View Full Version : Running dual engines on small boat ok?

10-29-2005, 10:05 PM
I have a Boston Whaler 13 ft sport with a Yamaha 15 horse.
I have always wished for more power and have hatched an idea to buy a second motor, maybe an 8 horse for a safety backup on the seas. Will the boat steer okay with both motors running? Is it smart to think to think that a 15 and an 8 will make 23 horses worth of power?

10-29-2005, 11:06 PM
You can run two motors. But you probably won't be able to open up an 8hp and a 15hp at the same time. The 15 will overwhelm the 8. You'll be able to tell when the 8 is being overwhelmed because it will start over-revving as the prop starts slipping. That's why most folks that run two motors at top speed have two identical motors with identical props. If you had two 15hp motors, you would have around 30hp. Still putting a 15 and an 8 on your Whaler might be a good idea. It gives you a backup motor if one goes down. The 8 might troll a little better than th 15.. Larry

10-30-2005, 07:41 AM
You see this all the time in 3rd world countries. Make sure that you use 2 different brands of engines with colors that clash to get the true "local native fisherman" look. ;D

Actually, it is not a good idea to run 2 engines with very different hp ratings and propeller dimensions at full throttle. As Larry pointed out, the smaller engine will over rev unless you take pains to get the props just right. I have a friend in Alaska who ruined a Yamaha T-8 (yes it can be done) by running it at the same time as his 150 hp main engine. His rational was to get a few extra mph. What he got was bad bearings after only 1 season. That is an extreme case with very mismatched engines, but it illustrates the point.

10-30-2005, 08:07 AM
8)I would also have to mention that both motors running it might be hard to steer if one was not counter rotating, other wise you may only be able to turn to the right and very little left due to torque. 8)

10-30-2005, 09:16 AM
Like fishkiller said most twin powered boats have counter rotating props to control prop steer. Spend the money on a bigger single power motor.

10-31-2005, 09:42 AM
Can't you handle the steering problem by adjusting the rudder tab on the motor? That's what it's there for to correct for starboard or port helm.