20 hp?

If you put two 9.9s on does this classify as a 20?

ORIGINAL: Mikastorm

If you put two 9.9s on does this classify as a 20?

 
 
Nope it's only 19.8. LOL
Mike

I am curious now. Do you have two 9.9 and just for kicks and giggles put them on one boat?
 
If you were going to try to get more speed out of your boat it will not happen. Assuming if they were the same motor with the same pitch prop they can only go as fast as the theroritical top speed of one. so you might on paper gain a few mph but the added drag on two lower units in the water would take most of that away.
 
But i do not know the reasons but i know if i had two sitting around i would try it to see what will happen.

John, certainly you have something better to do with your time and $$$ don't you.   How've you been? didn't get to the Oil Creek outing this year & get to see some old friends......... Dave

ORIGINAL: anzomcik

I am curious now. Do you have two 9.9 and just for kicks and giggles put them on one boat?

If you were going to try to get more speed out of your boat it will not happen. Assuming if they were the same motor with the same pitch prop they can only go as fast as the theroritical top speed of one. so you might on paper gain a few mph but the added drag on two lower units in the water would take most of that away.

But i do not know the reasons but i know if i had two sitting around i would try it to see what will happen.

 
 
If that's the case then why do you see many off-shore salt water fishing boats with 2 and 3 outboards? They gotta be gaining mph and overall power.  

It has been proven that one 300 hp motor will outperform two 150hp motors. with the two motors you gain more weight use more fuel and have more drag. So i guess to answer your question i am not sure why i do not know but davef has a good point of may be a failure of one?
 
I have a 14 foot aluminum that had a 9.9 on it it would go 8mph with my gear, and fishing partner (maybe 9mph alone). i have a tach for the motor it would only rev to 3800rpm on a good day ( i tryed different pitch props with little success maybe 1+ mph) so i worked it out the 9.9 top speed on paper in perfect world would be almost 18mph. By adding another motor that can only do 18mph your boat can only do 18mph perfect world on paper.
 
A year ago i ditched the 9.9 and got a 25 hp mariner ( i know it isnt 20 like the topic but for the sake of the discussion) my personal best in my boat is 28mph, but on any day of the week loaded with gear and and fishing partner it will scoot at 24mph. It take 13mph to put my boat on plane i have not tried but i think two 9.9s could not do that.
 
With the big off shore boats the resistance from another LU in the water when pushed with a 90+ hp motor the percent of power it takes away from performance is smaller than that of a 9.9 trying to do the same. Those are my thoughts i have not done it i cant give hard numbers just compair them to what i have done

If you do give it a whirl don't do what I did when we put 2 electric motors on my boat.
 
We wanted a little more thrust so we put 2 electrics side by side. Gained a little speed over one motor. Got to the Crappie pack a little faster.
But when we went to anchor I didn't get the one motor clicked all the way off and the **** boat kept going around in circles no matter how we set the anchors.
 
We even started insinuating to each other what are you too **** stupid to run an anchor...I think we were comic relief for the 40 or so boats that got to watch our antics...

Most offshore boats with twins won't get on plane with only a single motor in operation.  Trips and quads are for one thing, speed.  Probably is better from an efficiency standpoint to run one 300 hp in lieu of 2 150 hp but, the safety factor greatly outweighs the gains in efficiency for the offshore saltwater guys when they are running 50 to 100 miles offshore.  You won't get on plane with a single motor and may not even make it all the way back in on one motor in heavy seas (due to excess fuel burn) but you will get a lot closer than if that single 300 hp motor went out on you.  That being said, me and my buddy down there regulary went 40+ miles offshore in his 21' Sea Chaser C.C. with a single 150 hp Yamaha.   

2 motors are better than one due to safty factor a single moter will get a better fuel savings but as was said 2motors will give more control in rough seas thus i would want 2 150s instead of 1 300hp option b is always a motor on the side for a kicker i had a 25hp on a 22ft cruisers and it moved the boat in 2-4ft ok went to a long shaft 35 and it just bit a little water and yes mounted on swim platform made a bracket and now no longer use it i should sell the thing

2000HP! Dang Skip ya trying to get rid of me! lol

hay where is the fuel hose to the tanker to feed all those moters gulp gulp gals per foot  

When using two outboards you need counter rotating props. One spins clock wise one counter.