19X17 .5 Propeller - Albin 28 with Yanmar - Maybe this is the reason...

[Bluewater]

When I bought the boat (2000) at the end of last year I neglected to note the propeller dimensions. Hauled out yesterday and found I have a 19 x 17. 5. Having cruised sailboats (under sail whenever possible) all my previous life, my knowledge of suitable props dims is dismal. But I have been concerned at the fact that my Yanmar 6LP-STE, with 1300 hours, seems to be pushing the boat at much slower speeds than most others ((13-14 knots at 3300 rpm and 16 knots at 3800 rpm).
Am I correct in assuming that the prop should be 18 or 19 and with less of a cup?

[Norseman]

Either the wrong prop or you are loaded with stores, gear, tools, spares, etc, OR the hull is water logged..

I got a 2001 with a 19X18 prop that is nearly perfect, if anything it is slightly underpropped. (At light to medium load I get 17 knots at 3,600 RPM)
If you get between 3950 and 4050 RPM at WOT, the prop size/pitch should be ok, but you may be loaded or have a dirty hull?

I am also an old sailboater, but had no pride, motored instead of tacking, sold my spinnaker on eBay: Light winds was tackled by the Perkins 4-108.

[Bluewater]

No reason to believe the hull is waterlogged - but I guess I could buy a moisture meter. I usually travel with lightish load - other than I tend to keep the tanks full.
You’ve confirmed, I think, that I’m under propped. What cup is your 19x18?
And, BTW, thanks for the response.
And the 4-108 was my favorite - tractor engine, naturally aspirated, and run for ever at 1800 rpm.......

[tdsull]

David, I recently had the injectors rebuilt, wow what a difference. Almost zero smoke or soot on the hull since. I was cruising the other day at 18 knots into a stiff headwind and 2 foot seas, rough stuff for the bay . Others will know better than me but I think it’s pretty common for Albins to be routinely under propped out of the factory.

[Norseman]

. What cup is your 19x18?

Not sure what my cup is, will pull out the prop specs in a bit and post it right here.

[Bluewater]

Tim - Thank you. I see re-building the injectors in my future. 18 knots into a 2 foot chop is excellent - what is your prop?
Norseman - thanks in advance.

I’m going to cheat a little and ask another question - my trim tabs don’t have zincs. I cant remember if my 1994 had them or not, and looking at other 28s I see some with zincs and some without. Is there a clear wisdom on this?

[Carl]

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Bennet zincs

[Norseman]

This prop was fitted to my boat 6 years ago: I get 4050 RPM at WOT, perhaps a tiny bit “underpropped”

[Bluewater]

Thanks guys. I’m definitely under propped........

[Norseman]

Thanks guys. I’m definitely under propped........

I got another prop tweaked to a slightly coarser pitch, say 50 less RPM at WOT, but not tried it yet: Planning to swap next haul-out but bottom paint is holding up good after 26 months, will probably do it next year. The current prop is good, no vibration etc, but only seeing 17 knots at max cruise RPM 3,600. Should be slightly more perhaps, 18 would be good in my book. ( I see some guys reporting 20-21 knots but over-propping can be deadly with the Yanmar’s, they have a low tolerance for abuse as per the experts)