Hard to handle under power

[Isla30]

When motoring, I need to hold the tiller hard with both hands as the ruder wants to continually shift from one side to another. My boat is an Islander 30 and it has a balanced rudder. It also has a two blade folding prop wich I don't like and I intend to replace with a fixed blade prop during the winter. Will a different prop change anything? Other than that I have no idea where to start to ease this problem.

Thanks

Daniel

[COOL]

I had the same issue on my Islander 30 II.
Most of my time under power was spent with
the tiller braced against my leg, the boat wanted
to do a full brody if you eased off on the tiller.
I do not think a different prop will have an effect,
it will still send a blast of prop wash straight into
the rudder. A fixed prop will only make the boat
sail slower.
I eliminated this problem on my boat by removing
the inboard Atomic 4 and installing an outboard on
the transom. The boat performs much nicer under
power or sail now.

[SEMIJim]

Originally Posted by Isla30

When motoring, I need to hold the tiller hard with both hands as the ruder wants to continually shift from one side to another.

That's fairly common. We have it with our Pearson P30.

Hint: There is an amount of throttle beyond which you'll find you gain little speed but the engine is working much harder and so are you. For us, in relatively flat seas and with little-to-no headwind, that is right around 6 kts. With no headwind and very flat seas she'll do 6.5 knts comfortably. Abracadabra's hull speed is 6.7 kts, IIRC.

Originally Posted by Isla30

It also has a two blade folding prop wich I don't like and I intend to replace with a fixed blade prop during the winter. Will a different prop change anything?

First of all, Daniel, your boat is a "she," not an "it."

As far as having to keep a firm grip on the rudder: No, a fixed prop won't do much, if anything, for you. You'll get a bit more forward speed and better reverse, at the cost of losing speed under sail. In light air: Quite a bit of speed lost. When our folding prop became ill, and we temporarily swapped it out for the fixed two-blade prop we had, we noticed a significant loss under sail.

Originally Posted by COOL

I had the same issue on my Islander 30 II.
...
I eliminated this problem on my boat by removing
the inboard Atomic 4 and installing an outboard on
the transom. The boat performs much nicer under
power or sail now.

I find it exceedingly difficult to believe that any 30' boat performs "well" under power with an outboard motor hanging off the transom.

Coincidentally: Just brought to the top by a comment: Pearson 31 inboard or outboard

Jim

[Isla30]

Jim, you have a point, if I ease off the throttle it's not so bad, it's just that I usually want to get to our sailing ground ASAP, so I tend to go wide open throttle. Installing an outboard motor means that I would need to remove the swimming latter, which is not an option. Plus this would de-value the boat when its time to sell it.

Thanks

Daniel

[Faster]

Anytime a balanced (or overbalanced..) rudder is subjected to the direct prop wash this issue will be present. It's caused by the force of the prop wash on the balancing tab/area of the rudder ahead of the post.

Reducing to minimum thrust for the speed will help, as has already been pointed out. You can probably find a balance between reduced speed vs reduced forces so that the extra couple of minutes it will take is probably worth the easier steering effort.

Agree too, that the outboard is a drastic "cure" though a cure it is.