9.9 or 15 HP Outboard on 25' Boat?

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ChiTownSail

ChiTownSail

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Dec 8, 2011
68
Hunter 25 Chicago
I am looking and replacing my outboard Johnson (15 hp) and am debating between a 15 horse power 20 inch shaft or a 9.8 horse power 25 inch shaft.

Its for a Hunter 25

On are current 15 hp when lake mich gets choppy the prop comes out of the water and races.

Not sure if trading the hp for prop depth is worth it.
 
T

tommays

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Oct 2, 2006
1,517
Jboat J24 commack
25" shaft with a real high thrust prop is big to begin with on a 25' boat and plenty of power

Just have to be sure you can get the 25" out of the water when it is not in use
 
JoeWhite

JoeWhite

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Mar 6, 2008
1,293
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
On my Hunter 25.5. I installed 4 cycle 9.9 HP with 25" shaft. If it is shorter it will come out of the water 9.9 HP is plenty of power.
 
Tom

Tom

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Sep 25, 2008
73
Lancer 28 T Great Lakes
I use a 7.5 HP long shaft Honda on our 28 foot Lancer and we're on the Great lakes.
never had a problem.

tom
s/v GAIA
 
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C

captcoho

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Oct 29, 2012
353
Catalina 30 TRBS MkII Milwaukee
Had a Johnson 9.9 Sailmaster on my Catalina 25 with a three blade high thrust prop.
It would push the boat to hull speed and still wanted to go, to the point it got a little shakey beyond the hull speed.... Electric start,generator, and controls in the cock-pit.
It was more than enough even when it was rough. But barely got it out of the water, even when raised up, when sailing on a starboard tack.
And as far as a 4-stroke, they weigh almost twice as much as the two-stroke. And the fuel on the port side balanced the boat, unless it was less than a quarter full.
Johnson/Evinrude 9.9 hp and 15 hp are the same block/engine.....
Mercury 7.5 hp and the 9.9 are the same, at least in the older models.
 
Doc_holiday

Doc_holiday

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Nov 19, 2011
1,489
MacGregor 26S Hampton, VA
I have a 9.9 merc and it does great, I am not sure how long my shaft is, but if I go to the bow to raise the jib, the motor comes out of the water in waves. 9.9 will push my Mac 26 6 knots at about 2/3 power.
 
Charlie Jones s/v Tehani

Charlie Jones s/v Tehani

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Mar 1, 2012
2,182
1961 Rhodes Meridian 25 Texas coast
??an 8 hp 4 stroke pushed my (loaded0 7500 pound 25 footer at hull speed at UNDER the start setting.

Problem is NOT hp- it's keeping the prop in the water. Truth be known, 6 HP is probably plenty for OOMPH.
 
jibes138

jibes138

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Jan 27, 2008
3,086
ODay 35 Beaufort, NC
Weight on the end of the boat is bad as it contributes to pitching. So you want the least weight that will give you the power you need. I had an 8 HP on a Catalina 25 after I replaced a 9.9 that was originally on it. The 8 was more than enough power.
 
RECESS

RECESS

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Dec 20, 2003
1,505
Pearson 323 . St. Mary's Georgia
I had a 9.9 on my O'Day 25 and took it offshore all the time. It was plenty of power even in rough seas. The 25" shaft kept it from windmilling when cresting a swell.
 
C

Crazy Dave Condon

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Jun 8, 2004
10,375
-na -NA Anywhere USA
Generally most of the 15 hp engines use the same block as their 9.9, 9.8 or 10 hp whichever. It is the carbureation that is different which gives you the extra horsepower. However, most 15 hp engines will not make the boat go faster as the top hull speed is achieved by the 9.9 whether two or four stroke. However, it is the construction of the transom that you have to be worried about to include the motor brakect if four stroke. Most transoms were built for a 10 hp max engine. The transoms on a power boat is a different animal due to the engine generally found on the back.

