Outboard motor on C-23

[jcatkeson]

My 23 came with a 8 hp o/b. grossly overpowered. That aside is there some way of determining the correct pitch and diameter for a propellor? There may be a problem with this as I discovered that with a gps reported speed of 4.8 I was using a gallon of fuel for each five miles  with the throttle setting at "shift" Any more than that the boat starts to squat.
I have no experience with outboards and no idea what is reasonable with a two stroke.

[HideAway]

I disagree on the grossly over powered part -- I have a 1994 two stroke 8hp Evinrude for HideAway.  It burns about a gallon an hour - yep that's a lot.  Recently I was crossing a 2-3 knot current heading into a marina at Johns Pass towing my dink and loaded for a week long cruise - my forward speed was 3.7 - I was very glad to have eight horses as I was going sideways at almost the same speed.  A strange feeling.  I've had problems with the lower end of my old friend Mr E for some time now.  I was given an older 6hp evinrude yacht twin.  It ran well but as I was to discover the big prop was shot.  At the same time I had the chance to buy a new tohatsu for less than $800.  I know you guys like them a lot but my old Evinrude is a better motor over all.  So I combined the two putting the 8hp on the yacht twin lower end and had the prop rebuilt.    While the bigger prop does not have a noticeable effect on gas milage it more than makes up for it  with all that torque.  I can spin HideAway 360 at idle -wow.   A boat can only go to hull speed before it digs itself a hole and wastes serious gas.  Other factors are current and wind-- I know - I know but the ICW here is narrow and winds around. Very little of it is sailable.  If you are motor sailing throttle down and shift to neutral - Then decide if the difference in speed is worth the gas.  The only thing I would do differently is have a longer shaft - a friend of mine has a motor with a 28 or 30 inch shaft - He says it never cavitates.   If you do buy a new motor get electric start and alternator.

[CaptRon28]

The maximum prop diameter is set by how much space the engine manufacturer left around the output shaft. It's probably around 8 to 9 inches in your case. The correct pitch is based on what rpm you can get to at wide open throttle in forward gear. You should be able to do at least 90 percent of redline. Assuming redline is 5800 rpm, then 5200 to 5800 is OK. I tend to stay closer to about 90 percent. One other note, sailboats tend to do a drop better with a high thrust prop. That usually means 3 blades with around a 7" pitch (the prop screws itself into the water 7 inches for each revolution). A pitch of 10 or more will not work that well on a slower moving heavier boat. Much better suited to a light boat that is capable of going faster. You won't easily get a sailboat with a displacement hull to go faster than hull speed.

Note that 8 hp sounds reasonable for a 23.

[NateD]

My 2005 Nissan 9.9hp 4-stroke gets about 18mpg at 5-5.5 mph in dead calm conditions. 9.9 is a bit overkill, but if you're looking for significantly better fuel efficiency, you might need to get a 4-stroke.

[HideAway]

I think NateD is right - My main reason to get a 4 stroke is the fuel economy- an alternator would be nice too.    Hopefully I'll get a few more years out of the new Mr E    M

[mike gartland]

The CP 23 motor debate resurfaces every year or two.  When I lived on the Gulf Coast and had to fight tidal currents entering or leaving Galveston Bay I was happy to have the old 9.8 hp Tohatsu 2-stroke that came with my 23/3, especially when bucking currents and headwinds at the same time or the heavy chop when they opposed each other.  The old Tohatsu was finally starting to become a bit unreliable just about the time I retired and moved back home to Colorado a couple of years ago.  So I left the old smoker in Texas and bought a new 8 hp Tohatsu 4-stroke when we were settled in and were ready to launch WindRush in her new home (originally Lake Dillon and for the past two summers Lake Chatfield).  Can't tell you how much I like the quiet, the absence of blue clouds engulfing the stern at start-up, and the much better fuel efficiency of a 4-stroke...it seems like I go a whole month before I have to refill my 3 gal tank.  I would have preferred to replace the old 9.8 with a 6 horse but the Admiral insisted that the new motor have electric start...she has never had the snap in her arms to successfully pull-start an outboard...even the little Honda 2 horse on on Precision 15.  And I enjoy the alternator keeping the battery topped off for our frequent sunset cruises that bring us home after dark.  So the 8 horse was a compromise even though I no longer felt I needed that kind of power on a Colorado lake.  My biggest concern was the added weight of an electric-start, long-shaft 4-stroke which exceeds 100 lbs.  The transom of WindRush already showed spider cracks around the motor mount from the old 2-stroke when I bought her...not sure if a previous owner had attempted trailering her with the motor in place or not.  But before I saddled up the new 4-stroke I repaired all the transom cracks and installed a large backup plate on the inside out of 1/4 inch aluminum bedded in 3M 5200.  The result has been as hoped for.  I'm now entering my third summer with this modification and have no signs of stressing the transom with the heavier 4-stroke.  Now if I could find a way to improve the fore and aft balance of WindRush with adding weight to the bow I would really be a happy camper.
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Mike

[Bob23]

   I have a 1988 Nissan 8 hp 2 stroke on my 23 and it's more than enough power. I  prefer to have reserve hp because I sail in tidal conditions and occasionally have to motor into an oncoming tide and wind. The extra power does become a safety issue at times so it's nice to have.
  I always enjoy the 2 stroke vs 4 stroke discussions. I guess when Miss Nissan, size 8 decides to give up the ghost, I'll buy a 4 stroke. But she literally starts first pull, every time even when she's been napping all winter. Of course, I treat her right with a proper winterization program. Sure, she's a bit noisy and I guess she uses more gas than a 4 stroke, but I motor so little that it's a negligable issue.
   My Nissan is a long shaft but if I were to buy new, I'd get the extra long (25") shaft.
Bob23