On 6/6/2012 8:44 AM, Tim wrote:
On Jun 5, 10:40 pm, wrote:
On 6/5/2012 11:13 PM, Tim wrote:









On Jun 5, 8:17 pm, wrote:
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.

Reality is Tim, that the boat is performing within its design parameters
and I'm good with that.

Ok. I was thinking you were wanting more performance out of it-
something to push the hull out of the water.

It really depends on what kind of softside it is... If it's designed for
planing fine, but my seveylor didn't have enough stiffness and the
ingegrated motor mount wouldn't support anything more than three or four
horse. I bent one motormount with an 8 horse before the boat ever got on
plane...

When i read ti had a keel and hard floor. I thought it was a more
rigid type craft. I dont' know much of anything about inflatables.

Still could be that type, but I didn't catch it in the original
description..

On 6/6/2012 9:50 AM, JustWait wrote:
On 6/6/2012 8:44 AM, Tim wrote:
On Jun 5, 10:40 pm, wrote:
On 6/5/2012 11:13 PM, Tim wrote:









On Jun 5, 8:17 pm, wrote:
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.

Reality is Tim, that the boat is performing within its design
parameters
and I'm good with that.

Ok. I was thinking you were wanting more performance out of it-
something to push the hull out of the water.

It really depends on what kind of softside it is... If it's designed for
planing fine, but my seveylor didn't have enough stiffness and the
ingegrated motor mount wouldn't support anything more than three or four
horse. I bent one motormount with an 8 horse before the boat ever got on
plane...

When i read ti had a keel and hard floor. I thought it was a more
rigid type craft. I dont' know much of anything about inflatables.

Still could be that type, but I didn't catch it in the original
description..

It's not a RIB

On Wed, 06 Jun 2012 09:26:03 -0400, Oscar wrote:

On 6/5/2012 11:14 PM, Wayne.B wrote:
On Tue, 05 Jun 2012 21:25:10 -0400, wrote:

I'm positive that WOT RPM is way too low.

===

In that case a prop with lower pitch is the right way to go. At least
the motor will be operating within its designed range and you might be
able to get on plane if you're really lightly loaded.


You almost have me convinced to put a different prop on it. If I do, I
will Tach it first like someone else suggested.

===

I put a lower pitch prop and a Doel-fin on our Honda 4 stroke and it
made all the difference in the world. As a bonus you end up with a
spare prop. :-)

On Jun 6, 8:20*am, Oscar wrote:

I'm not the musclebound hulk I used to be ;-)

Don't feel alone...