I used to have that same fixed 2 blade prop on my boat years ago. At the time
on flat water I'd get 5.9 @ 2800 RPM. I changed to a 2 blade geared Varifold 15
x 10 and I now get 6.1 @ 2800 on flat water.
Allan RheaumeDrumroll30-2 #90
On Sunday, November 10, 2024 at 08:39:56 p.m. EST, ejwills1993--- via
CnC-List <[email protected]> wrote:
Hey all -
I have a 30 Mk II with the original Yanmar 2GM20F and factory Martec 15D x 11P
x 1 2-blade brass prop. About 850 hrs on the engine, seems in great shape.
Issue: I can only motor at 2200 RPM before the engine/stern begins to vibrate.
This puts me at a max cruising speed of 5 kts.
>From the survey, one of the prop tips measures about 1/8 inch farther AFT
>(axially) when at 12 o’clock position versus when the other tip is rotated to
>the same 12 o’clock position. The prop blades are not chopped/scraped and the
>prop appears to be otherwise symmetrical in all other dimensions.
The engine does not vibrate when revved to 2800-3000 rpm in neutral.
The shaft does not wobble, and there is no leakage from the shaft packing.
Q: What cruising speed should I expect from this boat and the Little Yanmar? I
think the spec in the Yanmar manual says cruising rpm should be 2700-2800 rpm
without breaking a sweat. I’m not expecting to motor at 8-9 knots like a big
sailboat but I do expect to be closer to the 30-footer hull speed of around 6.7
kts.
I’m trying to figure out if this is a valid excuse to get a folding prop :)
Thanks!
-Eddie W.
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