The facts:
9'X5' inflatable with inflatable keel and hard floor.
5hp 4 stroke engine.
7 1/2 X 7 3 blade prop.

Here's what's happening:
Engine runs smooth as silk.
At about 1/2 throttle GPS measures 4 1/2 MPH
At full throttle GPS measures a little over 5MPH
There is no noticeable change in pitch or DB between 1/2 and full throttle.
Engine doesn't seem to be bogging down.
Speed increase between 1/2 and full throttle is gradual even though
throttle is advanced quickly.
Boat bottom is clean.
Prop is in excellent shape.

Questions:
Is this normal?
Should I try a lower pitched prop?
Do I need more Horsepower?
What do you think?

On 6/5/2012 10:28 AM, Oscar wrote:
The facts:
9'X5' inflatable with inflatable keel and hard floor.
5hp 4 stroke engine.
7 1/2 X 7 3 blade prop.

Here's what's happening:
Engine runs smooth as silk.
At about 1/2 throttle GPS measures 4 1/2 MPH
At full throttle GPS measures a little over 5MPH
There is no noticeable change in pitch or DB between 1/2 and full throttle.
Engine doesn't seem to be bogging down.
Speed increase between 1/2 and full throttle is gradual even though
throttle is advanced quickly.
Boat bottom is clean.
Prop is in excellent shape.

Questions:
Is this normal?
Should I try a lower pitched prop?
Do I need more Horsepower?
What do you think?

Hull speed is hull speed. At a point a boat will just not go any faster
no matter how much power you put to it, until you break the bow wave and
go on plane... Without doing the calculations, 4 1/2 sounds about dead
on for "hull speed" on the soft sided, hard bottom raft.

On 6/5/2012 10:36 AM, JustWait wrote:
On 6/5/2012 10:28 AM, Oscar wrote:
The facts:
9'X5' inflatable with inflatable keel and hard floor.
5hp 4 stroke engine.
7 1/2 X 7 3 blade prop.

Here's what's happening:
Engine runs smooth as silk.
At about 1/2 throttle GPS measures 4 1/2 MPH
At full throttle GPS measures a little over 5MPH
There is no noticeable change in pitch or DB between 1/2 and full
throttle.
Engine doesn't seem to be bogging down.
Speed increase between 1/2 and full throttle is gradual even though
throttle is advanced quickly.
Boat bottom is clean.
Prop is in excellent shape.

Questions:
Is this normal?
Should I try a lower pitched prop?
Do I need more Horsepower?
What do you think?

Hull speed is hull speed. At a point a boat will just not go any faster
no matter how much power you put to it, until you break the bow wave and
go on plane... Without doing the calculations, 4 1/2 sounds about dead
on for "hull speed" on the soft sided, hard bottom raft.

Thanks. I suspect you are right.

On Tue, 05 Jun 2012 10:28:52 -0400, Oscar wrote:

The facts:
9'X5' inflatable with inflatable keel and hard floor.
5hp 4 stroke engine.
7 1/2 X 7 3 blade prop.

Here's what's happening:
Engine runs smooth as silk.
At about 1/2 throttle GPS measures 4 1/2 MPH
At full throttle GPS measures a little over 5MPH
There is no noticeable change in pitch or DB between 1/2 and full throttle.
Engine doesn't seem to be bogging down.
Speed increase between 1/2 and full throttle is gradual even though
throttle is advanced quickly.
Boat bottom is clean.
Prop is in excellent shape.

Questions:
Is this normal?
Should I try a lower pitched prop?
Do I need more Horsepower?
What do you think?

===

As others have mentioned, you are running up against the hull speed of
the dinghy and don't have enough power to get on plane. My
experience with inflatables is that you need at least 8 or 9 hp to get
on plane with 2 adults, and 15 hp is even better. A Doel-Fin on the
outboard is also a big help.

I assume you have a rigid transom? If so it should have a
manufacturers plate somewhere which states your max horsepower rating.
That's usually about the right number for everyday use.

http://www.basspro.com/Doel-fin-Hydrofoil-Stabilizer/product/27337/88162?hvarAID=shopping_googlebase&om_mmc=shopping_ googlebase

On 6/5/2012 4:38 PM, Wayne.B wrote:
On Tue, 05 Jun 2012 10:28:52 -0400, wrote:

The facts:
9'X5' inflatable with inflatable keel and hard floor.
5hp 4 stroke engine.
7 1/2 X 7 3 blade prop.

