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Thread: 8.1L Marine Power Overheating

  1. #1
    Member orion94us's Avatar
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    Default 8.1L Marine Power Overheating

    I've got an 8.1 L throttle bod injected Marine Power with 212 pump on my North River Commander. I've been having issues with it overheating at low RPMS. It did it to me in Seward last week as I was leaving the Harbor. I had just got to the outside buoys from the back boat launch when my alarm went off. it did again today motoring around a local lake. Antifreeze level seems ok. No leaks that I can see from anywhere.

    If I run on step, it stays cool in normal operating range.

    Anyone have any ideas or ran into this issue? Motor only has 200 hrs on it.

    Thank you in advance

    Chris

  2. #2
    Member Music Man's Avatar
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    Check heat exchanger, might be partially clogged especially if you don't have a sand trap.
    When seconds count, the cops are just minutes away.
    '08 24' HCM Granite HD "River Dog"

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    Quote Originally Posted by Music Man View Post
    Check heat exchanger, might be partially clogged especially if you don't have a sand trap.
    That would be the long cylindrical metal tube with what look like brass rods inside it correct? Also where the direct fill for the coolant goes? Sorry I'm new to jet boats.


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    Member Music Man's Avatar
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    You are correct. The brass rods are tubes that the cold raw water flows through , so if some are clogged up you will overheat.
    When seconds count, the cops are just minutes away.
    '08 24' HCM Granite HD "River Dog"

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    Quote Originally Posted by Music Man View Post
    You are correct. The brass rods are tubes that the cold raw water flows through , so if some are clogged up you will overheat.
    Ok. Like a boiler system. Thank you for the information. I'll do the Google thing and see if I can figure out how to open it up and flush them out.


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    Well I cleaned the tubes in the heat exchanger. Didn't see any sign of blockage or build up in them. For what it's worth, a .17 caliber brush fits perfect inside the tubes lol. Back flushed the intake system from the heat exchanger out. Didn't see any obvious debris there either. Any other places to check? Hoping to get it back on the water this weekend to see if she's cured of her hot flashes....

    Chris


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    Member Music Man's Avatar
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    Change the thermostat because they are cheap. If still overheating check for obstruction in freshwater line to and from heat exchanger. Cap
    When seconds count, the cops are just minutes away.
    '08 24' HCM Granite HD "River Dog"

  8. #8

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    I have an inboard and don't know squat about jets, but on an inboard if the impeller inside the water pump needs replacement (because the vanes no longer "stick out" like they did when the impeller was new), then the engine will heat up at low rpms and be fine at higher rpms because it's spinning faster and moving more water through the engine.

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    Member Music Man's Avatar
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    No pump like you are thinking. In a closed system the water pomp is just like in your car and the jet pump forces the raw water through the heat exchanger to do the cooling.
    When seconds count, the cops are just minutes away.
    '08 24' HCM Granite HD "River Dog"

  10. #10

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    About the only time that you need to replace a water pump on a inboard is when the seals go out and it starts leaking out through the weep hole on the bottom front of the pump.


    Quote Originally Posted by skydiver View Post
    I have an inboard and don't know squat about jets, but on an inboard if the impeller inside the water pump needs replacement (because the vanes no longer "stick out" like they did when the impeller was new), then the engine will heat up at low rpms and be fine at higher rpms because it's spinning faster and moving more water through the engine.
    Last edited by Big Bend; 08-09-2016 at 13:02. Reason: Spelling

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    Is the water pump driven by a belt if so check to see if it loose.

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    Belt seems to be tight. Currently running around Kenai and Soldotna trying to find a thermostat for it.


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    I have a Marine Power 6.0L that I installed in 2008. I ahead the same problem, the engine would overheat at low rpm's. Installed two new radiator caps with no luck. I finally ordered a new heat exchanger (paid for and should have been under warranty) and that fixed the problem. After the problem was fixed I sent the bad one back to Marine Power for evaluation and they determined it was a manufacturing error and credited my account. It was two very frustrating months before the issue was resolved.

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    I'm starting to really regret buying a marine power engine. I can't find a part # for the right thermostat. Can not even find a working # for Marine Power to call them direct. I sure hope something like my water pump doesn't go out !!!!


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    I feel your pain. Nothing is more frustrating than to buy a new motor and expecting it to work. I purchased my Marine Power from an Alaska vendor that was not much help. Try to contact George Fowler at Marine Power he has been very helpful and gets parts out in a timely manner. Once I had everything smoothed out I have been very happy with the performance of my Marine Power engine. Installed my engine in 2008 and just this year I had to replace a fuel pump.

    George Fowler
    gfowler@marinepowerusa.com
    (985) 386-2081

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    Quote Originally Posted by Rod123 View Post
    I feel your pain. Nothing is more frustrating than to buy a new motor and expecting it to work. I purchased my Marine Power from an Alaska vendor that was not much help. Try to contact George Fowler at Marine Power he has been very helpful and gets parts out in a timely manner. Once I had everything smoothed out I have been very happy with the performance of my Marine Power engine. Installed my engine in 2008 and just this year I had to replace a fuel pump.

    George Fowler
    gfowler@marinepowerusa.com
    (985) 386-2081
    Thank you for the number. I will call him first thing in the morning!

    Chris


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    Quote Originally Posted by Rod123 View Post
    I feel your pain. Nothing is more frustrating than to buy a new motor and expecting it to work. I purchased my Marine Power from an Alaska vendor that was not much help. Try to contact George Fowler at Marine Power he has been very helpful and gets parts out in a timely manner. Once I had everything smoothed out I have been very happy with the performance of my Marine Power engine. Installed my engine in 2008 and just this year I had to replace a fuel pump.

    George Fowler
    gfowler@marinepowerusa.com
    (985) 386-2081
    Got George on the phone today. Super nice guy, very helpful!!! He took the time to walk me through the raw water system and told me some other common causes as well as how to diagnose and if necessary fix. Very positive experience to say the least!

    Chris


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    Chris,

    I am glad George was helpful, he certainly has been good for me. I hope it all works out.

    Rod

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    Quote Originally Posted by Rod123 View Post
    Chris,

    I am glad George was helpful, he certainly has been good for me. I hope it all works out.

    Rod
    I think I figured out where the issue lay. After double checking the exhaust risers to make sure I wasn't losing coolant out my exhaust, installing a new thermostat, and having the heat exchanger pressure tested, the problem showed itself. There is a rubber o-ring that mates the heat exchanger to the thermostat riser. I had a pinhole sized leak down the back side of that riser that ran straight to the engine. The coolant would leak slowly enough that unless you were looking at the back side of the riser you would not see it seeping, then burn off on the engine when it was warm and under power. With the dog house closed and running a guy would never smell the coolant being burned offf as it would vent straight out the back of the boat. Installed a new o ring, fixed right?... wrong..... Still did not seal correctly. So I determined that my heat exchanger was slightly out of round. I bought some cork gasket material, and made an extra gasket to put in between the o ring and heat exchanger, then cut a piece of siphon hose in half and added that under the top retention strap that holds down the heat exchanger, refilled and VOILA!!! No more leaking and no more overheating. Took the boat out for a day of Halibut fishing in Homer last week and didn't lose any coolant or get warm motoring out of the harbor.

    Just wanted to throw this out there in case anyone has a similar issue and it's not something blaringly obvious.

    Thank you all for the insight and help!

    Chris

    PS. George was very helpful through the entire process, even though they were displaced due to flooding down there in Louisiana.

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