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Discussion Starter · #1 ·
Has any one added a hydrofoil to help their sailboat plane at slower speeds to prevent the motor from being drowned?

SE SPORTS? STINGRAY?
 

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not sure what you mean by plane, a CAT 27 is never going to plane. now with my 8HP outboard on my dingy it will plane. even with hydro foils on a 27 it would take about 1000 HP to make it plane
 

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Pretty much a non starter, methinks.....
 

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Discussion Starter · #4 ·
When i am at full speed the bow of my boat comes up a bit and the water line is very close to drowning my motor that is mounted in the transom motor well on my cat 27. I want to find out if by adding a foil if it will prevent my motor from digging deeper in the water and keep it level more?
 

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If anything I would look at the angle the motor is sitting at and play with the tilt pin setting

Some boats just stern squat as they reach displacement speed I know my Cal 29 starts squatting at about 5 knots

Its silly take the Cal above 5.5 as at 6.5 knots it squats so BAD the scuppers let in so much water your standing angle deep and the fuel burn about doubles :)
 

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Discussion Starter · #8 ·
My transom well gets lots of water in it and the motor is close to the main motor. How low can a yamaha 8hp 4 stroke go to water level before drowning out?
 

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Firstly it's not clear that you understand the concepts of displacement hulls, and hull speed.

Most sailboats have what are called displacement hulls, which are optimised for a mode where the water passes around the boat, instead of the boat riding over it like the planing hull of a speedboat. This means that your sailboat does not have the hull features which would make it plane - at ANY power (those features are large flat sections aft)

So you are stuck in displacement mode. A displacement hull has a concept called hull speed. This is the point where you are putting in more and more power, and not going faster. The power goes into the bow wave which gets bigger and bigger. As the bow wave gets bigger, the bow rises up it and the stern drops. This is your problem.

The fix is to go more slowly. I cruise at the point where the exhaust pipe is just above the water - about 6 kts on my boat.

I would expect your C27 to have a hull speed of about 6 kts, though you might get too much squat lower - as low as 5 kts.

You will also get much better fuel consumption cruising at the speed where the squat is small, as the power is going into moving the boat, not creating a huge bow wave.
 

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The trim of the outboard is one place to look, as mentioned above.. If by 'foil' you mean those fins they add to outboard cavitation plates, that might be worth investigating, but I'd be skeptical.

You may be powering on too hard (and likely not gaining any speed anyhow) so throttle back to reduce the 'squat' and see if things go better then. But also check the trim pin on the clamp bracket.. if the motor is tilted up aft, that will promote the 'squat' that's giving you problems. Try going to the lowest pin setting there.
 

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Discussion Starter · #12 ·
I believe i was already on the lowest pin on the trim bracket. Yes i was talking about the fin looking things.

If they work on other boats I cant see why it would not help even a little bit. A cheap expense for even an inch of additional room.

I cant seem to find anyone that has one on a sailboat though. I surely cant be the only one with this issue with my cat 27?
 

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not the only one with the issue. outboard powered sailboats have limitations on the conditions that it is safe to operate in. so far has the engine you have been a problem or is it that you are just worried about a problem that does not exist. if you find that going at top speed is drowning your motor then don't go that fast. problem solved.
 

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Discussion Starter · #14 ·
Im concerned about what could happen. My motor is running fine. I have never owned a outboard sailboat before. Need to figure out its limits.

Even a slight wave like .5-1ft is concerning.
 

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I'd experiment with the throttle and the knotmeter... back off until the 'squat' eases up some, and see if you really lose any significant speed. Displacement hulls pushed to that squat position often don't gain any real speed... they just burn more fuel and make bigger waves.
 

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Let's be sure what the problem is. Where is the water level on the outboard when the boat is at rest? Is it where it should be?

What shaft length is this o/b? Normally sailboats use the longest available, extra long, so that there is room for some wave action, squat, etc. It also makes the controls easier to reach.
 

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The Catalina 27 engine mount for the outboard is on the lowish side, always has been ...

 
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