what is the minimum HP I would need to power a 21 foot aluminum boat?

WIMUSKY

Moderator
Staff member
Joined
Sep 26, 2009
Messages
19,790
What max hp is the hull rated for, having that info will make for better suggestions......... Check the Capacity Plate...... Year would be nice too.....
 
Last edited:

Maranvin

Seaman Apprentice
Joined
Jan 29, 2017
Messages
41
How about docking with that small of a motor. Will it have enough torque to slow speed maneuver in a strong current or winds? Maybe with the right prop?
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
A smaller high thrust model motor would work, but the cost is not going to be cheap, so you don't gain anything. If the 40 runs OK try to find a 4 blade high thrust prop, you won't get anywhere fast, but you should have good control, that is unless the current is close the maximum hull speed.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,468
You'll want 80% to 100% of what the hull is rated to handle.

Ayuh,...... My personal rule of thumb is 80% to 300%,....

My Starcraft 221 Islander had a 140 hp that did 28 mph on a Great day,....
I dropped in a 205 hp, 'n now she'll do 43 mph any day of the week,....

My little ole Glastron Jet-Flite was rated for 60 hp,.....
At 1st, I bolted on an 80 hp, til I blew it up,....
Then went to a 135 hp tower of power,....
That little boat, literally Fly's,....

This is with the ole 80 hp, 'n an 11" pitched prop,...
Hada pump the throttle to Wot 3 times to get it to Jump outa the water,....
Later with the 135 hp, 'n a 21" pitched prop, it did that every time I mashed the throttle from an idle speed,....
f3551-1.jpg


Power trim finally tamed it into a sweet little water Rocket,...
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
Enough is good
More is better
And too much is just right
 

WIMUSKY

Moderator
Staff member
Joined
Sep 26, 2009
Messages
19,790
It would be nice if the OP checked in. He posted the ? and logged off......
 

pckeen

Commander
Joined
Jun 20, 2012
Messages
2,067
70% of Max hp seems to generally be the minimum, but the Chiefrains are light cabin cruisers, and lots came powered at about 60% of Max hp. 60% of Max hp is 100hp. 90hp would be the absolute bear minimum, and you'll be happier with a 115 or 120 hp outboard.
 
Top