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  1. #1

    Default AQD40A RW Cooling Upgrade

    Hi Guys
    I have just bought an AQD40A/280SP in a 25' Ali fishing boat. I have upgraded the RW intake to a short run thru hull pickup and changed to 2 x 70'C thermostats. This has greatly improved it's cooling efficiency (82'C average at 2800rpm, extended run on a 40'C day) but as I am in the NW of Australia the RW comes in at 31'C at this time of the year so it will still get into alarm (90'C+) if I run at high throttle (3200rpm)

    My question for you is - Can I upgrade my RW pump to the much larger diameter unit that is on later models? Such as on the AQAD40A? Is there any other way to upgrade the RW inlet system for greater cooling efficiency?

    TIA

    Tim
    FV Calypso
    Karratha, Western Australia

  2. #2
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    Default Re: AQD40A RW Cooling Upgrade

    When were the coolers on that engine last acid washed?

  3. #3

    Default Re: AQD40A RW Cooling Upgrade

    Not really sure, probably due, do you know a quick and easy way of doing that? The guy I bought it from reckons it'll do 4000rpm, does that sound right to you? I can only get 23knts/3400rpm flat out and it's hitting the stop on the IP. I'm tempted to play with the stopper screw and max fuel as you would on a land based diesel but I'm afraid I'll be pushing an old (but strong) motor too far

  4. #4

    Default Re: AQD40A RW Cooling Upgrade

    I'll be acid washing the RW circuit in situ this week. HCL 50%/water 50% circulate via buckets and a recirc pump with motor running until it stops fizzing. Then flush for 5 minutes on fresh water.

    Fit new oil and air filters, check turbo exhaust vanes for coking up.

    Then go for a nice long run on a hot day Friday. Air temp will be 35'c, water will be 30'c. Up until now I haven't been able to sustain more than 2800 rpm in those conditions as it climbs from 82'c and steady, to 90'c+ and beyond into alarm if I keep it up there.

    Fingers crossed
    Last edited by dadinabarrel; 03-18-2017 at 05:28 AM.

  5. #5

    Default Re: AQD40A RW Cooling Upgrade

    Tracked down the VP sales brochure for the motor/leg 130hp @ 3600rpm so it's running 400rpm short as I can only really get 3200rpm flat out. I'll check the linkages/cable/IP stop
    Last edited by dadinabarrel; 03-18-2017 at 05:29 AM.

  6. #6
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    Default Re: AQD40A RW Cooling Upgrade

    Are the prop and hull perfectly clean? What state is the RW impeller in? Usual suspects for heat in a marine diesel are RW Impeller, clogged HE or Intercooler or oil cooler, or clogged exhaust elbow. Your combination of low rpms and excess heat could also often be caused by dirty hull or running gear or a prop that is too big. How dirty is the air cleaner?

  7. #7

    Default Re: AQD40A RW Cooling Upgrade

    Hull and prop are spotless, RW impeller is new. Gonna do the acid wash and see. I'm pretty sure the exhaust elbow is ok, as when I have it on the hose/running there is plenty of flow out the exhaust. Gonna put a new air/oil/fuel filter in after the wash. Interesting comment about the prop though. It's got the biggest one that'll go on there. How do I know what the correct size is? Will I lose top end performance with a smaller prop?

  8. #8
    Join Date
    Dec 2015
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    maplevalley WA
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    Default Re: AQD40A RW Cooling Upgrade

    Do you have a manual? boatinfo library has a manual. My best guess is you should be running at 3600 rpm at full throttle under a load if you go two inches less pitch it is possible you will gain in overall performance and not be lugging the engine at top speed.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  9. #9

    Default Re: AQD40A RW Cooling Upgrade

    Hey mate, when you mean 2" less pitch, do you mean 2" less diameter? I thought pitch was measured in degrees angle?

  10. #10
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    Default Re: AQD40A RW Cooling Upgrade

    For every one revolution how far will the prop go forward through a brick wall is pitch
    If it was a drill how big a hole would it cut is width
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  11. #11

    Default Re: AQD40A RW Cooling Upgrade

    Sweet, thanks mate :-)

  12. #12
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    Default Re: AQD40A RW Cooling Upgrade

    What size prop are you running? You may want to get a prop that is cupped as well your basically pushing a barge.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  13. #13

    Default Re: AQD40A RW Cooling Upgrade

    Not a barge :-) Name:  Calypso.png
Views: 95
Size:  17.3 KB

  14. #14
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    Default Re: AQD40A RW Cooling Upgrade

    What size prop are you running?
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  15. #15
    Join Date
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    Default Re: AQD40A RW Cooling Upgrade

    The book says 4000 rpm unloaded when the engine gets hot put it in neutral and run it at full throttle and see if it cools down quickly. That tells you it is getting plenty of coolant the governor should hold it at 4000 rpm.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  16. #16

    Default Re: AQD40A RW Cooling Upgrade

    Ok, I'll have it back in the water next week, I'll have a look at that. It still has the wire on the governor so it looks like it's never been tweaked. Can you add to max fuel like on a diesel truck by winding it in a bit? Not sure on the size prop, I'll measure it tomorrow.

  17. #17
    Join Date
    Dec 2015
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    Default Re: AQD40A RW Cooling Upgrade

    The prop should have numbers on it like 14 L 17 14 inch width Left spinning 17 inch pitch.
    I have a 14 L 17 short hub looking for a home if your pushing 120hp at 3600 rpm then yes you need to bring the WOT rpm to 3600 for max performance maybe gain a few knots in speed as well.
    Last edited by kimcrwbr1; 03-19-2017 at 04:14 PM.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  18. #18

    Default Re: AQD40A RW Cooling Upgrade

    Sweet, I'll check it out tomorow

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