Outboard/Kicker-prop depth in water?

[Sailon1]

I am installing a 5 hp outboard auxiliary kicker on the stern. How far underwater should the prop be?
General advice (for power boats) is to set the cavitation plate about 2 inches below water.
Sailboats, however, behave differently than power boats and particularly in following seas the transom could lift high enough to raise the prop out of the water.
Your real- life experience and suggestions are appreciated!

[tkeithlu]

I recommend that you get the prop into the clear flow of water under the boat, not a particular depth in the water. The peculiar shape of the stern of the Pearson 30 (it looks like the bow shape) may be a consideration. Whether you will lift the prop out of the water on a following sea is dependent on a bunch of factors, including weight distribution in the boat, speed, and the size of the following sea you are likely to get into when operating the motor.

[thomm225]

On a sailboat, you need the outboard to go as deep as possible. It's not like a power boat at all because the stern will rise on a sailboat with a small outboard and the prop will come out of the water.

A 5 HP 4 stroke outboard has been my main engine since 2011. I have a 25" extra long shaft and can get the prop about as lower at the prop was when the boat had a diesel with the adjustable bracket the motor is mounted on.

In second video, I'm crossing the 20 miles or so of lower Chesapeake Bay on a calm morning. (on autopilot)

https://www.youtube.com/watch?v=Jz9x5oRthfk

https://www.youtube.com/watch?v=cpZhq35etcw

[thomm225]

Motor can be up a little higher in smooth water.......that is until a boat comes by with a big wake.

Adjustable bracket on second notch down here. On third notch in video in posts above.

https://www.youtube.com/watch?v=uNl2tPRC-Tw

[Lake-Effect]

We have a 5 hp outboard on a 19 ft sailboat. In a really lumpy sea or a wakefest, the prop occasionally comes out of the water. So the answer is: have your bracket set up to be able to put the outboard prop as deep as possible. thomm225 has provided great info.

[lydude]

I’m trying to get a 26 foot sailboat in the water. Having trouble getting my diesel to start ordering parts etc. pretty sure I’ll eventually get it going. Don’t really want to give it to the pros just yet as I figure the money I’ll save would pay for an auxiliary motor. Was thinking about putting an auxiliary motor on a bracket with a 5 hp 25 “ shaft. Is that enough HPfor mainly getting in and out of the harbor or do I need to go with something bigger like a 9.9 in case the diesel is totally kaput. Appreciate any input. Thx.

[Lake-Effect]

Originally Posted by lydude

I’m trying to get a 26 foot sailboat in the water. Having trouble getting my diesel to start ordering parts etc. pretty sure I’ll eventually get it going. Don’t really want to give it to the pros just yet as I figure the money I’ll save would pay for an auxiliary motor. Was thinking about putting an auxiliary motor on a bracket with a 5 hp 25 “ shaft. Is that enough HPfor mainly getting in and out of the harbor or do I need to go with something bigger like a 9.9 in case the diesel is totally kaput. Appreciate any input. Thx.

Diesels need air, fuel and compression. If the Diesel was starting and running fine before (eg last season) then the fix should be simple.

Anyway, on a 26 ft boat, a 5 hp outboard will get you in and out of a marina, if the wind, waves and current aren't too fierce. As a permanent solution, a 9.9 outboard would be the minimum I'd consider, and a 15 would be better if you want to motor in all conditions.

Check with other owners of your model of 26ft sailboat, and find out what they're using.

[thomm225]

Originally Posted by lydude

I’m trying to get a 26 foot sailboat in the water. Having trouble getting my diesel to start ordering parts etc. pretty sure I’ll eventually get it going. Don’t really want to give it to the pros just yet as I figure the money I’ll save would pay for an auxiliary motor. Was thinking about putting an auxiliary motor on a bracket with a 5 hp 25 “ shaft. Is that enough HPfor mainly getting in and out of the harbor or do I need to go with something bigger like a 9.9 in case the diesel is totally kaput. Appreciate any input. Thx.

See videos above.

My boat is a 27' full keel sailboat, and it has a displacement of 6600 lbs.

I'd be willing to bet it's at least 1,000 lbs heavier than your 26' boat.

I have used a 5 HP 4 stroke 25' shaft outboard for the last 10 years in lots of different conditions from leaving the marina in strong winds to crossing the lower Chesapeake Bay where it meets the Atlantic in some pretty good size waves.

The 5hp weighs around 57 lbs and is easy to start and you don't need a battery or control cables.

That is another reason why I chose that size engine plus the fact that my first 5 sailboats didn't have engines and I competed in at least six 100 mile races.

The 9.9's are good engines but weigh at least 100 lbs and are $1,000 more expensive.

I can reach down and remove my outboard and place it on the stern railing mount unassisted.