Here's what's happening:
Engine runs smooth as silk.
At about 1/2 throttle GPS measures 4 1/2 MPH
At full throttle GPS measures a little over 5MPH
There is no noticeable change in pitch or DB between 1/2 and full throttle.
Engine doesn't seem to be bogging down.
Speed increase between 1/2 and full throttle is gradual even though
throttle is advanced quickly.
Boat bottom is clean.
Prop is in excellent shape.

Questions:
Is this normal?
Should I try a lower pitched prop?
Do I need more Horsepower?
What do you think?

===

As others have mentioned, you are running up against the hull speed of
the dinghy and don't have enough power to get on plane. My
experience with inflatables is that you need at least 8 or 9 hp to get
on plane with 2 adults, and 15 hp is even better. A Doel-Fin on the
outboard is also a big help.

I assume you have a rigid transom? If so it should have a
manufacturers plate somewhere which states your max horsepower rating.
That's usually about the right number for everyday use.

http://www.basspro.com/Doel-fin-Hydrofoil-Stabilizer/product/27337/88162?hvarAID=shopping_googlebase&om_mmc=shopping_ googlebase

I doubt they make doel fins small enough.
I suspected HP was the problem and you guys confirmed it.
I suppose the best thing to do is use just enough throttle to drive it
to hull speed and be satisfied.
thanks for your input.

On Jun 5, 5:10*pm, Oscar wrote:
On 6/5/2012 4:38 PM, Wayne.B wrote:









On Tue, 05 Jun 2012 10:28:52 -0400, *wrote:

The facts:
9'X5' inflatable with inflatable keel and hard floor.
5hp 4 stroke engine.
7 1/2 X 7 3 blade prop.

Here's what's happening:
Engine runs smooth as silk.
At about 1/2 throttle GPS measures 4 1/2 MPH
At full throttle GPS measures a little over 5MPH
There is no noticeable change in pitch or DB between 1/2 and full throttle.
Engine doesn't seem to be bogging down.
Speed increase between 1/2 and full throttle is gradual even though
throttle is advanced quickly.
Boat bottom is clean.
Prop is in excellent shape.

Questions:
Is this normal?
Should I try a lower pitched prop?
Do I need more Horsepower?
What do you think?

===

As others have mentioned, you are running up against the hull speed of
the dinghy and don't have enough power to get on plane. * My
experience with inflatables is that you need at least 8 or 9 hp to get
on plane with 2 adults, and 15 hp is even better. *A Doel-Fin on the
outboard is also a big help.

I assume you have a rigid transom? *If so it should have a
manufacturers plate somewhere which states your max horsepower rating.
That's usually about the right number for everyday use.

http://www.basspro.com/Doel-fin-Hydrofoil-Stabilizer/product/27337/88....

I doubt they make doel fins small enough.
I suspected HP was the problem and you guys confirmed it.
I suppose the best thing to do is use just enough throttle to drive it
to hull speed and be satisfied.
thanks for your input.

But i you could get at least a 10-12 and put on it, I'd say you'd
bemore pleased with it's obvious performance, but also better fuel
economy per a set distance.

On Jun 5, 9:28*am, Oscar wrote:
The facts:
9'X5' inflatable with inflatable keel and hard floor.
5hp 4 stroke engine.
7 1/2 X 7 3 blade prop.

Here's what's happening:
Engine runs smooth as silk.
At about 1/2 throttle GPS measures 4 1/2 MPH
At full throttle GPS measures a little over 5MPH
There is no noticeable change in pitch or DB between 1/2 and full throttle.
Engine doesn't seem to be bogging down.
Speed increase between 1/2 and full throttle is gradual even though
throttle is advanced quickly.
Boat bottom is clean.
Prop is in excellent shape.

Questions:
Is this normal?
Should I try a lower pitched prop?
Do I need more Horsepower?
What do you think?

BTW Oscar, thanks for the boating topic!

On 6/5/2012 6:10 PM, Oscar wrote:
On 6/5/2012 4:38 PM, Wayne.B wrote:
On Tue, 05 Jun 2012 10:28:52 -0400, wrote:

The facts:
9'X5' inflatable with inflatable keel and hard floor.
5hp 4 stroke engine.
7 1/2 X 7 3 blade prop.

Here's what's happening:
Engine runs smooth as silk.
At about 1/2 throttle GPS measures 4 1/2 MPH
At full throttle GPS measures a little over 5MPH
There is no noticeable change in pitch or DB between 1/2 and full
throttle.
Engine doesn't seem to be bogging down.
Speed increase between 1/2 and full throttle is gradual even though
throttle is advanced quickly.
Boat bottom is clean.
Prop is in excellent shape.

Questions:
Is this normal?
Should I try a lower pitched prop?
Do I need more Horsepower?
What do you think?

