A25 inner shaft bearing

[honza]

Is there supposed to be a bearing in front of the shaft log? Some people mentioned it. A prop/shaft guy tells me, that the shaft is too long to be unsupported. Does it have to be there? What kind? Another cutless? Nothing is shown in the handbook. Has anybody tried to use 1.25 in. shaft in the A25? (All the stock 16 x 12 props seem to be for 1.25 in. shaft.) Thank you.
Hull #1110

[dkirsop]

Early A25 models came with a 21HP motor and a 25mm shaft. Later models had a larger motor installed and the shaft increased to 30mm. None of them had an intermediate bearing. I have an early model and find it works well. The cutless bearing is self-aligning which helps in aligning the engine to the shaft but you still have to follow the correct procedures to make sure the shaft flange is correctly mated to the tail flange of the engine. Given that these boats are approaching a life span of 50 years you should not worry about shaft size and bearings - they have proven to be very dependable.

[DesertAlbin736]

Given that these boats are approaching a life span of 50 years you should not worry about shaft size and bearings - they have proven to be very dependable.

Dave, our 1971 boats, and Honza's as well, will be 50 years old next year. Shall we try for 100?

1.25" = 31.75 mm, a 6.75 mm, or 0.266 inch difference compared to a 25 mm shaft. The key issue would be the cutlass bearing. Wouldn't somehow adapting a 1.25 prop to a 25mm or 1" shaft be better idea? When owners previous to our PO re-powered with the Yanmar they had to switch from left hand prop to a right hand prop. I'm pretty sure the shaft is still a 25 mm, so they figured some way to find a prop with a matching shaft size or an adapter to make it fit.

[WillieC]

The WillieC has a 30mm shaft, 36 HP engine. When we got it the shaft was so out of line with shot engine mounts, a real mess. In my new boat owner zeal I finagled another cutless bearing from the Jenneau/Beneteau line that is simply a rubber bearing with no brass/bronze outer casing. I made it fit the upper end of the shaft log and then proceeded to align the engine, now that the shaft was nicely centered in the log.

All that...I agree with Mr. Kirsop, likely not much help once you get everything aligned. As low power, low speed as these as the original A25s are, even though it is a bit of a long span, the added bearing is not really necessary. (However, I think the Swedish Albinmotor site shows an inner or upper bearing for sale. That would have to be coordinated with the original gland shaft seal. Anybody still have that setup?) Turns out my shaft whacked bottom at some point and put a nice kink at the prop end of the shaft that my prop guy corrected as best he could. No wonder it was making such a racket.

I may have some pics on my MD17C thread. Have the prop shaft checked for runout, make sure your prop is straight. Have them face your coupling and make sure your mounts are good and the engine properly aligned. 16X12 sounds like the earlier AD21 engine. Mine is 17X14 by the book, 17X13 installed.

If not the original engine, there may engine mount "issues". Some engines want a more flexible mount, to reduce vibrations, that may make solid couplings not ideal. DA has the super duper liquid flexi magic aqua velva drive that plays nicely with his Yanmar. That is a nice set up, but not cheap.

[honza]

Thank you guys. How about the prop, is it acceptable to use the prop/ shaft reducer, or shall I keep trying to find or special order the prop with 1 in. bore? Looking at Michigan DJ 355, for instance. I am getting the Beta 25 and need to go from LH to RH.

[ssrig]

If you are purchasing a new prop have it made for the prop shaft size, reducers work but from what I hear they are not recommended.
I had a new prop made to the right size last year, the previous owner had a reducer that was made from nylon and it wore away which loosened the prop nut and away it went! He did have a diver get the prop and reducer but never found the nut.
Most prop suppliers have sizing formulas to get the right diameter and pitch for your power plant and you supply the shaft dimensions etc.

[ssrig]

https://www.vicprop.com/displacement_size.php
This is one of them and the one I purchased my prop from.

[Dieselram94]

Mine has a 1.25” shaft. It’s tight but fits nicely. I just replaced the old bronze 1.25” shaft with a new stainless shaft last summer. In my opinion it does not need a upper bearing for support, at least with a 1.25” shaft...

Top picture shows how out of alignment and close the old shaft was to inside the stern tube.

Last pic is of my cutless set up. It’s a 1.25” cutless (bind) pressed lightly inside of bronze collar that may be original? It looks as if it was machined to accept the new size cutless. A excellent set up...

[WillieC]

You can get whatever bore you want from a good prop shop. With my original prop and 84" shaft in hand, my supplier ordered from Michigan wheel and specified the taper. He meticulously measured everything in inches and pounds while I nervously chewed my fingernails hoping he carried the one and converted the perpendicular to the apex...Then I showed him how I got there in meters and kilograms...30mm shaft tapered to 22.5mm in 75mm length. 7.5mm taper in 75 mm length. 1:10....gotta love metric. It took some six weeks for Michigan Wheel to check our maths and deliver my shiny new prop but it fit like a glub. So glad I collaborated with and went through my prop guy so I didn't end up with a tastefully stunning, ostentatiously overpriced coffee table conversation piece.

