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  1. #1
    Lieutenant Junior Grade eavega's Avatar
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    Default Mercruiser 470 3" vs 4" Heat Exchanger

    So, I am looking at a boat that has the dreaded Mercruiser 470 170 HP motor. I keep reading that the main problems it has is the stator/rectifier which is resolved with adding a real alternator, potential coolant leak necessitating re-sleeving and re-sealing camshaft, and possible overheats with the 3" heat exchanger. Per the seller, the motor has had the alternator mod installed, and does not have any coolant leaks (but cannot say if the seals have been replaced at any point). He is not near the boat (Lake House) but does not know if it has the 3" or 4" Heat Exchanger. He can say that he has not had any overheat issues with the boat in the two years he has owned it, nor any loss of compression.
    Everything I read about the heat exchanger mentions "Later models" have the 4" HE. Does anyone know when they switched over to the 4" HE? I am not that concerned since the owner and his mechanic (whom I spoke to) says that the motor has not had any overheat issues, at least in the two years they have owned and serviced the boat. I do, however, want to know if it is something I need to consider in the future.
    Any information that can be provided would be greatly appreciated.

    Rgds

    1988 Stingray 176 SVB with Mercruiser 3.0L (181 CID) - The Ghostrider

  2. #2
    Commander Eric 3.7LX Alpha 1's Avatar
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    Default Re: Mercruiser 470 3" vs 4" Heat Exchanger

    I don't know the exact year, but is easy to tell when you go look at the boat...

    The exchanger is on the port side of the engine, (same side and just above the starter), and you can measure the diameter of it easily.

    I have an '89 which was the last year they were made... I have the 4"

  3. #3
    Petty Officer 2nd Class
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    Default Re: Mercruiser 470 3" vs 4" Heat Exchanger

    Ours is an 88 3.7l w a 4" HE, might be a help for ya.

  4. #4
    Lieutenant Junior Grade eavega's Avatar
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    Default Re: Mercruiser 470 3" vs 4" Heat Exchanger

    Thanks for the replies. I went to check out the boat today, and was not happy with what I saw. Motor-wise, the boat did have the 4" heat exchanger, but still had the points ignition. The boat itself was not in the best condition, so I took a pass. Oddly enough, I did go on a lark to see a more recent model of the same boat which had the Mercruiser 3.0l engine, and took that one home.

    Rgds

    1988 Stingray 176 SVB with Mercruiser 3.0L (181 CID) - The Ghostrider

  5. #5
    Chief Petty Officer
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    Default Re: Mercruiser 470 3" vs 4" Heat Exchanger

    Quote Originally Posted by eavega View Post
    Thanks for the replies. I went to check out the boat today, and was not happy with what I saw. Motor-wise, the boat did have the 4" heat exchanger, but still had the points ignition. The boat itself was not in the best condition, so I took a pass. Oddly enough, I did go on a lark to see a more recent model of the same boat which had the Mercruiser 3.0l engine, and took that one home.

    Rgds
    i know you didn't buy the boat i think from other post they started to use 4" exchangers on the 470's in 82

  6. #6

    Default Re: Mercruiser 470 3" vs 4" Heat Exchanger

    Mine is a '77 SC Tristar and has the 3". No overheating issues other than a slight rise in temp when tubing so I may go ahead and change it anyway just in case. Know of any good places I can get one?

  7. #7
    Lieutenant Junior Grade eavega's Avatar
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    Default Re: Mercruiser 470 3" vs 4" Heat Exchanger

    Quote Originally Posted by Noie View Post
    Mine is a '77 SC Tristar and has the 3". No overheating issues other than a slight rise in temp when tubing so I may go ahead and change it anyway just in case. Know of any good places I can get one?
    I saw a couple of places online that sell the larger heat exchanger. The price was unattractive.

    Rgds

    1988 Stingray 176 SVB with Mercruiser 3.0L (181 CID) - The Ghostrider

  8. #8
    Chief Petty Officer
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    Default Re: Mercruiser 470 3" vs 4" Heat Exchanger

    Quote Originally Posted by Noie View Post
    Mine is a '77 SC Tristar and has the 3". No overheating issues other than a slight rise in temp when tubing so I may go ahead and change it anyway just in case. Know of any good places I can get one?
    if your boat is not overheating then don't worry about the 3" if the temp rises tubing just beaware of it and when the temp goes up just give it a rest and then have fun again but you also have to beaware of the water temp if the water is colder then you should have no worries but if the water is warm through mid summer then the temp will rise even with a 4". the only time you will start having trouble is when the 3" starts to break down and start clogging it's self

  9. #9

    Default Re: Mercruiser 470 3" vs 4" Heat Exchanger

    Guess it makes sense just to leave it and monitor. With this 470 I'm sure I'll find something to spend the saved money on!

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