advice please on 15 hp versus 9.9 hp outboards

[CSY Man]

. That said, pushing a three ton 29 footer is far more a function of the prop design and drag issues than it is the raw horsepower.

If ya are going to haul around an 80 lbs lump on the transom, might as well get full power out of it by going for 15 instead of 9.9. One day it may come in handy.

[tenchiki]

The P.O. put a Yamaha 8ph long shaft high-thrust in a well on my 24ft 2T sailboat on SF Bay. It is annoying to be dragging that big prop, but it will do hull speed against any wind I've tried it in... 99.9% of the time it has been serious overkill.

[Cheechako]

Originally Posted by alansmith

Thanks guys. Yup, good luck trying to lift 105 lbs out of a motor well when I weigh 170 lbs and Mid 60's

No one really addressed the main question though. Would you pay the money for 50% more power if u r already spending that much money for a new one?

One guy asked about the hull configuration. Double ended with upswept stern. They were used as oyster boats before 1900's and then to deliver mail from offshore packet ships over breaking sand bars.. surf boats.. I draw less than 2 foot with centerboard up. Pointy at both ends with excellent speed off of the wind. Not great upwind since she is a schooner with unstayed masts. I don't even have a single winch on board. Just pulleys, jam cleats, and rope.

The answer to that is money. We cant answer that. Who wouldn't want more HP in the same size and weight if it wasn't for money?

[ebsail]

That extra 5 HP comes at the top end of the rev range where most of us never go. I'm currently driving 25' 4800 lbs. (probably weighs well over 5000 + loaded) with a extra long shaft 6 HP Tohatsu and am well satisfied. It drives us at about 5.5 K (hull speed) and has the larger high torque prop and gearbox. A 9.9 and 15 will develop the same power at the same RPM. The 15 will rev to a higher number where it will develp the additional 5 HP

[zboss]

I just checked about converting a newer model Yamaha 9.9 four stroke to 15 and it is not possible. The cubic inches of the block are different.

Anyhow, Suzuki makes a 20 HP that weighs only 4 more pounds than the Yamaha 9.9

[billdre]

I have a 28' O'Day that weights 7400 lbs. When I replaced the outboard a few years ago I went with a 9.9 Mercury Big Foot. Which is a competitor to Yamaha's High Output model in that is has a larger, low gear trans-axle and a 4 bladed oversize, equally balanced (forward and reverse) prop. At the time I considered going to 15hp but it would have meant more weight and increased torque to the mount. I wasn't sure the transom was strong enough and had no way to evaluate it. So I went with the 9.9. It's on an extra long shaft, 25", plus a hydraulic assisted mount. After 5 years the only time it struggled was going straight into 20+ wiinds in 8ft seas from Newport RI to Point Judith in Rhode Island Sound. It still drove the boat at 4knts but it was a struggle. Also mounting waves at a 45 degree angle the prop never came out of the water. That sail was an exception. Normally I don't go out in that kind of weather but it left me confident in what the 9.9 could handle on my boat. But I credit the specific gearing and large prop for doing the job. The best thing about it normally is that it pushes or pulls with equal strength so that makes the boat very maneuverable in addition to the ability to lock the rudder and steer with the outboard itself.

[astokel]

My 9.9 4 stroke pushes my 26 footer at hull speed (6 knots) at quarter throttle and uses almost no fuel. I motored across lLake Ontario for $12.

If you increase the throttle, the bow points up and water starts coming in the drain holes.

[hsi88]

I will never put another outboard on the back of a sailboat without remote shift and throttle. There are also 9.9 models with power tilt. Of course there is also electric start and kits for remote steering. These things remove the biggest pains in operating an outboard on a sailboat. Unless you like leaning your body over the back of the boat, I would make sure what I bought had at least some of these options (in particular remote shift and throttle).

[a64pilot]

Originally Posted by zboss

Anyhow, Suzuki makes a 20 HP that weighs only 4 more pounds than the Yamaha 9.9

I have that motor, outstanding motor, pushes my 3.10 RIB past 30 kts and as I said appears to be immune to ethanol.
But it is not high thrust, and this application is a high thrust one, I'd expect a high thrust 9.9 would work better than a speed 20 HP, all the time burning less fuel and maybe making less noise, should accelerate and stop better.

Pure trivia but 10 HP outboards disappeared way back in I think the 60's when laws were passed outlawing 10 HP and larger motors from a great many fresh water lakes etc. So of course that brought about 9.9 motors, sort of like the heavy half Ton pickups, the Chevy 1500, Ford 150 etc. In the 70's I think it was the larger than half ton PU's were considered Commercial vehicles and didn't have to pass some mandated restrictions passenger cars did, so the Ford F100 and Chevy 1000 ceased to exist, cause they were not considered Commercial vehicles.

[smj]

Originally Posted by zboss

I just checked about converting a newer model Yamaha 9.9 four stroke to 15 and it is not possible. The cubic inches of the block are different.

Anyhow, Suzuki makes a 20 HP that weighs only 4 more pounds than the Yamaha 9.9

The older Yamaha 9.9 high thrusts were down tuned 15's, same cubic inches. The new Yamaha 9.9 high thrusts are up tuned 8's, same cubic inches.
Honda makes a xl shaft high thrust 15 hp in the US that has worked well for us.

[NakedCity]

Since you have such a confined space I would be looking for a nice used 2 stroke that fits your engine well instead of remodeling the boat .I am old school and much prefer the superior power/weight ratio or 2 vs 4 strokes.
For same reason go for a 15 instead of 9.9

[silversailor]

One thing to consider in choosing a motor is how gears are changed. In the Mercs that I have owned, the gear shift was integrated into the handle so it wasn't necessary to to reach to the side of the motor to change gears. Very handy. Don't know if they are still made that way.

[nautitrix]

Go ahead and use the 9.9 as it is a detuned 15 horse-power in almost every case. It will last longer. Save fuel and be happy Many inland lakes are restricted by law to motors under 10 horse-power. Many insurance companies also change a higher premium with the larger engine. The manufacturers just restrict the carburetor by either jetting or intake size. If you get a sailboat outboard you will get a special gearbox and a sailboat propellor but the key element is the sailboat propellor as it will give you more thrust with no cavitation, and work much better in reverse as well. Your average 9.9 is designed to run an aluminum runabout at flat out speeds. If you try to push real mass with it you will find a lot of cavitation sucking the fuel down little whirlpools and spitting it out as bubbles off the prop. (figuratively speaking) I have rescue towed a 38 foot heavy displacement boat with an appropriately propped 9.9 for several miles.
Your boat will go forward eventually with any prop but stopping is best with a sailboat propellor.
Fair winds

[flyingfin]

Are you planning on buying a 4 stroke or 2 stroke motor?? Will it be permanently mounted, or must you remove when not on the vessel?
Do you plan on motoring in any rough water? Need this info before we can make recommendations

[Cheechako]

Re-thinking experiences: my heavy-ish 30 ft long keel had 25 hp diesel. It was fine. My 31 ft beamy had 17 hp diesel.... a little bit small..