Outboard for Pedro 17

[Drewd]

Here is a picture of my Pedro 17 boat. She’s just being repainted and once that’s done she needs an outboard. Obviously originally she was a day yacht but since has had the sails removed and an outboard was put on her. This was not included in the sale so now I’m on the hunt for an outboard. My problem is how big of an outboard can I put on her? I’m looking at a 40hp mariner long shaft 2 stroke but I don’t want to pay out for it if it’s going to be to heavy for the boat. The size of the transom is 20”. Any help or advice will be greatly welcomed.

 

[southkogs]

Welcome aboard:

I've not heard of anything much more than a 10HP on a sailing hull up to about 24'. I think the general rule of thumb is about 4HP per 2,000#. A sailboat transom would likely not have been built to handle the force of a 40HP pushing on it ... you'd need to make sure that a proper transom was constructed in that hull to really trust it.

Also realize, that boat is a displacement hull with a hull speed of probably around 6 knots or so. To get much past that hull speed you have to add enough power to make that displacement hull climb up and plane on top of the water ... a 40HP won't give you enough power. You'll need something closer to a solid rocket booster So, I would work with the expectation of 5knots and start with a 10HP if you can find one.

Sailboat outboards typically have a lifting bracket or they are a 25" shaft length.

 

[Scott Danforth]

i would use an electric trolling motor or a 2-4hp outboard. a 40hp is way to big for a 17' sail boat that weighs 2000#

http://sailboatdata.com/viewrecord.asp?class_id=6078

as 'kogs mentioned, if your trying to get a displacement hull to plane, you need about 400hp and then it wont be stable (as in you wont be able to control it). displacement hull speed is 5.5 knots. you can achieve this with a trolling motor or a 2hp motor

if you want faster than that, you need a longer boat, or a different hull design (planing hull vs displacement hull).

https://www.easycalculation.com/physics/classical-physics/hull-speed-calculator.php

 

[Maclin]

Yeah, need Ferrari level HP I'm thinkin

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

Just a Lighthearted take on it, but this boat was having problems and rocking back and forth pretty bad at the end

 

[Sea Rider]

We use Tohatsu 2 strokes 15-18 HP engines to power J-24 and larger 30 footer sailboats with maximized props while sitting on reinforced engine mounts with 0 issues so far.

Bear in mind that if the sailboat will be used with removed mast, sails going per much less 6-10 HP standard engines, add extra boaters, will achieve a boaring displacement speed and surely lug the engine badly if used as factory delivered.

With a larger OB with maximized prop can achieve fast displacement speed 10 knots or more, which is the speed that comes right after displacement speed. Just distribute deck weight evenly for sailboat to run parallel to water level and voila!!. Correct trim and engine height is a must have for sailboat to perform well. Reinforce transom if needed.

If a sailboat runs fast at fast displacement speed with adequate sails and wind, why won't it run same powered with a larger engine as stated.

Happy Boating

 

[Drewd]

Thank you for your advice.

I understand your comments about displacement and plaining hulls. I’m not really bothered about speed at all my big concern is bad weather as we live next to Loch Ness in the Highlands of Scotland where the winds can get pretty harsh real quick. I've seen small boats like mine get in to trouble due to having a small outboard. What I’m looking for is a big enough engine to push me through the bad weather to a mooring. As you say and I agree that my boat will be more than happy with a 2hp but if the wind gets up a 9.9hp will hold me still in the water but won’t get me to a mooring safely I don’t think?

What are your thoughts?

 

[QBhoy]

Hi
you definitely can’t put a 40hp on this boat. Likely a 6-10hp be more than enough. Apart from that. Displacement hulls have a displacement max hull speed. Achieved by a certain hp....anything more is a waste of time really. I have never seen an outboard any larger than a 9.9hp on any single hull sailing boat.

 

[southkogs]

... but if the wind gets up a 9.9hp will hold me still in the water but won’t get me to a mooring safely I don’t think?

Good question, and to be honest I don't know certainly. The equal risk is that the 40HP outboard pushing on a weak transom in rough weather would fail - and you'd be fighting taking on water too. By adding a larger outboard, you're in essence trading one risk for another.

Sea Rider's probably right about some outboards up in the 18HP range. If they'll work on a bracket, then I think that's your best bet for additional horsepower. But realize the hull you're using was probably not designed to fight storms - rigged properly or not.

