Cruising RPM/Hull Speed

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JohnEh

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Jun 7, 2004
76
Hunter 36 Baton Rouge
We have a 2004 Hunter 33 with a Yanmar 3YM30. Last year we had a two blade prop and were able to cruise at 3200 RPM and acheive in excess of 7 knots while motoring in calm seas. Then the wind picked up and the engine overheated and we discovered that Yanmar had put a seawater belt on which was an inch too long and that it was slipping at higher rpms. After the belt was changed, because of frequent high winds, we did not ever get an accurate take on this statistic. Now we have a 3 blade prop. Although we still have high winds, we can't seem to achieve more than 6.5 knots and it is overheating at 3,000 rpm. The tach reads in excess of 4000 with max throttle. The manual says that we should be able to run at 3600-3800(max) for 30 minites and 3400 rpm for 9 out of 10 hours. For you that have this same boat and engine, we will appreciate information about the performance of your boat. Thanks, John & Rachel Ehricht Baton Rouge, LA
 
Jun 4, 2004
17
Hunter 41ac Topping, VA
Engine/Hull Speed

John, We recently moved our 2004 Hunter 33 from winter storage to our regular marina. With fresh bottom paint and a clean 3 blade prop driven by the 3YM30 we reached 7.3 on the knot meter and read 7.0 on the GPS. The difference is the tidal current in the river. RPM was around 3500 for almost an hour and we had no cooling issues. Ask me again in October and I may have a different answer ;-) Barry Bear Necessity H33 #128
 
Jan 2, 2005
779
Hunter 35.5 Legend Lake Travis-Austin,TX
Prop specs.

Sounds like your prop specs. changed enough to where you are not able to get the same "drive" from the 3 blade. Pitch is probably off. One rule of thumb for going from 2 to three blade is 1" less diameter and 1-2 degrees less pitch as I remember it. How did you determine what prop to put on?
 
J

John

Alachua/Prop

The three blade prop was installed at the Hunter factory in Alachua.
 
A

Andy

3 blad and 3200-3600 rpm

never had any problems but I only use it in and out of slip/marina and in the duldrums. My only concern is the noise level, at 3500 it feels like hearing protection is required.
 
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