===

As others have mentioned, you are running up against the hull speed of
the dinghy and don't have enough power to get on plane. My
experience with inflatables is that you need at least 8 or 9 hp to get
on plane with 2 adults, and 15 hp is even better. A Doel-Fin on the
outboard is also a big help.

I assume you have a rigid transom? If so it should have a
manufacturers plate somewhere which states your max horsepower rating.
That's usually about the right number for everyday use.

http://www.basspro.com/Doel-fin-Hydrofoil-Stabilizer/product/27337/88162?hvarAID=shopping_googlebase&om_mmc=shopping_ googlebase


I doubt they make doel fins small enough.
I suspected HP was the problem and you guys confirmed it.
I suppose the best thing to do is use just enough throttle to drive it
to hull speed and be satisfied.
thanks for your input.

You are correct, and that is exactly what the boat is designed for... If
you want to go faster, get the right boat.

On 6/5/12 6:26 PM, Tim wrote:
On Jun 5, 5:10 pm, wrote:
On 6/5/2012 4:38 PM, Wayne.B wrote:









On Tue, 05 Jun 2012 10:28:52 -0400, wrote:

The facts:
9'X5' inflatable with inflatable keel and hard floor.
5hp 4 stroke engine.
7 1/2 X 7 3 blade prop.

Here's what's happening:
Engine runs smooth as silk.
At about 1/2 throttle GPS measures 4 1/2 MPH
At full throttle GPS measures a little over 5MPH
There is no noticeable change in pitch or DB between 1/2 and full throttle.
Engine doesn't seem to be bogging down.
Speed increase between 1/2 and full throttle is gradual even though
throttle is advanced quickly.
Boat bottom is clean.
Prop is in excellent shape.

Questions:
Is this normal?
Should I try a lower pitched prop?
Do I need more Horsepower?
What do you think?

===

As others have mentioned, you are running up against the hull speed of
the dinghy and don't have enough power to get on plane. My
experience with inflatables is that you need at least 8 or 9 hp to get
on plane with 2 adults, and 15 hp is even better. A Doel-Fin on the
outboard is also a big help.

I assume you have a rigid transom? If so it should have a
manufacturers plate somewhere which states your max horsepower rating.
That's usually about the right number for everyday use.

http://www.basspro.com/Doel-fin-Hydrofoil-Stabilizer/product/27337/88...

I doubt they make doel fins small enough.
I suspected HP was the problem and you guys confirmed it.
I suppose the best thing to do is use just enough throttle to drive it
to hull speed and be satisfied.
thanks for your input.

But i you could get at least a 10-12 and put on it, I'd say you'd
bemore pleased with it's obvious performance, but also better fuel
economy per a set distance.


Oscar has a friend with a boat?

On 6/5/2012 6:26 PM, Tim wrote:
On Jun 5, 5:10 pm, wrote:
On 6/5/2012 4:38 PM, Wayne.B wrote:









On Tue, 05 Jun 2012 10:28:52 -0400, wrote:

The facts:
9'X5' inflatable with inflatable keel and hard floor.
5hp 4 stroke engine.
7 1/2 X 7 3 blade prop.

Here's what's happening:
Engine runs smooth as silk.
At about 1/2 throttle GPS measures 4 1/2 MPH
At full throttle GPS measures a little over 5MPH
There is no noticeable change in pitch or DB between 1/2 and full throttle.
Engine doesn't seem to be bogging down.
Speed increase between 1/2 and full throttle is gradual even though
throttle is advanced quickly.
Boat bottom is clean.
Prop is in excellent shape.

Questions:
Is this normal?
Should I try a lower pitched prop?
Do I need more Horsepower?
What do you think?

===

As others have mentioned, you are running up against the hull speed of
the dinghy and don't have enough power to get on plane. My
experience with inflatables is that you need at least 8 or 9 hp to get
on plane with 2 adults, and 15 hp is even better. A Doel-Fin on the
outboard is also a big help.

I assume you have a rigid transom? If so it should have a
manufacturers plate somewhere which states your max horsepower rating.
That's usually about the right number for everyday use.

http://www.basspro.com/Doel-fin-Hydrofoil-Stabilizer/product/27337/88...

I doubt they make doel fins small enough.
I suspected HP was the problem and you guys confirmed it.
I suppose the best thing to do is use just enough throttle to drive it
to hull speed and be satisfied.
thanks for your input.

But i you could get at least a 10-12 and put on it, I'd say you'd
bemore pleased with it's obvious performance, but also better fuel
economy per a set distance.

I am not sure which model he has but if it's a raft like mine, it won't
hold a bigger motor, it will just bend the boat in half... If it's a
"Zodiac Type" boat with shaped sides and nose, maybe...