Hello all. I have a 2006 Hunter 33 with 161 hours on engine. I just changed from the 3 blade fixed prop to a 2 blade gori, 16.5 x 13 x 1, and have noticed significant vibration now at different rpms. At the dock, reving up to max rpm, I get no vibration. I had a Yanmar specialist check out the mounts, shaft, alignment, and all looks good. I also talked to the dealer I bought the prop from, and they indicated that I would feel more vibration from a 2 blade than a 3 blade. Also, at 2000 rpm, in calm weather, the boat moves close to 6 knots, so I don't believe I am underpowered. Under sail, I am getting 1/2 knot to a full knot increase in speed over the 3 blade, so obviously I am happy about that. What else can I look for, or is this normal? Thanks, Mike
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What's your engine? 2 or 3 Cyl?
When you accelerate the engine at the dock is it in gear or not? You may not be underpowered but you could be overpropped. How did you measure your speed? Over water or over ground? As a general rule, engines will behave different when accelerated in neutral than when accelerated under load. It is true that a two blade prop may induce more vibration than that produced by a three blade one. It's hard to say without knowing your engine but seems to me that if you measured your speed with a knot meter (over water) and you are getting 6 knots out of 2000 RPM you could be overpropped. What is your maximum RPM reading at wide opn throtle. Most of these engines produce their maximum horsepower at around 3,400 RPM. They can rev a little higher but HP drops. What is the maximum RPM you attain at wide open throttle? If you do not get close to 3,400 you are overpropped and yes the added load on the engine can make it vibrate. Make sure your tachometer is well calibrated. Check with Hunter to see what size prop and pitch they recommend for the h33 and your particular engine.
When you accelerate the engine at the dock is it in gear or not? You may not be underpowered but you could be overpropped. How did you measure your speed? Over water or over ground? As a general rule, engines will behave different when accelerated in neutral than when accelerated under load. It is true that a two blade prop may induce more vibration than that produced by a three blade one. It's hard to say without knowing your engine but seems to me that if you measured your speed with a knot meter (over water) and you are getting 6 knots out of 2000 RPM you could be overpropped. What is your maximum RPM reading at wide opn throtle. Most of these engines produce their maximum horsepower at around 3,400 RPM. They can rev a little higher but HP drops. What is the maximum RPM you attain at wide open throttle? If you do not get close to 3,400 you are overpropped and yes the added load on the engine can make it vibrate. Make sure your tachometer is well calibrated. Check with Hunter to see what size prop and pitch they recommend for the h33 and your particular engine.
the engine is yanmar 3ym30. 3 cylinder, 29 horse. I was out of gear at the dock. My speed was measured with the knotmeter on the boat, and max rpm at full throttle is 3600. The prop is a gori 2 blade folder.
vibration
Since your boat is a 2006 with 161 hours I really doubt that it is the cutless bearing. 2-blade props are just more prone to vibration.
Since your boat is a 2006 with 161 hours I really doubt that it is the cutless bearing. 2-blade props are just more prone to vibration.
Mike, not normal
I have a two blade Gori, vibration is minnor, mostly buzzing sounds rather than shaking. Im stumped, would have said cutlass, except, as others have pointed out, low shaft hours.I have about 500 hours on my cutlass.
I have a two blade Gori, vibration is minnor, mostly buzzing sounds rather than shaking. Im stumped, would have said cutlass, except, as others have pointed out, low shaft hours.I have about 500 hours on my cutlass.
Mike, did I miss something?
I was looking for your description of the vibration. Can you be more specific?
I was looking for your description of the vibration. Can you be more specific?
the vibration can be described as the boat literally shaking when rpms are increased. Lifelines shake, overhead speaker assembly on the arch shakes, and the aft pulpit vibrates. Also increased noise that I never had before from the engine. I am going to send Hunter tech support an email on Monday. Maybe this prop is not suited for this boat, but the Gori people were the ones who spec'd it out.
if all you did
if all you did was change the prop, and the old prop worked fine, then the prop must be out of balance. In today's world on a new boat, just because it's a 2 blade prop is no excuse for the lifelines to shake. Plus, you'll wipe out your cutlass bearing in no time. Perhaps something is jamming one of the blades of the prop from opeing fully? This would cause a great deal of imbalance. I can't reccomend a good way to check this out without a diver or hauling.
if all you did was change the prop, and the old prop worked fine, then the prop must be out of balance. In today's world on a new boat, just because it's a 2 blade prop is no excuse for the lifelines to shake. Plus, you'll wipe out your cutlass bearing in no time. Perhaps something is jamming one of the blades of the prop from opeing fully? This would cause a great deal of imbalance. I can't reccomend a good way to check this out without a diver or hauling.
Yep, not right.
I loved my Gori. They are hard to install wrong, but. I'd be hauling out as soon as the dealer can meet at the travel lift. Usually a trunk-monkey can get the blades properly installed, but if a tooth is off one notch, that'll do what yours is doing. Another possibility is that the hub isn't seated on the shaft taper. (hub canted) Or the shaft wasn't cut off enough. That would cause the hub to not properly seat too. Sorry, no choice but to haul. I doubt it's an actual bad balance job. These things are made with too much precision to be that far out of balance. Even if they didn't balance them at all, they wouldn't operate as bad as yours. Keep us posted. P.S. Go VERY slowly to the haulout to avoid damaging your prop. It's entirely fixable once it's installed RIGHT.
I loved my Gori. They are hard to install wrong, but. I'd be hauling out as soon as the dealer can meet at the travel lift. Usually a trunk-monkey can get the blades properly installed, but if a tooth is off one notch, that'll do what yours is doing. Another possibility is that the hub isn't seated on the shaft taper. (hub canted) Or the shaft wasn't cut off enough. That would cause the hub to not properly seat too. Sorry, no choice but to haul. I doubt it's an actual bad balance job. These things are made with too much precision to be that far out of balance. Even if they didn't balance them at all, they wouldn't operate as bad as yours. Keep us posted. P.S. Go VERY slowly to the haulout to avoid damaging your prop. It's entirely fixable once it's installed RIGHT.
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