With a 21' boat most you will get with a kicker is about 6.5 mph. Is hull
speed. 7.5 hp will probably do maybe 5. My 21' boat with a High Thrust T-8
Yamaha will get the 6.5 mph, but with the standard thrust 15 Mariner would
do about 5.5 mph.
Bill

"DJ" wrote in message
...
"Jim" wrote in message ...
Hello,

Just got a 21ft, '01 Starcraft Islander aluminum hull and wanted to put
a kicker for trolling. Can a 7.5hp small outboard push this boat at
least 9mph or do I need bigger? Should I have the bracket installed
professionally or is this a DIY project? Boat is like new with 13hrs and
Im very weary on drilling holes into it..lol.

Any help would be appreciated...

Hi Jim: I don't know if this applies to your boat (I'm not familiar with
that hull), but it might help. From my experience, the 7.5 might work OK
for slow trolling, but I would guess that it wouldn't push it at 9 mph.
I'm
thinking a 10 or 15 might work better.

Background for comparison purposes: I have a 21 foot welded aluminum
runabout river boat - wide, flat bottom (6 foot), welded windshield,
covered
V bow, interior tanks w/ 50 gal capacity, canvas top, folding seats, etc.,
with a large V6 two stroke outboard. On the trailer, wet, it weighs about
3300 lbs, so I think the boat and motor wet is about 2300-2500 lbs.

I've been using an old 9.8 hp regular/short shaft Mercury and it works
very
well for trolling (we troll at 2-3 mph by GPS for coho salmon and lake
trout). I've also used it as a back up and it will hit maybe 5 or 6 mph
full speed which is OK for that purpose, but not great. I think long
shaft
will definitely work better on my boat. At the lowest bracket setting,
the
prop on this kicker of mine tends to be a little quick to ventilate (loose
bite) in the chop and/or if there's too much weight forward.

The motor is in excellent mechanical condition from compression to lower
unit, so I'm assuming performance is comparable to a newer 10 hp. The
prop
is a brass two blade in good condition- probably the original prop. I
have
no idea if a different prop would change performance. I'm keeping my eyes
open for a 15 hp long shaft because I think it would give me a little more
oomph at about the same weight and give me a better bite in certain
conditions.

As for the kicker bracket mounting - In my particular boat, it could
easily
be a DIY because I can easily see the structure that it would be mounted
to
and there's really no options as to placement. It would take a good drill
and reasonable care in marking and drilling the holes, but it would be
pretty straight forward I think. If I couldn't easily tell exactly where
to
mount it, or was pressed for time in any way, I wouldn't hesitate to take
it
to a pro because I don't think it would be a whole lot of "shop time" to
mount it - probably the minimum.

Before you procede, try to figure out if the kicker bracket will lower the
motor enough to work well with a regular/short shaft motor. Also give
thought to which side would be best, and how you'd hook up a remote
steering
system (I use the EZ Steer and love it). Then if you can borrow or rent a
7.5 or other, give it a try.

Have fun.

DJ