[thomm225]

James Baldwin has a 6hp outboard in the well on his 8,000 lb displacement 28' Pearson Triton

And the best thing of all about having an outboard is that they are new! Not some ancient leaky 30-40 year old diesel.

https://www.youtube.com/watch?v=PuFLhAJI1zA

[Jammer]

Originally Posted by thomm225

On a sailboat, you need the outboard to go as deep as possible.

Thomm speaks my mind although there are tradeoffs. I have an extra-long shaft (25") Yamaha high thrust 8hp that is presently on a fixed mount that keeps it deep enough for me to be able to motor sail when the motor is on the weather side of the boat.

The tradeoffs. Ideally you would like to be able to get the entire outboard out of the water when moored. Indeed ideally you would like to get the entire outboard out of the water when sailing even when the motor is on the lee side of the boat (assuming it is not on the centerline).

And you want the powerhead to be high enough up that it will not be damaged through inundation by a following sea.


Various kinds of movable mounts help with this, but pose their own tradeoffs.

[Jammer]

Originally Posted by Lake-Effect

Anyway, on a 26 ft boat, a 5 hp outboard will get you in and out of a marina, if the wind, waves and current aren't too fierce. As a permanent solution, a 9.9 outboard would be the minimum I'd consider, and a 15 would be better if you want to motor in all conditions.

I have a 26' boat that is beamy and hard to push (Hunter 26). 8 hp is more than enough in heavy wind, waves, and current, and will drive the boat beyond hull speed.


But you must have a proper high-thrust motor that is designed for low speeds. These have a lower final drive ratio, that is one that results in the prop operating at a lower speed compared to crankshaft speed. They also have room for a larger diameter prop, and they come stock with an extraordinarily flat-pitched prop.


My outboard is a Yamaha 8hp high thrust. The stock prop was 11.75" three blade, 5.75" pitch. I have just replaced it with an aftermarket four-blade 5" pitch prop which I expect will perform better as the 5.75" prop never allowed the engine to reach target RPM.


On a sailboat, a high thrust motor will outperform a standard outboard with a standard prop that has 2x the horsepower.


Depending on maker there are high thrust outboards available starting at around 5hp and going up to around 15 hp.

[thomm225]

Originally Posted by Jammer

Thomm speaks my mind although there are tradeoffs. I have an extra-long shaft (25") Yamaha high thrust 8hp that is presently on a fixed mount that keeps it deep enough for me to be able to motor sail when the motor is on the weather side of the boat.

The tradeoffs. Ideally you would like to be able to get the entire outboard out of the water when moored. Indeed ideally you would like to get the entire outboard out of the water when sailing even when the motor is on the lee side of the boat (assuming it is not on the centerline).

And you want the powerhead to be high enough up that it will not be damaged through inundation by a following sea.


Various kinds of movable mounts help with this, but pose their own tradeoffs.

Right.

I see lots of outboards at my marina that are not totally out of the water.

But luckily I can get mine totally out, and the plan is when I start cruising long distance to pull the outboard and put it on the stern railing when offshore.

Winds were gusting over 30 knots in video below (as you can hear in the rigging) and seas reached a steep 7' but the outboard was fine on the run across the lower Bay last September.

It was wind against tide also. I made the 20 mile crossing in 3 hours but broke the dodger frame and the bow lights no longer worked due to being submerged a lot.

Waves were breaking over the side until I was able to turn DDW.

I had too much sail up and couldn't get it down so the boat was pushing lots of water....

Video is near the end of the crossing when I was in sync with the conditions even with the camera at my eyes

https://www.youtube.com/watch?v=-nXfjcCuiPk

[campbdon]

I don't think anyone answered the original question, namely how deep should the prop (or more properly, antiventilation plate) be submerged. I would assume that Jammer was looking for a range in inches from minimum to maximum depth acounting for wave action and avoiding swamping the power head. I'm interested in knowing too.
Thanks
DonC

[thomm225]

Depends on the boat, how big the waves are, and a few other things, but basically as deep as you can get it.

On my boat, I can get the outboard even with the bottom stern of the boat or a little deeper.

If the waves are large enough to swamp the power head, you probably won't be using the outboard anyway so the bracket will be all the way up which on my boat puts it above the deck a bit

My bracket has 4 slots. It looks to be on the second or third slot in the photo so it can be put deeper in the water if need be

See pictures

Bracket is on the third slot down in the video. I motorsailing around some anchored tankers then going back to sailing

https://www.youtube.com/watch?v=ri0c5GnZ1I8

[Jammer]

Originally Posted by campbdon

I don't think anyone answered the original question, namely how deep should the prop (or more properly, antiventilation plate) be submerged. I would assume that Jammer was looking for a range in inches from minimum to maximum depth acounting for wave action and avoiding swamping the power head. I'm interested in knowing too.
Thanks
DonC

The standard advice is that the anticavitation plate should be one inch below the waterline or level with the bottom of the transom, whichever is lower. A little lower is OK.