Rudder vibration (sailboat under power)

[IrishSkipper]

I tested an 8-year-old Dufour 30 Classic yesterday and noticed significant vibration in the tiller/rudder when under power. The boat has a saildrive just forward of a large fin rudder (not transom-mounted).

The vibration was not noticeable under sail (albeit in an extremely light wind). The yachtbroker said this vibration was normal with sailboats.

Is it?

[camaraderie]

It is in a lot of boats with blade rudders and props close to them. I'd take a hard look at the condition of the saildrive...thay are a major pain from everyone I've talked to.

[Artwerke]

If you have a 2 blade prop close to a spade rudder a little prop wash vibration wouldn't be unusual. Art

[cardiacpaul]

may also be a cutlass bearing... how to tell?
if you have none in reverse, if it happens when you first go into forward, you have vibration, it may be...

[paulk]

If the rudder is working in the outwash of the prop it could be somewhat normal. It could also be a problem with a folding blade not opening all the way. There are lots of possibilities, and as mentioned above, ways of eliminating them until the correct reason is found. Where was your surveyor during this test sail?

[hellosailor]

In theory, for an ideal design, there would be no vibration. In practice, there are limits to where you can stick the prop and some boats are known to have a problem like that. You'd have to find other Dufour owners to ask about that. If you can't confirm/refute that, then as others have said you have to check the shaft, bearing, prop, to see if everything else is OK.

Sometimes it is as simple as someone putting on too big a prop--because they wanted more power under sail. And you might want to keep it, or change it out. No way to tell what prop is down there without getting eyes on it.

Also consider that if you don't want to pay for a haul (or diver) before the sale, you can ask for an escrow provision in the contract, where a certain number of dollars are put aside in an escrow account against the possibility of certain specific repairs, i.e. seller to pay up to $1000 for drivetrain repairs if worn or damaged prop, prop shaft, strut, or cutless bearing is found by a professional within 30 days after the sale. That gives you the chance to haul the boat for inspection and repaint after you own it, and if the seller is SURE there's no problem...neither of you is at risk.

[yotphix]

With all due respect to hellosailor's advice, pay for a haulout before you buy a boat. This time and every time.

[hellosailor]

Yotphix, I don't disagree with you about a haulout, but in an imperfect world......that's what escrows are for.

[IrishSkipper]

Excellent advice from everyone, thank you. I'll consider my options ;-)