DA has an adapter betwixt his prop and shaft. Works fine. I chose to match the new prop to the shaft. All this while trying to decide whether to stay with the Volvo Penta, left hand drive, MD series engine. All is connected and all is up for grabs when swapping engines. I wanted to stay with the 30mm shaft as Albinmotor still supplies the funky Albin cutless bearing since I couldn't figure out how to make a real brass Dynomax cutless bearing with an OD larger than my shaft log fit. Albinmotor also supplies a few sizes in SAE. Glad to see dieselram figured out how to make off the shelf parts work. The self-centering feature of the original, and its attendant mounting method, seem critical to the whole operation and not something I have seen anywhere else. Now a little fiberglass work, with a machine shop in your back pocket, could fix the whole thing and make it "modern".

[DesertAlbin736]

Our AquaDrive thrust bearing CV joint.

Aqua Drive_markup2.jpg

[WillieC]

"...need to go from LH to RH."

Just flip it over...

[Desertboater]

The Michigan DJ 355 propeller seems to be a 10 inch diameter propeller - at least the Michigan prop that is Product Code: 3B10DJ355 comes up as a 10 inch propeller.

We replaced the AD21 with a Beta 25 (2.6 to 1 reduction transmission) and a new 1 inch prop shaft along with a replacement cutlass bearing from Albin Motors in Sweden sized for a 1 inch shaft rather than 25mm. The Michigan Wheel propeller was purchased for a 1 inch shaft

However the 3 blade Delta Jet style Michigan propeller selected was 14 inch diameter.

The "Prop-It-Now" calculator on the Michigan Wheel web page was suggesting a larger size (16 to17 inch).

https://www.miwheel.com/inboard-propellers/prop-it-now/

However, the problem with a larger prop is insufficient clearance between the prop and the hull or the rudder skeg. The Michigan Wheel FAQ has the following about clearances:

The clearance between the propeller blade tips and the hull bottom should be at least 15% of the propeller diameter and ideally, 20% or more. So for example, a 20” diameter propeller would have 3” minimum clearance and better still 4” or more. A common guideline for recommended propeller to strut or keel clearance is 20% of propeller diameter measured between the propeller blade edge and strut leg or keel. This is often measured at a point on the propeller blade edge about 70% of the distance from the shaft centerline to the blade tip.

[dkirsop]

The standard prop for the AD21 was 16.5" D x 12" P. I cut mine down to 16" dia. and had the blades cupped which actually gave me a slightly better performance. I have a 2:1 reduction gear so my prop rpm when cruising runs between 800 and 900 rpm and reaches max. rpm of 1050 at WOT. I typically plan my cruising using an average SOG of 6 knots running the engine between 1600 to 1800 rpm. The clearance does not present any problem.

[Dieselram94]

The Michigan DJ 355 propeller seems to be a 10 inch diameter propeller - at least the Michigan prop that is Product Code: 3B10DJ355 comes up as a 10 inch propeller.

We replaced the AD21 with a Beta 25 (2.6 to 1 reduction transmission) and a new 1 inch prop shaft along with a replacement cutlass bearing from Albin Motors in Sweden sized for a 1 inch shaft rather than 25mm. The Michigan Wheel propeller was purchased for a 1 inch shaft

However the 3 blade Delta Jet style Michigan propeller selected was 14 inch diameter.

The "Prop-It-Now" calculator on the Michigan Wheel web page was suggesting a larger size (16 to17 inch).

https://www.miwheel.com/inboard-propellers/prop-it-now/

However, the problem with a larger prop is insufficient clearance between the prop and the hull or the rudder skeg. The Michigan Wheel FAQ has the following about clearances:

The clearance between the propeller blade tips and the hull bottom should be at least 15% of the propeller diameter and ideally, 20% or more. So for example, a 20” diameter propeller would have 3” minimum clearance and better still 4” or more. A common guideline for recommended propeller to strut or keel clearance is 20% of propeller diameter measured between the propeller blade edge and strut leg or keel. This is often measured at a point on the propeller blade edge about 70% of the distance from the shaft centerline to the blade tip.

If you had to repower again, would you stay with 25hp?

[honza]

I have similar setup of the cutlass as Dieselram has. It is a standard, of the shelf 1x1.25x4 bearing. A couple of pictures is at the bottom.

It is not so easy, in my end of the woods, with the prop shops. The closest being at least hundred miles away. I think it makes a lot of sense to use one for repairs, bent shaft, or so, but I do not see much advantage using one for buying a new prop and shaft and paying several hundred $ more, not mentioning the travel. Should one decide, that slight turning of the face of the shaft flange is needed (amateur checking for perpendicularity should be easy) , any local machinist, who has got 7 ft. space behind his lathe, should be able to do it.

So, if it is going to be coming on UPS anyway, the question is: Has anybody made a good (or bad) experience with one, or more of the web based prop/shaft shops? Thanks.

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