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  1. #1
    Petty Officer 3rd Class
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    Default 1975 mercruiser 165 I6 winterizing question

    Hi guys
    I have a 1975 I6 165hp mercruiser engine. I was wondering if there are just the 2 plugs to full to empty the water and to put the antifreeze in. I found one on the block and one on the manifold but have been told there should be 2 on the manifold. just wondering if anyone knows for sure.
    thanks in advance.

  2. #2
    Admiral ziggy's Avatar
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    Default Re: 1975 mercruiser 165 I6 winterizing question

    my 165 L6 has three drain plugs. just like in the book.
    1 on the block
    1 on the manifold
    1 on the down side of the riser

    to introduce the anti freeze, ya need to remove the tstat housing for the block and head. for the manifold, remove the hose from the ft. of the manifold coming from the tstat housing and feed the anti freeze directly into the manifold from that point.

    be sure and ream out the manifold good while draining. i always have a fair amount of rust that is usually enough to plug the drain hole, thus not allowing it to drain completely. i'd ream out the block drain too, but i got one of them t type drain valves on the engine. ya can't get anything past the drain to ream it out with.

    fwiw. i drain into a folgers regular large size coffee can. says 28.7 oz on the label. i get one full can of water out of my manifold, and get 3 almost full coffee cans full out of my block. if i get that amount, i feel i'm pretty much drained out..
    'Lime Time'
    1975 AristoCraft Nineteen
    Mercruiser 165hp (chevy 250 L6), MC-1 drive

  3. #3
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    Default Re: 1975 mercruiser 165 I6 winterizing question

    thanks for the reply, i will look tomorrow at the riser, assuming its not raining the 2 inches that are expected tomorrow.

  4. #4
    Petty Officer 3rd Class
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    Default Re: 1975 mercruiser 165 I6 winterizing question

    sorry to ask, but what do you mean by the downside of the riser? i looked at the aprts breakdown online and i dont know where i should be looking.
    thanks again

  5. #5
    Admiral ziggy's Avatar
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    Default Re: 1975 mercruiser 165 I6 winterizing question

    the riser is the u shaped item w/4 bolts that bolts to the aft end of the manifold. on the aft side of the riser, on the port side is a drain plug, just like the one you have for the manifold itself. remove the plug to drain..

    fwiw, i never get any water out of that drain hole. ream it, still no water. i suspect it's because i'm rwc and anything on the down side of the riser self drains via gravity.. pure speculation though. never any water out of 'mine' is what i find every time though.

    good luck for no rain for ya..

    edit. the aft end of the riser also has a large dia. rubber tube that connects the riser to the exhaust pipe..
    Last edited by ziggy; September 22nd, 2010 at 02:11 PM. Reason: add comment
    'Lime Time'
    1975 AristoCraft Nineteen
    Mercruiser 165hp (chevy 250 L6), MC-1 drive

  6. #6
    Cadet
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    Default Re: 1975 mercruiser 165 I6 winterizing question

    I also have 165 I6 Mercruiser. After removing the hose from the tstat housing, how much antifreeze do I pour into the hose? Until it flows over the riser?
    Thanks so much!!
    Doug

  7. #7
    Admiral ziggy's Avatar
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    Default Re: 1975 mercruiser 165 I6 winterizing question

    personally, i don't pour any into the hose.
    i remove the tstat cover and introduce it via the tstat hole. then remove the one hose to the ft. of the the manifold from the tstat cover. and fill the manifold directly.
    put tstat cover back and reconnect the hoses.

    i'm thinking real hard about just winterizing with air this season. we'll see..
    'Lime Time'
    1975 AristoCraft Nineteen
    Mercruiser 165hp (chevy 250 L6), MC-1 drive

  8. #8
    Cadet
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    Default Re: 1975 mercruiser 165 I6 winterizing question

    I have a 1981 inline 6 165. I didn't know any better, but I do now after reading this thread, but I've always just opened all the drain plugs and left everything empty till Spring with no problems. Maybe I will add anti-freeze this Winter.

