Pulls to port under power
- Thread starter pbknowles
- Start date
Can we assume that when under sail your boat tracks well without and drift? When holding a course, do you find your self constantly adjust the course? If so, perhaps just perhaps you have slop in the cables that run to the rudder quadrant. This would allow the rudder to move ever so slightly but enough to feel resistance..
My H27 that had been reengined with a 2gm20f and the PO had used the prop that came with the used engine during the refit. It was a 14" 3-bladed bronze prop. While spinning, the prop came very close to the bottom of the hull. The pull to starboard at above 5kts under power was terrible. I replaced it with a 13" 3-bladed with slightly more pitch and the pull to starboard disappeared.
PB, my guess would be that the diameter of your prop is too big. Also three-bladed props do this more than do two-bladers. The matter of prop walk is exacerbated by more blades and/or more diameter (pitch doesn't seem to have as much effect). The prop blades' attempting to 'roll' or 'walk' sideways (to the right, at the stern) is given more 'bite'.
You might try reducing the diameter and increasing the pitch. That will lower the RPM (reducing torque) and reduce the blades' leverage (arm and moment) and tendency to prop-walk.
Also, you might tighten the steering cables. If there's any slack in there, the prop walk may read that as free rein (literally, like with a horse) and take up the slack (also literally).
I would NOT tighten the steering-wheel brake, as that will only lead to more frustration for you and wear on the system. That's never more than a temporary fix in any situation.
If you have an autopilot with a SEPARATE cable set, you might try setting the autopilot to see if the problem is the same. If it is, I'd say it's the prop. If it's better, inspect the tension of the main-steering cables.
Correcting the wheel by one or 1-1/2 spokes (not the space; I mean the diameter of the spoke itself) to starboard is pretty normal. Much more than that indicates a serious problem.
Independent spade rudders (no skeg) should include about 18% of their area forward of the rudder post (given a vertical or near-vertical rudder shaft). It is the same for the area of a fixed skeg. As my dad designed that boat (and taught me that design parameter), I don't think a rudder with ZERO area forward of the post sounds original. If you're inclined, you might consider adding and shaping a hunk of foam to the blade and then 'glassing and fairing it over. It will help overall performance. Substantially more than 18% = it will hunt, side to side, and horribly. Substantially less than 18%, it may stall when turned more than a few degrees. No area at all forward of the rudder post would not produce the effect you describe; in fact the opposite effect would be the case - the rudder, left alone, would just follow along doing nothing actively. The fact that the boat actively steers itself to the left only when under power strongly suggests a problem with prop-diameter/RPM mismatch.
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You might measure, with a 4-digit micrometer, the exact diameter of the rudder shaft and reach out to Tides Marine. They can make a perfect-fit UHMW bearing for really any size. The bearing will be hammer-fit only - ZERO tolerance, thus having ZERO leaks, but you've got to be sure to measure it precisely. Not the cheapest place in the world but truly a market leader. OEM-standard on the very best boats.
(Tell 'em I sent you
)DoB, thanks for your reply post. I was away from the boat and working from memory....you are correct there is a balance portion ahead of the shaft. Also I found buried in the papers that came with the boat a receipt for "install used propeller provided by owner". Probably over propped, plus I have the 40 hp Yanmar....
I have not been able to find what the original and correct propeller would be.
I have not been able to find what the original and correct propeller would be.