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Motor Size?

May 26, 2020
2
Sirius 21 Montague Harbour
What's the appropriate size for an outboard for the Sirius 21?

Before I describe the size we have, I'll describe the use case... we're in tidal waters with the occasional need to be in passes with currents. We don't go through at peak current, but 2 knots might be a good outside limit.

I'm mainly worried about overpowering, and falling over with the rig up.

What power motor would be too much for this boat?
 
Nov 6, 2006
9,185
Hunter 34 Mandeville Louisiana
A 4 HP or a 6 HP would be really fine.. much bigger and the weight will be too much..
 
May 24, 2004
6,750
CC 30 South Florida
2 stroke or 4 stroke? The average 2 stroke will weigh half of a similarly powered 4 stroke. With tidal currents of 2+ knots I would like to see an 8HP . Small 2 stroke engines are no longer sold in the US but those that were in use have been grandfathered in and some good ones can still be found in the used market. The boat displaces 2,000 lbs. so it should be able to handle a 4 stroke 70 lbs. engine. Check and see the weight specs on the 4,5 and 6HP engines as some manufacturers will use the same displacement engines with different carburetors to widen the RPM range and accommodate different propellers with no discernible increase in thrust. If you want to know how your motor mount will handle an specific weight just hang something that weights the same as the engine. It is not fun moving at 1 knot over the bottom when you are fighting a strong current head on.
 
Sep 22, 2018
1,869
Hunter 216 Kingston
What's the appropriate size for an outboard for the Sirius 21?

Before I describe the size we have, I'll describe the use case... we're in tidal waters with the occasional need to be in passes with currents. We don't go through at peak current, but 2 knots might be a good outside limit.

I'm mainly worried about overpowering, and falling over with the rig up.

What power motor would be too much for this boat?
First of all welcome to SBO!

I don’t have specific knowledge of your model of sailboat so went Googling :)
and found this.


It would appear the designers were specifying less than 10hp and at the time of writing I assume that was a relatively heavy 2 stroke. Lots of new choices now and maybe just a prop change will help.

You express your concern in your original posting but I’m not quite sure what that is??? Can you elaborate?

Is this a new to you boat or are you just considering repowering?
 
Sep 16, 2015
8
Sirius 22 Tampa
I use a 6HP on my Sirius 22, pretty good current in and out of the canals to Tampa Bay, never had an issue.
 
Oct 22, 2014
15,740
CAL 35 Cruiser moored EVERETT WA
All of these comments are smack on. :plus:

But then there is a school of thought out there that asks...
Is There Such Thing As TOO Much Outboard Motor Horsepower On A Boat?
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Granted an outboard is an auxiliary power source for a Sirius 21. Here is a video of a 21 owner with a 9.9 on the back...

You want to have a mount that will get the motor out of the water to improve your sailing.
 
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Sep 22, 2017
27
Sirius 21 Clear Lake
We have a Johnson 9.9 two stroke. Probably over kill, but the boat was my fathers and he had been caught a couple of times in Gulf of Mexico squalls, and decided when the 6 hp died he wanted more. Now that I have her, it is just a lake sailor and probably a little overpowered but works.
 
Oct 31, 2012
434
Hunter 2008 H25 Lake Wabamun
You probably already know this but ensure you get a long shaft and mount it at the correct height above the waterline. I’ve seen boats with outboards mounted too high where the prop pops out in wavy conditions and motors mounted too low that drag the leg when sailing.