Replacement thermostat

BrianN15BrianN15 Member Posts: 25 ✭
in General Boating Discussions
I believe I need to replace a thermostat for my 2003 342 fiesta vee.  5.7 bravo III mercruiser engine.  Trying to find a part number.  Does anybody have any information?
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  • PickleRickPickleRick Member Posts: 4,038 ✭✭✭✭✭


    Engine serial number?

    With that i can punch it into the parts look up and link you to it. Youll also want a gasket.
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  • raybo3raybo3 Administrator Posts: 5,508 admin
    Why do you think you need a t-stat? I have a 2002 and never have changed one. What symptoms are you having?
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org     raybo3@live.com
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  • BrianN15BrianN15 Member Posts: 25 ✭
    Well today I just pulled out a sea water strainer full of sand.  So obviously the raw water supply was less than perfect , causing an overheating issue.  Which did resolve its once while out on water.  Made me think a thermostat was stuck open.  However after find the strainer completely full of sand now I am thinking differently.  After cleaning the strainer ran out to the beach fine this morning.  However after departing back to dock at end of the day I started to get a high temp reading again.  Checked the strainer when docked and the strainer was clear this time.  Is it possible more obstructions could have made their way past the strainer and stuck somewhere in the engine?  It seems to be happening after making some sort of reverse maneuver.  Any thoughts would be so much appreciated
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  • Black_DiamondBlack_Diamond Member Posts: 5,439 ✭✭✭✭✭
    Thermostat is a pretty easy change. I drill a 1/32” hole in the flange to let trapped air escape too. 

    You could well have loaded up the block, power steering cooler and/or the fuel cooler too with sand. A guy by me did that years ago with his diesels. Had to pull them out, strip down and flush the blocks. 😬

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • raybo3raybo3 Administrator Posts: 5,508 admin
    Are you raw water cooled or fresh water? If you're fresh try taking the end caps off your heat exchanger and clean it out. You will be surprised at how little can cause over heating
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org     raybo3@live.com
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  • YYZRCYYZRC Member Posts: 5,140 ✭✭✭✭✭
    raybo3 said:
    Are you raw water cooled or fresh water? If you're fresh try taking the end caps off your heat exchanger and clean it out. You will be surprised at how little can cause over heating
    How do you get the caps off?  I removed the bolt and tried to go further but they seemed to be well stuck on there.
    2008 350 EC on Georgian Bay
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  • Dream_InnDream_Inn Member, Moderator Posts: 7,671 mod
    Any chance @raybo3 you can show us this in more detail?  I have never done it but looked at it once and thought about it but didn't want to mess anything up.

    Dream 'Inn III -- 2008 400 Express

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  • raybo3raybo3 Administrator Posts: 5,508 admin
    On each end of your exchanger there is a bolt (I think its 9/16"). Just take the bolts off and gently pry off the end caps. There is a rubber gasket that I have never changed. Just be careful not to rip it. Once the caps are off I clean whatever I can with my fingers then take the shore water hose and just blast one side and out the other. If its plugged real bad you can use a coat hanger and run it in the "rods" but I never had to do that. Hope this helps. BTW the whole thing should take about 10 minutes per unit.
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org     raybo3@live.com
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  • raybo3raybo3 Administrator Posts: 5,508 admin
    Found this on Youtube. This will give you an idea on how the ends come off. You will most likely not find all the crap in yours. It only takes a very little grass, shells to cause a problem. Remember you can reuse your gaskets as long as you don't rip them.
    https://www.youtube.com/watch?v=ILlniRuI7QE
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org     raybo3@live.com
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  • YYZRCYYZRC Member Posts: 5,140 ✭✭✭✭✭
    raybo3 said:
    Found this on Youtube. This will give you an idea on how the ends come off. You will most likely not find all the crap in yours. It only takes a very little grass, shells to cause a problem. Remember you can reuse your gaskets as long as you don't rip them.
    https://www.youtube.com/watch?v=ILlniRuI7QE
    Wow!!
    2008 350 EC on Georgian Bay
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  • BrianN15BrianN15 Member Posts: 25 ✭
    Black_Diamond said:
    Thermostat is a pretty easy change. I drill a 1/32” hole in the flange to let trapped air escape too. 

    You could well have loaded up the block, power steering cooler and/or the fuel cooler too with sand. A guy by me did that years ago with his diesels. Had to pull them out, strip down and flush the blocks. 😬
     Oh lord Jesus, please don't say that! I can't deal with all that!
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  • BrianN15BrianN15 Member Posts: 25 ✭
    I feel like had I loaded up all those components it wouldnt have ran at 170 the second time out to the beach for the 15 minture ride as well as it did.  If I get into the seawater pump this weekend to look at the impeller is there a way to try and flush the system a bit while I'm in there? Like hook up a shorewater hose to the pump output hose say?
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  • reneechris14reneechris14 Member Posts: 3,134 ✭✭✭✭✭
    If you charge the system with pressurized water  you can flood a cylinder the exhaust is what helps the water go over board. 
    2005 Rinker FV342  Pawcatuck river,Ct
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