should i fun at full throttle or 3/4

[joekr111]

Johnson 6 pushing a 23' sailboat. it takes about 30 min to get to good starting place to sail

 

[Capt'n Chris]

Re: should i fun at full throttle or 3/4

Most would think that would be about right.

 

[Jeep Man]

Re: should i fun at full throttle or 3/4

I have a dream.......that people would read what they post before hit the "send" button.

 

[joekr111]

Re: should i fun at full throttle or 3/4

is it better to run at full throttle in my Johnson 6 or is it better to run at 3/4 throttle

 

[NYBo]

Re: should i fun at full throttle or 3/4

It depends on whether 3/4 throttle gets you up to hull speed. If so, going full throttle is just wasting gas and wearing out your motor faster.

 

[veritas honus]

Re: should i fun at full throttle or 3/4

If you run "full" or wide open throttle everywhere you go, your motor isn't going to last very long. It will, of course, break down at the worst possible moment. Take your time. Enjoy just being on the water. Go easy on the motor and you may never have to paddle.

Safe and happy boating always!!!

 

[veritas honus]

Re: should i fun at full throttle or 3/4

I have a dream.......that people would read what they post before hit the "send" button.

 

[DaNinja]

Re: should i fun at full throttle or 3/4

I have a dream.......that people would read what they post before hit the "send" button.

It's a good dream...

 

[Boatist]

Re: should i fun at full throttle or 3/4

If I had to run full throttle to reach Hull speed I would upgrade to a 9.9 or 15HP
with a 4 blade 10 inch by 7 pitch high thrust prop and run at 1/2 throttle.

This motor and prop would back up much better and gain forward motion much faster.
Also run at hull speed without straining

 

[Capt'n Chris]

Re: should i fun at full throttle or 3/4

It depends on whether 3/4 throttle gets you up to hull speed. If so, going full throttle is just wasting gas and wearing out your motor faster.

"Hull speed"...great advice! Now, just how would the sailor with the question compute that?

 

[shrew]

Re: should i fun at full throttle or 3/4

"Hull speed"...great advice! Now, just how would the sailor with the question compute that?

Edit: Hull Speed

OR

Hull Speed = pi x (Square root of LWL)

LWL: Boat Length at Water Line
pi = 1.34


Here we have a length of 23 ft., however I suspect that is the total length. since we don't have a Length at waterline, we'll use total length.

Hull Speed = 1.34 x 4.795

Hull Speed = 6.42 MPH

You can also use a browser to find any number of sites with online Hull Speed Calculaters.

In short, if the current motor is pushing you at 6.42 MPH at 3/4 throttle, then there is no point in going to full throttle or even a larger motor. To attempt to exceed hull speed will mean that the boat is now attempting to climb out of the hole up on top of the bow wave and start planing (semi-displacement). The amount of HP and fuel to accomplish this works on a curve and it will take exponentially more HP and fuel for each 1/2 - 1 mile gained.

 

[tschmidty]

Re: should i fun at full throttle or 3/4

All good, but hull speed is actually knots not mph, but 6.5 mph is probably about right for that boat.

And it really is just a baseline and is based on a full displacement hull (like most sailboats). There are certainly sailboats that can get out of the hole and plane.

 

[geeco1]

Re: should i fun at full throttle or 3/4

http://www.google.com

OR

Hull Speed = pi x (Square root of LWL)

LWL: Boat Length at Water Line
pi = 1.34


Here we have a length of 23 ft., however I suspect that is the total length. since we don't have a Length at waterline, we'll use total length.

Hull Speed = 1.34 x 4.795

Hull Speed = 6.42 MPH

You can also use a browser to find any number of sites with online Hull Speed Calculaters.

In short, if the current motor is pushing you at 6.42 MPH at 3/4 throttle, then there is no point in going to full throttle or even a larger motor. To attempt to exceed hull speed will mean that the boat is now attempting to climb out of the hole up on top of the bow wave and start planing (semi-displacement). The amount of HP and fuel to accomplish this works on a curve and it will take exponentially more HP and fuel for each 1/2 - 1 mile gained.

Isn't pi = 3.14???

So hull speed would be 3.14 x 4.795 = approx 15.0

 

[Capt'n Chris]

Re: should i fun at full throttle or 3/4

http://www.google.comYes, Google can be a big help in the matter. Do you think he might be interested in or have the time in his 30 minute junket to compute something so inaccurate, or even care? If he is, wouldn't Bollard pull be a more appropriate to his motoring dilemma instead of calculating a most inaccurate "hull speed?"
OR

Hull Speed = pi x (Square root of LWL)

LWL: Boat Length at Water Line
pi = 1.34


Here we have a length of 23 ft., however I suspect that is the total length. since we don't have a Length at waterline, we'll use total length.

Hull Speed = 1.34 x 4.795

Hull Speed = 6.42 MPH

You can also use a browser to find any number of sites with online Hull Speed Calculaters.

In short, if the current motor is pushing you at 6.42 MPH at 3/4 throttle, then there is no point in going to full throttle or even a larger motor. To attempt to exceed hull speed will mean that the boat is now attempting to climb out of the hole up on top of the bow wave and start planing (semi-displacement). The amount of HP and fuel to accomplish this works on a curve and it will take exponentially more HP and fuel for each 1/2 - 1 mile gained.

Yes, Google can be a big help in the matter. Do you think he might be interested in or have the time in his 30 minute junket to compute something so inaccurate, or even care? If he is, wouldn't Bollard pull be more appropriate to his motoring dilemma instead of calculating a most inaccurate "hull speed?"

 

[tschmidty]

Re: should i fun at full throttle or 3/4

Opps didn't spot the PI error, but his number and calculation is correct. The hull speed calculation is pretty close.

The OP's question is whether he should run at full or 3/4 throttle. Others asked well how fast are you going at those throttle settings? Hull speed is entirely relevant. Bollard Pull is not. There is a reason sailboats are equipped with smaller motors for their size and it's not because sailors just want to go slow. It's because sailboats do not plane, which greatly increases horsepower requirements to the point where it is not worth it to try to push past hull speed. So you size your motor to get you at or close to hull speed at a cruising RPM and call it a day.

But we can just take the easy answer to the OP's question which is No, you shouldn't run your motor at full throtttle all the time. if 3/4 doesn't get you close to hull speed (6-7 MPH or so) then get a bigger motor or be satisfied going slower.

 

[Skiwi]

Re: should i fun at full throttle or 3/4

3/4 = better fuel economy, motor longevity and a quieter more relaxed trip

 

[DJ]

Re: should i fun at full throttle or 3/4

There is VERY little difference between FULL throttle and 3/4 on a 6 hp..

Full, burns a lot fuel, 3/4 does not.

Prop it right and realize the amazing things a 6 HP can do.