What Size Outboard

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Re: What Size Outboard

Postby Brent65 on Mon Dec 06, 2021 6:17 pm

Hey all,

I spoke with Pete McCrary today, builder of Tattoo. His favorite outboard for his PS was the Tohatsu Sailpro 6hp with 25" shaft. This motor weighs 61 lbs, comes with a high trust prop which is 8.375" diameter with a low 6" pitch. This is ideal for moving heavy items at a slow pace over an extended period. Pete loved the motor for the convenient F/N/R gearbox and the long 25" shaft which allowed him to cut away the transom for easier access while still keeping the prop in the water. Though I cringe at cutting away the transom, it does make a very convenient, safe way to handle the motor. And, I've never liked hanging the motor further aft with the use of a vibrating, spring loaded bracket. Since I plan to motor a lot, this is probably the route I'm leaning toward. No it doesn't move the boat any faster than a smaller motor, but it does move the boat at hull speed at lower rpm which might make it quieter. If you're motoring the boat for multiple days, this could be an advantage. Just some thoughts...
Brent Butikofer
Build Blog: http://www.idahopocketship.wordpress.com
Previous Builds: Scamp, Skiff America 20
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Re: What Size Outboard

Postby afairaizl on Mon Dec 06, 2021 9:25 pm

The post discussing the transom cutout for Tattoo is here with a diagram and measurements. viewtopic.php?f=3&t=531&start=10
Thanks,

Drew - Hampton, NH, USA
PocketShip 'Dreams Won't Wait'
Build Started: Oct 2021
Boat Launched: May 5th, 2023
Build Blog - https://www.dreamswontwait.com
Photo dump = https://photos.app.goo.gl/dS2tViRpgq4YZH8o6
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Re: What Size Outboard

Postby Tom G on Thu Dec 09, 2021 2:12 am

Definitely not a 15. It will won't stay in the water in big waves. I had one from another boat and tried it and it would even come out of water if you were up forward messing with the sails, like furling them as you motored along. I have a 20 inch at it works fine with adjustable mount. You might get a 15 to work if the mount went low enough but then it would be really difficult to reach and operate. I don't put it down all the way in calm conditions as it is easier to operate if the power head is up higher. If the waves are big in rough conditions I move it down a notch to make sure it stays in water sufficiently for cooling. (not a problem if you have Honda air cooled!)
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Re: What Size Outboard

Postby afairaizl on Thu Dec 09, 2021 7:52 am

Tom, thanks for the explanation on the wavy days. It looks like I'll be aiming for standard long shaft at 20 then.
Thanks,

Drew - Hampton, NH, USA
PocketShip 'Dreams Won't Wait'
Build Started: Oct 2021
Boat Launched: May 5th, 2023
Build Blog - https://www.dreamswontwait.com
Photo dump = https://photos.app.goo.gl/dS2tViRpgq4YZH8o6
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Re: What Size Outboard

Postby craig on Thu Dec 09, 2021 10:12 am

I've never tried a larger motor on my Pocketship, so I can't speak to personal experience. And sure, larger motor = slower RPM for hull speed = less noise. Agreed all around. And obviously your boat, your call! haha. I guess in my opinion, I can't see the noise reduction being so large as to balance the MUCH heavier weight hanging off the transom (double in this case, from 30 to 60 pounds) and the resulting negative effect on weight distribution and sailing properties. Plus the possibility of a large cutout in the transom, which is a pretty dramatic change.

All to say, everyone has different priorities. I'm sure you already have done so, but my advice would be to think hard about whether more money, weight, and big alterations to the boat justify the lower noise. If you can get a noise reading on a small motor vs. larger motor at the RPM you will be running at, that's even better. I guess I've never heard a quiet outboard - they are all noisy.

Totally agree on the long shaft vs. short (15in). Mine is 15in and I wish I had the longer version (which wasn't available at the time I bought mine). Short shaft does work, although in big rollers your prop will partly come out of the water at the crest (still good for emergencies or short periods of time, though) . On lakes, quiet water, etc it is fine all the time.
Titania, launched January 2015
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Re: What Size Outboard

Postby Brent65 on Thu Dec 09, 2021 2:48 pm

craig wrote:I've never tried a larger motor on my Pocketship, so I can't speak to personal experience. And sure, larger motor = slower RPM for hull speed = less noise. Agreed all around. And obviously your boat, your call! haha. I guess in my opinion, I can't see the noise reduction being so large as to balance the MUCH heavier weight hanging off the transom (double in this case, from 30 to 60 pounds) and the resulting negative effect on weight distribution and sailing properties. Plus the possibility of a large cutout in the transom, which is a pretty dramatic change.

All to say, everyone has different priorities. I'm sure you already have done so, but my advice would be to think hard about whether more money, weight, and big alterations to the boat justify the lower noise. If you can get a noise reading on a small motor vs. larger motor at the RPM you will be running at, that's even better. I guess I've never heard a quiet outboard - they are all noisy.

Totally agree on the long shaft vs. short (15in). Mine is 15in and I wish I had the longer version (which wasn't available at the time I bought mine). Short shaft does work, although in big rollers your prop will partly come out of the water at the crest (still good for emergencies or short periods of time, though) . On lakes, quiet water, etc it is fine all the time.


Craig, I appreciate your comments. Yes, we all have different applications for our sailboats, which seems to drive our outcomes. My desire to use the Sailpro 6 is based more on the following issues than the sound. Sound may be a benefit but as you've noted, probably insignificant. I see the following as the benefits of the 6 hp Sailpro.

