Starboard Engine Overheating Coming Off Plane

aero3113aero3113 Member Posts: 9,036 ✭✭✭✭✭
Last week coming back to the dock I pulled back the throttle levers to idle into our marina and the starboard engine overheated and the alarm sounded. I quickly put it into reverse then idle and shut down. I waited a few seconds restarted it and the temperature went down to normal like nothing happened. I figured it was seaweed or a plastic bag and it came off when I went into reverse.

Today we left to go to our destination, about a 40 minute run. All was good the whole way and temps were fine. Go to power down to get into the marina and it happens again, starboard engine overheated. I did the same procedure and started back up, all was normal again. What do you guys think is going on?
2008 330EC

Comments

  • PickleRickPickleRick Member Posts: 4,005 ✭✭✭✭✭
    edited July 2023
    Doesn't your engine management system have a sophisticated flow readout to tell if each engine is getting enough raw water?  

    You could also swap thermostats between engines to see if a 15 dollar sticky thermostat is causing an intermittent issue.    

    Stuck open might make it run too cool in raw water.  Stuck closed would impede water flow to the likely two small holes on the outside ring of the thermostat. 
  • aero3113aero3113 Member Posts: 9,036 ✭✭✭✭✭
    @PickleRick I don’t have a digital Vessel View system to see water pressure. I was thinking a sticky thermostat but seems too simple…. I just replaced the thermostats this past winter also.
    2008 330EC
  • PickleRickPickleRick Member Posts: 4,005 ✭✭✭✭✭
    I like starting with simple and cheap....I really like when the problem is the simple and cheap.
  • aero3113aero3113 Member Posts: 9,036 ✭✭✭✭✭
    No overheating coming back to the dock tonight 🤷🏻‍♂️.
    2008 330EC
  • LaReaLaRea Member, Moderator Posts: 7,742 mod
    Mine would do exactly the same thing when it was time to change the raw water impeller.  The pump output was strong at high RPM, but weak at low RPM.  
  • captkevincaptkevin Member Posts: 267 ✭✭
    Not sure if it is correct or not but i was told thermostats stick open when they are bad not closed. If thats true you can rule them out.
    2004 232
    2021 Yamaha Fx svho
  • PickleRickPickleRick Member Posts: 4,005 ✭✭✭✭✭
    A thermostat can stick either way.  The corrosion can also make it stick intermittently in either direction although it's more noticable sticking closed as temps skyrocket quickly. 

    Many times when it sticks open you'll fail to reach normal running temps unless under heavy load (like a boat).    Modern vehicles will throw a CEL it the engine isn't reaching proper running temp.   
  • aero3113aero3113 Member Posts: 9,036 ✭✭✭✭✭
    LaRea said:
    Mine would do exactly the same thing when it was time to change the raw water impeller.  The pump output was strong at high RPM, but weak at low RPM.  
    Wouldn’t mine overheat at idle then? It’s runs normal temp at idle.
    2008 330EC
  • LaReaLaRea Member, Moderator Posts: 7,742 mod
    Any flow at all will keep 'em cool at idle because they don't create much heat. 

    I'm not saying I understand it.  It's just an observation:  every time mine did what yours is doing, I'd change the impeller, and the problem would go away.  It never happened on an impeller less than a season old.  
  • rasburyrasbury Member Posts: 8,381 ✭✭✭✭✭
    I like closed cooling ...nothing but coolant in the system other than the heat exchanger. A lot smaller area to check for plugging up or other issues...and the exhaust elbow...
  • PickleRickPickleRick Member Posts: 4,005 ✭✭✭✭✭
    edited August 2023
    It's been a while since I had raw water cooling but at idle on ear muffs I never could get the motor to normal operating temps.  Even increasing the rpm to 1500 to 1700 it would never get warm enough to open the thermostat.


    There are small holes on either side of the thermostat to allow some bypass circulation.   With no load and at idle one could, in theory, run with a stuck thermostat indefinitely so long as you kept it at idle.  





    @LaRea may be onto something about keeping fresh impellers as it would likely flow more water than an impeller that has begun to lose efficiency as it ages.  

    You're getting plenty of flow at high rpms but after you let off the engine is still extremely hot and while you are pumping water it's not enough flow to keep that cast iron cool. 

  • aero3113aero3113 Member Posts: 9,036 ✭✭✭✭✭
    I’m thinking this issue has to do with the elbows being corroded and plugged up. I’m in the process of replacing them, hopefully I won’t see this issue this season.
    2008 330EC
  • aero3113aero3113 Member Posts: 9,036 ✭✭✭✭✭
    @LaRea I’ll be replacing the impellers on both engines as well 👍🏻.
    2008 330EC
  • LaReaLaRea Member, Moderator Posts: 7,742 mod
    Yeah, with obstructions in the elbows, who knows what kind of crazy uneven cooling you'd get.  I hope this will do it for you.
  • rasburyrasbury Member Posts: 8,381 ✭✭✭✭✭
    I feel like I'm an impeller expert as many times I've replaced mine. I also have two water inlets and I avoid running muffs- I don't think the seacock seals right with the suction- burned up the impeller at least 2x if not more. The way that impeller fills the chamber either the veins are there or they are not. What I will add from my experiences is the pump impeller side to side wears the pump housing , especially if you are in an area with lots of sand, well it's like 100 grit paper grooving the housing and losing pressure . Lots of discussions on here about this- I bought kits with ss spacers and the impeller is a 16th" shorter- solved my problem. They wear also but I'm using the original housing at around 350 hours...100 bucks was the last kit I bought.
  • raybo3raybo3 Administrator Posts: 5,497 admin
    Take the end caps off of your heat exchanger and clean it out. 
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org     raybo3@live.com
  • aero3113aero3113 Member Posts: 9,036 ✭✭✭✭✭
    @raybo3 I’m raw water cooled, no heat exchanger installed.
    2008 330EC
  • aero3113aero3113 Member Posts: 9,036 ✭✭✭✭✭
    edited April 17
    Do you guys feel there’s a shelf life for rubber impellers? I have two kits that have been sitting in a plastic tote in my engine room for the past 5 years that are vacuum sealed. I don’t think there’s an issue but I’ve read some people feel otherwise on other forums.
    2008 330EC
  • Aqua_AuraAqua_Aura Member Posts: 2,617 ✭✭✭✭✭
    edited April 17
    If they are sealed not sure what the issue would be. Rubber seems to be deteriorated by UV, water, and excessive heat none of that should happen sealed in a box 🤔. 

    As long as they aren't dried out or crack when pulling on the fins. 
    1997 Bayliner 3988
  • aero3113aero3113 Member Posts: 9,036 ✭✭✭✭✭
  • captkevincaptkevin Member Posts: 267 ✭✭
    Sure they are fine. If you bought new ones there is no way of knowing how long they have been sitting in the box.
    2004 232
    2021 Yamaha Fx svho
  • LaReaLaRea Member, Moderator Posts: 7,742 mod
    If you're sticking to the Merc maintenance schedule, I'd say the risk is pretty low.  
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