SO37 Turns Right Under Power

[brandleside]

I have owned my 2006 SO37 for two seasons.

The boat has a tendency to turn to the right under power. This was apparent with both the OE fixed 3-blade prop in the first season and with the Kiwi Prop fitted last year.

I have always just assumed that this was a characteristic of the vessel's fundamental design and prop rotation as there is no such turning tendency under sail.

However, after sailing with a friend this weekend, he felt that this was not normal.

The tendency is not particularly pronounced below about 4kts, but becomes increasingly apparent at higher speeds. By 6kts some pressure is required to keep the boat on a straight course otherwise she veers off to the right.

I have also noticed that the autohelm sometimes wanders and wonder if this has something to do with the same issue.

The engine is Yanmar 3JH4E (40hp).

Has anyone experienced similar characteristics, or could there be something wrong here?

[Zanshin]

My old 43DS had the same effect and the 49DS does as well, but to a much lesser extent. I think this is normal, just prpor/walk or precession. Or similar to prop wash in an airplane with a single prop.

[iseath]

I have the same effect on my SO 362, but dont see it as a problem. Its because of the drag of the water thrown outward by the prop. This rotating paddlewheel effect is less pronounced above the propellor (because of the hull) than below, the result being a small force one way or the other. It should be easily overcome by adjusting the wheel tension adjuster. The same effect causes the boat to slew one way or the other when starting to go astern - an effect which can of course be very useful in tight corners. Sounds like the sensitivity/gain of your autopilot needs adjusting as well.