Hunter 44AC Boat Speed Under Power

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Don12364

Don12364

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Dec 2, 2003
1,637
Hunter 376 Warsash, England --
Marc,
Sorry about the delay in my response but have spent all week sailing aboard 1935 built yacht with no engine nor any electrics. Back to basics and real fun!
Re your drive chain, give me the gearbox info from the small plate on the outside or just the ratio in forward and I will re-run Propcalc for you.
Rgds.
 
Marc14857

Marc14857

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Jun 5, 2004
485
Hunter 44 Mystic, Ct
Donalex

Thanks for offering to re run the propcalc. The forward gear ratio is 2:33. I did inspect the prop last weekend and it did have some significant barnacle growrth which I had a diver clean up. That helped to the tune of about 1/2 to 1 knot as best I can tell but still nowhere near the speeds the other 44 owners can get. I could not verify the prop size though I expect it is an 18 x 13. I've been thinking of getting a folding prop and have narrowed the choice down to a flexofold (They recommend 18 x 14) or a Gori and they feel strongly that the prop should be a 20 x 14. They claim to have installed that size on several 44s with excellent results.
 
Don12364

Don12364

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Dec 2, 2003
1,637
Hunter 376 Warsash, England --
Hi Marc,
Just re-run Propcalc for your boat.
Data used:-
Hull Type = Full Displacement
Waterline Length = 39'2" (39.17')
Displacement = 22,936 lb
Engine = Inboard
Engine BHP = 55 @ 3000 rpm
Gearbox ratio = 2.33:1

Result:-
Max Speed 8.57 Kts = 9.86 mph with Prop Diameter 18.77" & Pitch 15.25"

Caveat:- This is normally a suitable prop but might be improved with fine tuning.

If, like me, every locker is stuffed full of junk and the boat weighs 1000 lb more than Hunters' claimed displacement, then enter a new all up weight 1000 lb more. i.e. = 23936 lb.
Speed drops to 8.45 Kt and the optimum pitch is 15.05".
(BTW - Nobody bothers with fractions of an inch in pitch).

Try it yourself by downloading the free Propcalc prog from Castle Marine - Scroll to foot of page to see the 'Download' button.
http://www.castlemarine.co.uk/pitch.htm
Select "Enter Prop Calculation" and then just enter your details and hit the "View Calculation" tab at top of page

If you are seriously into prop calculations I have an early DOS program I could send you which uses the identical formula but which allows you to enter the details of your prop and gives the speed etc from that. If your prop is only 12" pitch then I would expect the performance which you currently get.

BTW I am not keen on folders because of the lack of "brakes" despite grandiose claims by the makers. A feathering prop not only gives same thrust ahead and astern but also allows adjustment of the pitch so you can fiddle to your heart's content until you get the performance you want.
It hurts in the wallet dept though but I have fitted them to my last two boats with considerable improvements in sailing and reversing.
Rgds,
Don.
 
tkwhalen

tkwhalen

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Jun 8, 2004
283
Hunter 49 60803 Lake Erie
Marc

I have 2004 44AC and motor at speeds similiar to Schatzi. At 2800 I'm around 7.2 to 7.4 open throttle I'm over 7.5. I generally motor around 2600 which is just under 7 Knots of speed when the lake is relatively calm.
 
G

Graysailor

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May 22, 2004
121
Hunter h41 San Francisco
For whatever it is worth. I would stick to what the plate says on the engine. My 2008 h41 also has a rating of 3000rpm. I have found the sweet spot seems to be around 27-2800rpm. Like you I am the slowest boat on the water. 5-6 knots. Also, I do not push my engine to the max. Also, being a live a board my boat is probably somewhat heavier then the week end sailor. I am sure that I have at least 1500-2000 pounds of extra gear on board. AC, Genset, 300 feet of chain rode, spares. It all takes a toll on speed.
 
Marc14857

Marc14857

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Jun 5, 2004
485
Hunter 44 Mystic, Ct
Speed Update

We finally had some good weather to do some more testing. I still have not verified that I have the correct prop however we were motoring today in calm conditions and even though the max RPM on the 4JH4E is 3000 RPM I was able to get the RPMs up to 3800 and there was probably a little more to go but I didn't want to push any harder. Boat speed came up from 5 knots at an indicated 3000 RPM to 7 Knots at an indicated 3800 RPM. Ran this way for a few minites and the engine did not overheat. I'm now wondering if my tach is not very accurate or I suppose I can still have an underpitched prop. We pull the boat in November so I will be able to check the prop and in the meantime I'll be looking for a way to check the true engine RPMs.
 
Don12364

Don12364

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Dec 2, 2003
1,637
Hunter 376 Warsash, England --
Marc14857 said:
in the meantime I'll be looking for a way to check the true engine RPMs.
Click to expand
Marc,
Thanks for the reminder - I just ordered non-contacting laser tacho from e-bay.
£10 UK (approx $12 US) post free from China/Hong Kong. Much easier and safer to use than my contacting tacho.
 
Marc14857

Marc14857

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Jun 5, 2004
485
Hunter 44 Mystic, Ct
We found the problem!

Finally had a chance to check the installed Yanmar tachometer against a hand held unit I just purchased. The Yanmar unit reads consistently and proportionality low. With the Yanmar tach at 3000 RPM the hand held unit was reading about 2200 RPM. The Yanmar read almost 3900 when the hand held read 3000RPM. Again max engine RPM per the nameplate is 3000RPM. I am thinking back to all the motoring I did this year at 4.5 to 5 knots when we could have been up around 7 to 7.5 with the rest of you. Oh well. There is currently another Hunter thread on Yanmar tachs and one 44 owner reported a problem with his tach that was traced back to the alternator smart regulator. I have the same regulator and the upgraded alternator 90 - 100 amp alternator. I wonder if the pulley diameters are different from the standard alternator which would be problematic. In any event I will be looking into getting a new tach sensor off of the fly wheel instead of the alternator.

I want to thank all the owners who helped me out with this issue. Can't tell you all how relieved I am that the engine is OK and how much money I'm going to save not buying a new prop. Unfortunately will have to wait to next year to see the results as we are coming out of the water next week or two.

Marc
 
Vinny

Vinny

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Apr 6, 2006
343
Boat Less New Bern NC
Re: We found the problem!

As I said on the other thread. Your tach may have a calibration screw on the back for an easy fix.
 
Marc14857

Marc14857

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Jun 5, 2004
485
Hunter 44 Mystic, Ct
Finally found out how to calibrate the tach for the 14 pole alternator vs the standard 10 pole alternator. Since the tach gets it's input from the alternator, it must be adjusted to the number of poles on the alternator. Mine was set at 10 when it should have been 14. As such the tach was seeing 14 pulses per alternator RPM but it was calibrated for 10 pulses per engine RPM so it read high all the time. I really never got to the 3000 RPM max engine speed which is why I was never able to motor at speeds that you all were achieving. Almost bought a new tach for $400 . Any of the Yanmar tachs which are manufactured by VDO with built in hour meter are easily programmable. If anyone needs the calibration info E Mail me and I will gladly forward the PDF instructions.
 
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