Hello, I have a problem ... I would like to know if this is one or if my boat is normal ... I just bought it. I just did the antifouling again. I even sanded the hull before doing so. But ... At 2800 rpm, I am at 6 knots. On my other ship, with the same engine, I was at 6 knots at 2000 rpm. Would I have a problem with my gearbox maybe Thank you in advance !!!!
My Hunter 380 is not moving! He is slow! It's normal?
- Thread starter GALIOSTRO
- Start date
What was the other boat? You can figure theoretical hull speed with this formula. HS = 1.34 * Square root ( Waterline length). Sooo, according to sailboatdata.com the LWL of the 380 is 32'. HS = 1.34 * square root (32) or 7.58 Kts. The Yanmar engine for your boat can probably turn around 3200 rpm. You may need that to push the boat at hull speed. Hunters are pretty wide and they need more power to push them then a narrower more easily driven hull.
HS = 1.34 x √LWL [where LWL=waterline length in feet (for a Hunter 380 LWL =32 feet)]
1.34 x √32 = 7.58 knots
Looks like you are slow.
Undersized propeller, oversized propeller, inefficient pitch, gearing, I'm not an engine guy, so I can't suggest any mechanical issues to consider.
I do know there are plenty of knowledgable sailors who will be along soon to help you.
Good luck.
-Will (Dragonfly)
1.34 x √32 = 7.58 knots
Looks like you are slow.
Undersized propeller, oversized propeller, inefficient pitch, gearing, I'm not an engine guy, so I can't suggest any mechanical issues to consider.
I do know there are plenty of knowledgable sailors who will be along soon to help you.
Good luck.
-Will (Dragonfly)
I just calibrated the tach on my Hunter 38. It was 500 rpms fast, meaning that the installed tach read 2400 while the handheld read 1900. Maybe not your problem, but with a new-to-you boat, it wouldn't hurt to check it.
That’s a good list of possibilities to which I’d add an inaccurate knotmeter. Start by checking the easy stuff (to fix) first
Props are expensive. Compare your knotmeter to GPS first maybe. You may not be that slow. It could be the prop, but do the cheap checks first.
Hello and thank you for your answers. I checked the speed with the GPS before writing to you. It's OK. The lap count too, OK. The propeller is a three blade. When the boat was dirty, it moved like a clean hull! This is the thing that intrigues me. Otherwise the propeller was also checked during the refit. on the other hand, what I forgot to ask is if it was suitable for the boat ... Because it is not the original one which was a twin blade.
My Hunter 386 also came with a 2 blade fixed prop. Replaced it with a 3 blade prop for higher speed. Sounds like kenvail has the right approach.
Today i send a mail to France Helice. This french company work on my propeller. I ask them if the propeller is the good size for my boat. I wait it....
My H356 has a two balade propeller. AT 2800rpm on a yanmar 3gm30 is where the power and consommation curves meet. So this is about thé best cruising speed. My GPS speed is 6knots on flat water. I would like a kiwiprop 3 blade for better 'performance' but not a lot more speed.
Galiostro, You are identifying the right areas to check. Prop, Tach, prop pitch, bottom. This assumes under power.
How is the boat sailing?
A 3 blade will provide improved thrust under power, while a 2 bladed prop will reduce drag while sailing. This improved thrust comes at compromise, sailing speed. You may have more power in the engine but the prop pitch is too high. So your prop digs into the water while pulling the stern down causing more drag slower speed. You need to consider all of the elements in putting the best prop system in the water.
Finally, no info on how the boat is loaded.
Your old boat. Did you have as much water, fuel and gear on the old boat as you have on the new boat?
If you are loaded to go on a 3 month cruise you will be slower and deeper in the water than if you are prepared to go for a day sail race with nothing in the boat except the crew and minimal weight.
How is the boat sailing?
A 3 blade will provide improved thrust under power, while a 2 bladed prop will reduce drag while sailing. This improved thrust comes at compromise, sailing speed. You may have more power in the engine but the prop pitch is too high. So your prop digs into the water while pulling the stern down causing more drag slower speed. You need to consider all of the elements in putting the best prop system in the water.
Finally, no info on how the boat is loaded.
Your old boat. Did you have as much water, fuel and gear on the old boat as you have on the new boat?
If you are loaded to go on a 3 month cruise you will be slower and deeper in the water than if you are prepared to go for a day sail race with nothing in the boat except the crew and minimal weight.