 

[Sea Rider]

Interesting thread...

Some issues :

If plan installing a larger OB, will it be on a side mount or middle built transom ? If with a SS OB mount Garrelic type, adjust all bolts and nuts to have minimum side play and replace plastic/acrylic mount with same size hard wood one, if not , OB will vibrate excessively and mount will crack open and lose dear OB going into the deep blue if not secured with rope or drag it down the sea bed if secured with rope, both scenarios are bad musique LOL!!

Sailboats are not designed to be planing hulls, are darn heavy to plane, just achieves fast displacement speeds whether hull rides inclined sideways with hard wind or while powered with correct OB's sizes.





Which 2 strokes outboards are available where you live ? If Tohatsu are available used or new go for a 30 HP one, weights10 kilo more than any 10-18 HP OB, will need to maximize a prop though. If going that route can give some nice tech parameters for engine to work as a champ powering Pedro 17 back to land safely.



OB's are factory delivered with medium pitch props, once break in period has ended need to dial a prop in order for OB to rev middle to max wot rpm range as usually loaded, which very few boaters go for..



The issue nobody uses larger OB's than 10 HP ones is mostly by word of mouth, besides distorts the sport, you've bought a sailboat, not a power boat, right. Add added OB weight along losing portability if need to put and remove OB from mount/transom constantly, worse if being an avid elderly boater.

These examples are from three different 24-30 footer heavy sailboats powered with 15-18 larger OB's, fully used when there's 0 wind to power their respective sailboats, Speeds are around 5-6 knots when loaded and as much as 12 knots in flat water cond when lightly loaded, all 3 with maximized props to rev full wot rpm when lightly loaded.

Happy Boating

 

[H20Rat]

Hi
you definitely can’t put a 40hp on this boat. Likely a 6-10hp be more than enough. Apart from that. Displacement hulls have a displacement max hull speed. Achieved by a certain hp....anything more is a waste of time really. I have never seen an outboard any larger than a 9.9hp on any single hull sailing boat.

That isn't really how displacement hull speed works... Hull speed is just defined as the wavelength between the two created waves equaling the length of the boat. IE, you end up in a hole... I've had my non-planing 17' sailboat up to around 16 mph. Very clearly well above displacement hull speed. All that the displacement hull speed tells you is that you are going to need a bump in power to get past it, it is certainly not impossible though, depending on hull design.


In any case though, 40hp is too much weight on that. I'd keep it under 20 max, a 10 would be ideal.

 

[Sea Rider]

I'll have my doubts a 10 HP-OB will take OP safely back to Terra Firme if encountering harsh winds that's why OP was asking if a 40 would be OK. Powering a small OB as an aux, it's not same as powering a larger HP-OB as an aux or main power plant whether for pottering around or taking you back home safely.

Anyway, just expect displacement speeds with less HP-OB's and fast displacement speeds with larger HP ones. To plane a sailboast is Mission Impossible with any portable OB. Let's see what OP has in mind, wants to do as it's his decision not ours.

Happy Boating

 

[roscoe]

If you really want a trailerable motor/sailboat, you should get one like a MacGregor 19 Powersailer.

It will do 25 mph with a 40 hp outboard. And its built to handle the power.

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

The Macgregor 26 is a pretty awesome sailboat.

 

[GA_Boater]

I have concerns with hanging much weight off of the transom. It seems thin and the tiller opening doesn't help matters.

 

[Sea Rider]

A far away shot pic can't say much, if transom thickness is at least 3/4 of the swivel bracket's internal lenght, will be OK.

Happy Boating

 

[Old Ironmaker]

Interesting thread indeed. The question reminds me of a neighbour in Cottage country in the dead of winter asking what tires she could buy to get her low slung rear wheel drive sportscar with ground effects through 2 to 4 feet of snow so she doesn't get snowed in.

 

[Sea Rider]

If I would ever buy same kind of sailboat, would reinforce both middle transom sides with 1.0 mm SS plates. If most boaters likes going per max 10 HP-OB's, whether short or long shaft ones, should know that 15's are detuned ones from 9.9/10 HP ones, consequently weights exact same, in that case go for the larger OB and prop it right to push sailboat happily.

But if dealing with strong currents, harsh winds as described by OP, needs a 30 HP minimum...

Happy Boating