|
Tender problem, maybe
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? |
Tender problem, maybe
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. |
Tender problem, maybe
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. |
Tender problem, maybe
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 |
Tender problem, maybe
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. |
Tender problem, maybe
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. |
Tender problem, maybe
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! |
Tender problem, maybe
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. |
Tender problem, maybe
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? |
Tender problem, maybe
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... |
Tender problem, maybe
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. |
Tender problem, maybe
On 6/5/2012 6:39 PM, JustWait wrote:
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. Yes. |
Tender problem, maybe
On 6/5/2012 6:30 PM, Tim wrote:
On Jun 5, 9:28 am, 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! My pleasure. |
Tender problem, maybe
|
Tender problem, maybe
On Jun 5, 8:17*pm, Oscar 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. |
Tender problem, maybe
On Tue, 05 Jun 2012 21:25:10 -0400, Oscar 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. |
Tender problem, maybe
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... |
Tender problem, maybe
On Jun 5, 10:40*pm, JustWait 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. |
Tender problem, maybe
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. Yes and no. I would like it to go faster but I'm not willing to throw more horses(and weight) at the problem. This thing gets packed away after almost each use so it needs to be relatively easy for me to set up nearly singlehanded. I'm not the musclebound hulk I used to be ;-) |
Tender problem, maybe
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. |
Tender problem, maybe
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.. |
Tender problem, maybe
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 |
Tender problem, maybe
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. :-) |
Tender problem, maybe
On Jun 6, 8:20*am, Oscar wrote:
I'm not the musclebound hulk I used to be ;-) Don't feel alone... |
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