There are at least 3 Yanmar 2QM15 installed in Alberg 30's. The ones I know of were installed by Chris Oliver (Annapolis) in the early'80's. See Qm15Specifications. Also here is a short list of cross referenced Qm15Parts.
1. The wheel (propeller) on my boat is a Michigan sailor 13X12RH. The combination provides profoundly more thrust than the A4 original
2. The original mounts are not robust enough. Yanmar makes an upgrade for them
3. Oliver installed a special Marine filter as the primary fuel filter. That is a gas filter and not suitable for diesel. Racor filter is what you want.
4. Backing down when aground from gunkholing is almost always successful-a non event with the A4. The down side is a. watch your dingy painter. The wheel will suck it in (a lesson from the school of hard knocks)b. pieces of shell and other debris from the bottom will get sucked into the raw water intake, and then 'shell' the water impeller. A Groco basket type water strainer is well worth the investment.
Shaft & Prop
From: "sousa, stephen4AGg</ENG)" <email@example.com>
The measurement for the shaft from #114 is 7/8 in diameter X 29 1/2 inches long. I am not sure if this will fit with the 3gm, I have the 2gm which has a shorter block. The actual length would depend on your the bed and placement of the motor.
If the installation is from a gas to diesel the pitch for the prop may change due to the power curve. I am running a 13 X 13 sail pitch and have excellent performance. You will love the Yanmar, excellent fuel economy and starts in all type of cold temperture conditions. I would also recommend 15W40 Chevron Delo 400 which I run in the Yanmar and my Cummins, great all around oil and is available at Walmart.
Prop-Sizing: Yanmar vs. Atomic 4
From: "Mike Lehman" <firstname.lastname@example.org>
The Atomic 4 is 1:1 so 1500 engine RPM is 1500 prop RPM. Most small diesels have a reduction gear something like 2:1 so the engine will run at 2800 RPM for the same prop rotation. You need to check the specs on your engine. The prop should be sized and pitched for the performance curve of your particular engine. The Atomic 4 prop will not be the ideal prop for your diesel, but will drive the boat.
Michigan Wheel has an excellent service and website for matching the boat/engine/prop. This is not guess work, it is very precise.
Mike Lehman ><((((º>¸.·´¯`·...¸><((((º>
From: George Dinwiddie <email@example.com>
The Atomic 4 has a 1:1 drive. All the diesels are geared down, and require more pitch in the prop than the Atomic 4. You can get the prop shop to calculate for you, but most people seem to end up with a 13x13 or a 13x12 (or maybe a 12").
- - George
From: "Michael" <firstname.lastname@example.org>
>I also have a prop question; my A30 has a Yanmar 3GM30 with2:61 gear; I was >told that a 12x10R 3 blade was appropriate
That's a really large engine with a bunch of reduction, too. I have a 2 QM 15 swinging a 13X12 2 blade. Full ahead, it'll push the boat 7-1/2 knots under ideal conditions. I don't have a tach, but like to keep the boat speed at 5 1/4 knots (keeps me honest as far as putting the sails up to you know... SAIL .
Anyway, it's the diameter of the prop. that'll give you the 'punch' you are looking for. Because the aperture of the Alberg limits us to about 13" wheel diameter, I really doubt you will be able to efficiently use all the power you have available. I have been told props are at max theoretical efficiency when their numbers are 'square', i.e. 12X12. 13X13, etc.
The tug I have been on until recently has wheels 78X64 and it outperforms most everything in it's HP range, so I'm inclined to think there is as much art as science in wheel selection.
Michael Grosh #220 Checkmate Tug Endeavor