[Public-List] Yanmar 30GM30F prop size

[Mike Lehman]

I have a 12x12 RH on my Universal M4-30, but I gave all of my data (Engine 
HP, Power curve, boat length, LWL, displacement, hull type: full keel, 
aperture opening) to Michigan Wheel before buying a new prop and they have a 
software tool that computes the right prop for your boat. The Atomic 4 prop 
is wrong for sure...plus isn't the Yanmar a left-hand prop?




~~~_/)_/)~~ Mike Lehman ~~_/)~~~


-----Original Message----- 
From: Bill Wallace
Sent: Monday, December 02, 2013 5:17 PM
To: John and Robin Churchill ; Alberg 30 Public List -- open to all
Subject: Re: [Public-List] Yanmar 30GM30F prop size

The prop on my boat, Alberg 30 # 626 "Chewan" powered by a 2GM20F is a 
Dynajet 13x12 RH 3 blade.  That is the largest diameter prop which will 
fit - really it should max out at 12", not 13" as it is a bit too close to 
the edge of the aperture.  The prop is a bit too much prop for the engine - 
I'm not getting full RPM range (to 3000 rpm) at hull speed.  I can keep 
pushing it past about 3/4 throttle, but it only goes marginally faster with 
more horses after about 3/4 throttle.  I've run it for hours at 3/4 throttle 
and it seems fine.  The meter claims I'm getting 2100 rpm roughly at full 
throttle/full speed.  I'm going to measure that in the summer against the 
actual propshaft if I can figure out how so I can tell if it is really 
overpropped or the rpm is reading low.  With 50% more horses in the 3gm30f, 
I would probably go with something similar in size to the 13x12 prop, 
assuming you can make it fit.  The 3gm30f will need a 3 bladed prop to
absorb enough power in the given aperture size.

Bill.



On Monday, December 2, 2013 4:58:02 PM, John and Robin Churchill 
<grafpatrick at earthlink.net> wrote:

hello all-
I am helping a friend with an older A30, repowered with a 3GM30F.  Too much 
power IMHO, but she still will not make hull speed so I suspect the old 
underpitched Atomic 30 prop is still in place.  Anyone with practical 
experience with a good prop size?  Thanks.
John Churchill
Sanibel FL
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