly since you are putting very cold raw water onto the overheated block and heads (crack!)

    Thanks, CaboJohn. I'll probably drill one very small hole this weekend and see if that smooths out the gauge a bit. The last thing I want to do is watch the gauge shoot up to 200 every two minutes, even if it DOES come right back down, and even if its NOT the actual temperature of the water at the sender. I'd rather see a smooth 130-150 on the gauge any day. That's still hot enough to evaporate moisture. I suppose I could even try a 160 thermostat and drill a slightly larger hole, if I wanted to get aggressive and raise the engine temp a bit. But I'll save that for another time. Baby steps.

  27. #27
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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Is there a chance the thermostat is in backwards?

  28. Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Zero percent chance, but thank you for the thought. Problem solved, actually. Turns out my gauges and temperature senders didn’t match, so I bought some Faria temp senders, and I’m good to go. The gauge still reads about 15 degrees too high at the upper end of the range, but with my 140 thermostats, the gauge never gets above 175, and even when it gets up close to 175 (actual water temp is 155-160), the gauge quickly comes back down to 135-ish as the thermostat opens. So I’m consistently ranging on the gauge beteeen 135 and 175. Actual temps are 130 to 160 with the infrared thermometer.. Close enough! I’m not going to chase an EXACT reading. I fear I will drive myself crazy. What I have now is consistent, and I’m nowhere near overheating range on the gauge, so I’ll take it. Thanks again to everyone for their input — much appreciated.

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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    Do you have a heater on that engine?
    It takes a nickle to go first class!
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    Default Re: How cold is TOO cold for a raw water cooled 5.7?

    There is the theory side, then the actual reality.

    Theory wants hot oil, near 200 deg or so. The crankcase is free breathing, so the oil attracts atmospheric humidity. Hot oil drives that off.
    The bearings and other metal contact surfaces want oil flow. For lubrication and heat transfer. Flow increases with oil temperature. Cold oil doesn't lube well.

    The reality though compromises this. Its hard to get the right oil temperature, when the the coolant temperature is far too low. Salt water cooled engines really make a compromise. But even FWC engines need to cool the exh manifolds after the coolant leaves the engine. We want to limit boiling in there, so the engine exit temp is likely a bit lower than optimum for engine operation.
    That said, play boat engine hours are usually far less than the design life of the engine. For most users, internal engine wear is not an issue.

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