1-The availability of a 25" shaft. This will allow me to mount the motor with the skeg (the lowest part of the outboard) 1" above the bottom of the rudder while still being able to operate the controls. The extra length makes this possible. In this fashion, the rudder should hit ground before the outboard. Yet the outboard will be as deep as possible for a solid grab in the water. Remember, the lower you go, the denser the water. The negative will be that unless you take the time to shim the transom, the 25" long shaft may drag in the water when sailing. But, properly shimmed, I'm told the Sailpro does not drag in the water when heeled.
2-High thrust prop. The wide 8.375" diameter prop combined with the 6" pitch is designed to push heavy items at a slow rate. This is ideal for all day motoring up a narrow channel when exploring. You might be able to add this prop to a smaller engine, but it appears to be optimized with the 6 hp engine.
3-Lower RPM's. Based on actual users, the 6 hp allows you to reach hull speed at 1/3 throttle, with plenty in reserve for unexpected situations. This should prolong the life of the motor, be quieter and create less vibration, though the actual amounts might be insignificant.
4-A Reverse Gear. I've never quite gotten comfortable swinging the outboard 180 to reverse. I seem to throttle the wrong directions when timing matters most. If you can go the 6 hp engine, you get a reverse on the front of the motor for easy and quick gear changes with intuitive steering.

If weight were the same, I would for sure want these benefits.

OK, but the weight isn't the same, so what about that extra 30 pounds? If you're willing to cut away the transom (and I know that's a big request), you get to subtract the outboard bracket weight because you will be mounting the outboard directly to the transom. Some claim the outboard brackets can weigh 20 lbs, I've never weighed one. I do know from personal experience, they are prone to vibrate (which creates more noise), and they're cumbersome and clunky. Hence, my decision to direct mount my outboard.

Also, if you're willing to cut away the transom, the motor mounts further forward, reducing the lever arm effect of said motor weight. Also, by cutting away the transom, you can sit further forward in your boat when operating the outboard. If you weigh 200 lbs like me, this is not insignificant. Also, the gas now resides in a small 2 or 3 gallon tank in the footwell (No, you don't have to fill it full). The visual tank eliminates range anxiety, but also moves yet more weight forward in the boat. And, finally, you can subtract the weight of the transom you removed. When you add all this up, I'm not convinced there exists much of an overall weight differential between a 2.5 hp 30 lbs outboard (mounted with a standard outboard bracket hanging off the back) and the 6 hp 60 lbs outboard (directly mounted to the transom).

At the end of the day, each sailor needs to choose whatever he is most comfortable with and go with that system. I'm confident both approaches probably work acceptably well in most situations.
Last edited by Brent65 on Fri Dec 10, 2021 4:53 pm, edited 3 times in total.
Brent Butikofer
Build Blog: http://www.idahopocketship.wordpress.com
Previous Builds: Scamp, Skiff America 20
Never Stop Exploring
Never Stop Learning
Brent65
 
Posts: 48
Joined: Tue Jan 14, 2014 1:55 pm

Re: What Size Outboard

Postby craig on Thu Dec 09, 2021 8:51 pm

When you put it that way, Brent, I see your points. Especially considering the weight gained/lost by removing the transom cutout and outboard bracket. Absolutely best of luck getting it set up and I hope you will report back on this forum about your experience when you are done! In any event, hopefully the discussion helped you be more sure about your decision :)
Titania, launched January 2015
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Re: What Size Outboard

Postby Brent65 on Thu Dec 09, 2021 10:20 pm

A hearty thanks to all for a most excellent thought provoking discussion regarding outboard motors. It was very helpful for me as I narrowed down my options.

Best,
Brent
Brent Butikofer
Build Blog: http://www.idahopocketship.wordpress.com
Previous Builds: Scamp, Skiff America 20
Never Stop Exploring
Never Stop Learning
Brent65
 
Posts: 48
Joined: Tue Jan 14, 2014 1:55 pm

Re: What Size Outboard

Postby Wayne G on Sat Dec 11, 2021 11:20 am

I have great respect for Pete McCrary and have used a lot of his suggested modifications, and went for the 25” shaft sail pro based on his posts to this forum, however, I would never consider cutting out a section of the transom. As the outboard is mounted towards the edge of the transom and not the center where the rudder is located the prop needs to clear the sloped boat bottom at that location which is considerably less then below the rudder. I use a fixed motor mount which allowed plenty of depth for the 25”shaft and is adequate for the 20”Honda, some photos attached.

On a side note, I have just returned from a week’s camping and sailing vacation. There was a strong tidal current which made returning to the boat ramp a real struggle with the 2.3hp Honda; I was making just over one knot at full throttle!

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Wayne Gray
Orlando Florida
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Re: What Size Outboard

Postby [email protected] on Sat Dec 11, 2021 9:28 pm

On a slightly different topic: where do you get that sail cover in the first photo? It appears to have a zipper instead of twist-locks for closing it up.
I am planning to sew my own sail cover soon, and I am trying to finalize the design. I am pretty sure I can make one like PS#1 has (in Weathermax) for under $200 in materials...

Wayne G wrote:I have great respect for Pete McCrary and have used a lot of his suggested modifications, and went for the 25” shaft sail pro based on his posts to this forum, however, I would never consider cutting out a section of the transom. As the outboard is mounted towards the edge of the transom and not the center where the rudder is located the prop needs to clear the sloped boat bottom at that location which is considerably less then below the rudder. I use a fixed motor mount which allowed plenty of depth for the 25”shaft and is adequate for the 20”Honda, some photos attached.
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