    This month I was having firing problems and converted my engine to electronic ignition. Found a great price for a new distributor on ebay.

    I also bought a new exhaust riser on ebay. The water outlets in the down side of the riser had corroded shut and would let only a pin hole stream of water out. She runs cool as can be now.
    The old riser had a drain plug on it, but the new one (made in China) does not. I never got any water out of the old one anyway.

  9. #9
    Seaman Apprentice
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    Default Re: 1975 mercruiser 165 I6 winterizing question

    I always run mine on the muffs, open the stop cocks to make sure they are clean and running, usually have to clean one out, and I like to see clear water coming out. Then shut if off and let and it drain. Been done that way for years, no antifreeze, no problems.
    "FRANKENBOAT"
    1975 Sea Ray SRV 193. 18' open bow inline 6.

  10. #10

    Default Re: 1975 mercruiser 165 I6 winterizing question

    I'm resurrecting this thread as this is my exact engine, I just bought the boat last month, and I need to winterize it tonight (32F tomorrow night). I've got the Clymer manual, so following directions have removed the exhaust manifold drain plug and exhaust elbow drain plug and plenty of water drained so that looks good. The cylinder block petcock isn't a bolt so doesn't look like I remove it. Do I? My main concern is the water distribution block. I removed the cover & pulled the thermostat, disconnected the hose at the manifold front end cap. Where I pulled the thermostat there is water and I don't know how to drain that. What am I missing? With this being my first time I'm nervous about leaving water in an important part of the engine. I am not a gear head, so I'm doubly nervous. I appreciate any help you can give this rookie.

  11. #11
    Chief Petty Officer
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    Default Re: 1975 mercruiser 165 I6 winterizing question

    you should start your own thread and not piggyback onto someone elses.pull the lower hose off the water circulating pump thats the one your belt is driving around.air doesn't freeze so most just remove all traces of water and the drains are generally enough but there are small pockets that can still have a little water but with a majority gone the cooling water has somewhere to expand to rather than an undrained block that is just full and therefore cracking occurs.

  12. #12
    Admiral ziggy's Avatar
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    Default Re: 1975 mercruiser 165 I6 winterizing question

    The cylinder block petcock isn't a bolt so doesn't look like I remove it. Do I?
    no, it's a petcock. ya turn the t ccw to open it. cw to close it. it can't be reamed out. at least not mine.

    the brass looking thing with a t on it at the back bottom port side is the drain point. the petcock.
    Where I pulled the thermostat there is water and I don't know how to drain that. What am I missing?
    the petcock at the bottom back port side of the engine. use that to drain the water out.
    fwiw. i get three folgers coffee cans mostly full when i drain all the water out.. i get one coffee can full from the manifold. one coffee can is 27.8 oz per the label.
    'Lime Time'
    1975 AristoCraft Nineteen
    Mercruiser 165hp (chevy 250 L6), MC-1 drive

  13. #13
    Petty Officer 1st Class kilowatts's Avatar
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    Default Re: 1975 mercruiser 165 I6 winterizing question

    Hi Guys:

    I have the inline 6 and when I winterize I don't use any antifreeze. I have the fresh water cooling system so I only drain the raw water side completely and then leave the plugs out and the passages empty. So far no problems.

    This topic seems to be a bit like the oil topics inasmuch as different people have strong ideas on coolant vs. air. I don't think it makes much difference so long as it works for you. The manual does call for coolant though if I remember it rightly.

    kilowatts

  14. #14

    Default Re: 1975 mercruiser 165 I6 winterizing question

    Thanks so much to all of you who responded today. I apologize for the poor netiquette in piggybacking on a post but was in a bind. I'll create my own posts next time. I look forward to learning a lot more about my boat through the posters on here. Again, thanks. I was able to drain all the water that I could find and I feel much better about the 24-27 degrees it's going to hit each night the next 3 days. Now off to change the oil (next time I'll do that first). - Russ in Montana

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