Depth of propellor

[gunship]

when a sailboat heels so much the prop is too close to the surface, you'd most likely be sailing, no?

and if you're rolling so much when motoring that ventilation would be an unbearable problem, I'd guess sea conditions are such that ventilation wouldn't be among the top concerns...

[michael pierzga]

Sailboat frequenly motor dead to windward to navigate narrow channels or harbor approachs under power. You need a good bite with the prop. The classic example of a bad prop bite is a small day sailor with an outboard motor hung off its transon. When the bow dips into a wave, the stern rises and the motor cavitates in bad water..

[gonzo]

No, it does not cavitate. It ventilates. They are completely different things.

Originally Posted by gonzo

No, it does not cavitate. It ventilates. They are completely different things.

Not for Michael, Gonzo. He is a sailboat "Captain" with many hundreds of thousands of miles at sea, you know? He sails 1200 miles per week. Almost every week. And he does it with a cavitating prop, I guess.

[gonzo]

Michael: A sailboat heading straight upwind into a harbor entrance would be leeward of it. That means calm water and little wind.

[gunship]

Originally Posted by gonzo

Michael: A sailboat heading straight upwind into a harbor entrance would be leeward of it. That means calm water and little wind.

And only pitching, no rolling. there would need some giant waves to make a relatively long sailor pitch so hard that the props are out of the water... in that case the waves would probably stop the boat from moving, engine or not.

[BATAAN]

Originally Posted by Fitzroy

I was thinking of a bar crossing situation under power with a following sea

BERTIE's off-center prop is about 20" below LWL and will sometimes ventilate slightly when heeled on port tack and it's very rough. Don't think it'll be much a problem with a centerline installation though.

[BATAAN]

Originally Posted by michael pierzga

Sailboat frequenly motor dead to windward to navigate narrow channels or harbor approachs under power. You need a good bite with the prop. The classic example of a bad prop bite is a small day sailor with an outboard motor hung off its transon. When the bow dips into a wave, the stern rises and the motor cavitates in bad water..

I've seen several bad harbor entrances that had the wind blowing out of them so hard that they made a difficult sea in only a short fetch. BERTIE was tied to a pier when a human muffin in charge of a small day sailor with o/b on transom lost control under just this scenario and rammed us midships at full throttle, nearly sinking him. I understand the concern here but if the prop is where the original designer put it and the boat is loaded properly as was intended there should be no problem under normal conditions. As for abnormal conditions, every vessel has its limit all the way up to the finest CG surfboats, and when you pick the vessel you own, you must accept those limits or shop for another.