I have traditionally never sold an engine over 10 hp ofr sailboats as I saw no need for a 15. If you are heck bent on so doing, then do not go to full throttle. If the bow of the boat under power starts to raise up, then you will slow down and must back the throttle down to avoid plowing in the water.

crazy dave condon
 
B

bffatcat

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Jun 8, 2004
853
Pearson 26W Marblehead
outboards

MY 2c
Ive got a fairly new Tohatsu 8Hp 4 cycle 20" long shaft for my Pearson 26 w It replaced an old Mercury 8 HP 2 cycle The Tohatsu pushes the boat at hull speed about 1/3 throttle If I motor into a chop I may need 1/2 throttle. This motor has far more power than the old Merc.
If I had it to do over again I would drop down to a 6HP The 20 in shaft has never come out of the water The boat displaces 5200 lbs Please be careful about overkill, Namely buying a motor thats to big for the boat.
 
RECESS

RECESS

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Dec 20, 2003
1,505
Pearson 323 . St. Mary's Georgia
Another consideration in determining the size, is do you need to motor against any strong tides or currents. Sometimes it is necessary to go a little bigger.
 
ChiTownSail

ChiTownSail

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Dec 8, 2011
68
Hunter 25 Chicago
Well we pulled the trigger for the Tohatsu 15hp 20". We had an old Johnson 15 HP 20" and it seemed to work ok, so we went with the 15hp after much debate. One nice thing is the charging system is bigger on the 15hp. Thank you all for the good information.
Now, due to the weight difference we need a new mount. Who do you recommend? I have been looking at the Garelick ones and have come across a few that are on deal, but they are the 9.5" drop down. The boat is 65 miles away for the winter and as soon as I get back up there I am going to do some measuring. In the meantime, any thoughts on the mount?

Thanks!
 
Charlie Jones s/v Tehani

Charlie Jones s/v Tehani

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Mar 1, 2012
2,182
1961 Rhodes Meridian 25 Texas coast
RECESS said:
Another consideration in determining the size, is do you need to motor against any strong tides or currents. Sometimes it is necessary to go a little bigger.
Click to expand
Sorry but if the engine you have will push the boat to hull speed (non planing, displacement hull), more horsepower won't make you go faster, current or no. You're gonna make hull speed against the current, but won't make anything more over the bottom.

example- hull speed 6 knots, 5 knot current- you're gonna go 1 knot. No matter WHAT horsepower you're running.
 
Sumner

Sumner

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Jan 31, 2009
5,254
Macgregor & Endeavour 26S and 37 Utah's Canyon Country
TSBB 2 said:
Sorry but if the engine you have will push the boat to hull speed (non planing, displacement hull), more horsepower won't make you go faster, current or no. You're gonna make hull speed against the current, but won't make anything more over the bottom.

example- hull speed 6 knots, 5 knot current- you're gonna go 1 knot. No matter WHAT horsepower you're running.
Click to expand
We used a 5 HP Nissian once and had no problem running 5+ knots into a 25 mph wind but in Florida a couple times in cuts with a 3-5 knot current running I don't think the 5 HP would of had the thrust to move us even 1 knot against the current. The larger prop, with the lower pitch on our 9.8 HP did the job. Would the 5 HP worked as well in the same situation? I don't know but we'll keep the 9.8 HP ;).

I'll go along with almost ever other posted on this thread and say that the 9 HP would of been a good and mayber better all around choice in the OP's case than the 15,

Sum

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Our Endeavour 37

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jibes138

jibes138

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Jan 27, 2008
3,086
ODay 35 Beaufort, NC
The force of current on a boat is far greater than the force of wind on the hull (no sails up). I forget the factor but it is something greater than 4X more force. So in other words a 5 knot current will push the boat more than a 20 knot wind. Somehow I think it was more like a 7X factor but I don't really remember. Anyone else store this factoid anywhere?

How much current is there in Lake Michigan?
 
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