Hi I have an oday 23 favtory calls for a 15hp but I wanna sail lesson use motor more could I upgrade to a bigger 4 stroke say a 25hp n move around sufficiently ball park range on knots would be nice thanks
Motor use
- Thread starter Jaysway1
- Start date
Sailboats are displacement hulls, so the top speed is limited by the shape of the hull not the horsepower in the motor. If you search for "hull speed" you'll find a formula that will calculate the theoretical hull speed. A 23 foot boat will have a hull speed of around 5.5 to 6 knots or about 6 mph. That speed is speed through the water, not over ground.
A long shaft 8 HP motor will drive your boat easily in almost all conditions. Higher HP motors will add weight and torque to the transom which is not designed to support that weight and torque. It will also cause the boat to squat stern down. Running a 15 or 25 HP motor will simply make a lot of noise, affect the boats strength and integrity, and burn a lot of gas to go just as fast as it could with an 8 HP engine.
One of the factors with motor selection is the weight of the motor. When the O'Day was built outboards were almost universally 2 stroke motors. Two stroke outboards are significantly lighter than 4 stroke outboards. I would be hesitant to go above 8 HP. Years ago I had a 22 ft sailboat that weighed about 3000 lb with an 8 HP motor, it easily pushed the boat to hull speed at less than full throttle.
A long shaft 8 HP motor will drive your boat easily in almost all conditions. Higher HP motors will add weight and torque to the transom which is not designed to support that weight and torque. It will also cause the boat to squat stern down. Running a 15 or 25 HP motor will simply make a lot of noise, affect the boats strength and integrity, and burn a lot of gas to go just as fast as it could with an 8 HP engine.
One of the factors with motor selection is the weight of the motor. When the O'Day was built outboards were almost universally 2 stroke motors. Two stroke outboards are significantly lighter than 4 stroke outboards. I would be hesitant to go above 8 HP. Years ago I had a 22 ft sailboat that weighed about 3000 lb with an 8 HP motor, it easily pushed the boat to hull speed at less than full throttle.
I sail a Meridian 25, 4700 pounds loaded, 3.5 foot draft. I get hull speed with my 8 HP Yamaha running at the "start" setting'
The 8 hp tohatsu sailmaster would be a perfect fit for your Oday 23... checks all the boxes for power, weight, speed, economy and budget. Remote controls,electric start, power lift/trim and 12volt charging are features you can find if you move up to a 9.9hp or more. For your needs it may justify the added cost and weight (significant)… but that's a decision only you can make. For me, in my 27 footer, electric start remote control is most important. The motor essentially has the operational advantage of an inboard while retaining the maintenance convenience of an outboard.
This basic 8 hp tohatsu only weighs 83 lbs. 20 inch shaft (long). a few bucks more for 25" (extra long) if you need to mount off center because of rudder.
This basic 8 hp tohatsu only weighs 83 lbs. 20 inch shaft (long). a few bucks more for 25" (extra long) if you need to mount off center because of rudder.
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The 8 hp tohatsu sailmaster would be a perfect fit for your Oday 23... checks all the boxes for power, weight, speed, economy and budget. Remote controls,electric start, power lift/trim and 12volt charging are features you can find if you move up to a 9.9hp or more. For your needs it may justify the added cost and weight (significant)… but that's a decision only you can make. For me, in my 27 footer, electric start remote control is most important. The motor essentially has the operational advantage of an inboard while retaining the maintenance convenience of an outboard.
This basic 8 hp tohatsu only weighs 83 lbs. 20 inch shaft (long). a few bucks more for 25" (extra long) if you need to mount off center because of rudder.
Weight wise, the 8 and 9.9 weigh the same and are mostly the same engine. The difference being carb jetting and tuning. The same is true of the 4, 5, and 6 HP models. Tohatsu makes a lot of engines under different brands including Mercury and Nissan.
A 25 hp ob motor is quite a heavy beast. Not only would it be difficult to mount and remove it might put your boat stern down when you are sailing, changing your boat's sailing characteristics critically.
9.9 and 15 are often basically the same motor, but that's as high as that comparison goes. After that each engine get heavier without regard to the one below. Buying a reliable 25 (and mounting bracket strong enough to hold it on in bad weather) and the long shaft for a sailing boat and you'd do better financially getting the diesel fixed upfront.
9.9 and 15 are often basically the same motor, but that's as high as that comparison goes. After that each engine get heavier without regard to the one below. Buying a reliable 25 (and mounting bracket strong enough to hold it on in bad weather) and the long shaft for a sailing boat and you'd do better financially getting the diesel fixed upfront.
Some of the larger engines are impossible to tilt up with a normal motor mount. The cowling of my 9.9 would hit the transom whenever I tried. The 9.9 two stroke is adequate for my O'Day 25 which is around 5000lbs
@capta I think diesel inboards were featured on the O'Day 27's and larger. Ive seen the 15hp gas OMC Saildrives on the 25's and 28's. I'm guessing they were available on others as well
@capta I think diesel inboards were featured on the O'Day 27's and larger. Ive seen the 15hp gas OMC Saildrives on the 25's and 28's. I'm guessing they were available on others as well
Actually Tohatsu makes a 6 Hp called the sailpro... I have one and love it and it pushes my H26 at hull speed when only 3/4 throttle. It has a lower gear ratio, a high thrust prop and a 6A alternator.
It also is light enough that I can lift it with one arm.
It also is light enough that I can lift it with one arm.
Check your motor mount for weight capacity. Back then they use to rate motor mounts by horsepower which translated the average weight of a 2 stroke engine of the given maximum horsepower. Back then a 10 HP weighed around 60 lbs. You could always install a stronger motor mount but it all goes back to the weight that the boat can handle in the transom. Today a 4 stroke 8HP engine weighs around 80 lbs. and a 6 HP around 60 lbs. Neither of these two engines will propel you much beyond 6 knots in favorable conditions and the weight of a 25 HP engine would be out of the question for that boat.