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  1. #1

    Default 1972 Uniflite Sport Sedan 31 performance issues

    Hello all

    I've been going through the forum about the old Uniflites with Chrysler 318's. It seems that quite a few of you cruise in the high 20's, someone even said he was getting up to 40 mph.

    I bought my boat 2 years ago. One engine overheated and stalled on the way to my new slip. For that entire summer I couldn't bring it over 2000 RPM without it overheating. Through trial and error I replaced the raw water pump, fresh water pump, manifolds, risers, cleaned heat exchanger, new carb and fuel pump.

    Last summer there were no overheating issues. That said, the previous owner kept a fairly comprehensive journal. When they bought the boat 20 years ago they claimed that it would do about 22 knots at 3300 RPM. At that RPM I am lucky to get 17 knots. I usually try to cruise at 2700 RPM and I get about 14 knots.

    I have fuel flow meters, working trim tabs, and my speed I am getting from my GPS.

    Does this sound normal? Others seem to be getting a lot more speed from the same boat. Could the engines just be getting worn out? Should I check the compression? It has an updated point system, it seems like everything is working as it should, just real slow.

    Thanks

  2. #2
    Join Date
    Sep 2008
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    Maryland - USA
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    Default Re: 1972 Uniflite Sport Sedan 31 performance issues

    I doubt the 40 MPH claim is legit....

    I would start by checking the spark advance...if that's not working properly, your engines won't make rated power...

  3. #3

    Default Re: 1972 Uniflite Sport Sedan 31 performance issues

    Thank you for the quick response. Is that just checking the timing? I guess I'd have to use a dwell meter for that?
    The engines are both just under 700 hours and were rebuilt once already

  4. #4
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    Sep 2008
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    Default Re: 1972 Uniflite Sport Sedan 31 performance issues

    it is checking the timing as a function of RPM...and a clip on (inductive) timing light is usually best...

    The Dwell Meter measures the point gap indirectly...and that setting has to be correct before checking the timing.

    Hours really don't matter unless you know for sure that the distributors were overhauled when the engines were rebuild...sad to say but its very likely the distributors didn't get anything more than a set of points, the condenser, a rotor and a new cap...

  5. #5
    Join Date
    Dec 2006
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    Greenfield Me. USA
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    6,237

    Default Re: 1972 Uniflite Sport Sedan 31 performance issues

    Ayuh,..... How long has this hull been in the water,..??
    How long has it been since the bottom was cleaned,..??
    Any Grease is Better,... Than No grease at All....

  6. #6
    Join Date
    May 2010
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    DC Burbs/Maryland Eastern Shore
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    2,312

    Default Re: 1972 Uniflite Sport Sedan 31 performance issues

    Keys to speed (if that's your goal) are clean hull with fresh paint, tuned propellers, properly functioning engine and transmission, and unloading unnecessary weight. If you have made certain of all those factors and still have difficulty making speed then it must be something radically wrong somewhere.
    Practicing the ancient art of ren-ching

  7. #7

    Default Re: 1972 Uniflite Sport Sedan 31 performance issues

    Thanks for the responses guys. I boat in the Pacific North West. Ocean boating, but I keep the boat in a boathouse on a river, so the water is brackish.
    I pull it out every year and clean the hull and add a new coat of anti-fouling.
    Its just my wife and I on the boat, it is fairly well balanced.
    I don't mind going slow, its just that if I'm only doing 14knots but am supposed to be doing 22 at the same RPM I'd like to figure out why. If I can make it to my destination 80% quicker for the same amount of fuel that would be amazing!
    Aft of one engine is the starting battery, aft of the other is the holding tank, so there is very little room for a timing light, or is there another place to aim it?
    I've attached a photo of the engine room.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  8. #8
    Join Date
    Sep 2010
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    Jersey Shore
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    Default Re: 1972 Uniflite Sport Sedan 31 performance issues

    So, how much paint is on the hull?
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  9. #9
    Join Date
    May 2010
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    DC Burbs/Maryland Eastern Shore
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    Default Re: 1972 Uniflite Sport Sedan 31 performance issues

    Uni's are heavy boats. They're way overbuilt, which is good, but using those two tired-out Mopars to push it is asking a lot. I think you're about at the edge of your performance envelope with those ponies.
    No way that boat has ever seen 40 mph or even 30.
    Last edited by o2batsea; 12-20-2021 at 10:36 AM.
    Practicing the ancient art of ren-ching

  10. #10
    Join Date
    May 2010
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    Default Re: 1972 Uniflite Sport Sedan 31 performance issues

    If you REALLY LOVE this thing and plan to keep it until you are buried at sea, then consider a pair of big blocks. You have the room for them and they can turn a fatter wheel than what you have. This will wake that thing up. Your fuel costs will go through the roof but you'll certainly be able to get there in less time.
    I am a cheap fart, so I would probably send out the heads for reconditioning, put in a new camshaft/lifters, full tune up kit and be happy with life in the slow lane. I'd have a real close look at the lump that overheated to see if the rings scored the bores or some other dismal failure occurred.
    Practicing the ancient art of ren-ching

  11. #11
    Join Date
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    Default Re: 1972 Uniflite Sport Sedan 31 performance issues

    Slower speeds than before with the same RPM has nothing to do with performance.... Something has changed with the hull/props/load.

    If the bottom has not been blasted in the 50 years this hull has been in service, even 15 years... that is a lot of weight in paint. About 4 knots worth.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  12. #12

    Default Re: 1972 Uniflite Sport Sedan 31 performance issues

    Maybe ill try grinding off the paint below the water line and doing a repaint next year. I'll also budget for a tune up/.rebuild. It is running fine, just seems slow. I'll do the timing right away and see if that helps at all.

    Thanks for the input guys.Click image for larger version. 

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  13. #13
    Join Date
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    Default Re: 1972 Uniflite Sport Sedan 31 performance issues

    Quote Originally Posted by dssbodhi View Post
    Maybe ill try grinding off the paint below the water line and doing a repaint next year. I'll also budget for a tune up/.rebuild. It is running fine, just seems slow. I'll do the timing right away and see if that helps at all.

    Thanks for the input guys.Click image for larger version. 

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    Get a price on having it blasted and barrier coated.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

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