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Excessive stern "tuck" under power

7K views 39 replies 20 participants last post by  Jeff_H 
It's an Autoprop - what is the pitch? Your Tazwell 43 / 55 hp combo is good with the 22 diameter.

The soot says you are over-propped (unburned fuel), but you say you reach full RPM which makes no sense.

Either way, I think you need to lower the pitch and reduce the load on the engine to prevent the soot. You should be able to reach full hull speed (about 8 knts) at 2/3 RPM, any more is a waste and not efficient.

A waterline length of 35.33 (i.e. yours) isn't that much different from mine - 32.5, and I run a 16 x 15 auto prop on 44hp just fine to hull speed.
 
Chuck,

Autoprops are supposed to be self-pitching. The blades are supposed to rotate into the ideal pitch and automatically adjust as the conditions change. I know there are a lot of people who love them, but I also have spoken to people who have talked about issues with Autoprops in a range of conditions where they felt that the prop did not self adjust properly, one being the over reving the engine for the boat speed. But their main gripe seemed to be in choppy conditions where the prop seemed to be changing pitch and altering the behavior of the engine so that the engine would seem to cycle from bog to race and back.

The other comment is that although the Taswell has a similar waterline length that is not all that much longer than your boat, it is a wildly heavier boat with a D/L around 324, vs your boat with a D/L is somewhere in the mid-240 range.

Off the topic and FWIW, I have never understood why the Taswell 43's are so absurdly heavy. Its predicessor, the Norseman 443 has two feet more waterline, has roughly the same tankage and a lot more ballast, and weights 4-5,000 lbs less. I have never understood why so few Norseman 443's were built or why Ta Shing replaced them since the 443's were a nicer boat all around.

Also off topic, I have been thinking about your chainplate redesign. I have a few ideas, but I keep coming back to the idea of reinforcing the hull in that area, adding athwartships knees tied at the top and bottom by a longitudinal stringer, and bolting straight chainplates to that knee.

Jeff
I was thinking of my MaxiProp - It's adjustable. Not enough coffee in the morning.
Yeah, it's a bunch heavier (32k vs my 21k - as weighed this fall when I hauled it out).

As to my chain plates - and not to take the thread too far off track - I'm limited to the skill of the repair guy and his budget. That's me.
I'd need a NA to re-engineer anything else as that would considerably change the position and angle of the plates.
Not in my budget or time schedule.
 
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