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Old 16-07-2015, 09:33   #1
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Pull to port under power

Hi all,
I have a contract on a boat and had a sea trial/survey yesterday. Under sail, she sails beautifully and tracks straight with little attention needed on the helm, however, under power, she pulls to port. The amount of resistance on the helm increase as the RPM's increase. Put it in neutral, she tracks straight. Back in gear, pull to port. She has a three blade MaxProp that could be over-pitched (black smoke at higher RPM's and doesn't reach full throttle).
Do you think it's the prop? How about the shaft alignment?

Thanks,
Tom
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Old 16-07-2015, 09:41   #2
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Re: Pull to port under power

For some boats it is normal and not really correctable. A Cal 34 I sailed on we would always put on the autopilot while motoring due to the pull under power.

Propeller walk happens in forward as well as reverse.

https://en.wikipedia.org/wiki/Propeller_walk
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Old 16-07-2015, 09:45   #3
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Re: Pull to port under power

HI that is a common occurance on many boats, caused I believe by prop walk. Ole
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Old 16-07-2015, 09:59   #4
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Re: Pull to port under power

Ya, that's more than likely you're three bladed prop, on the plus, when you want power you have it now not later, I have a meaty 3 bladed prop and wouldn't change it for the world- I like bite.

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Old 16-07-2015, 10:04   #5
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Re: Pull to port under power

Thanks for the quick responses. Apparently, according to the broker who deals with many of these models, it is not indicative of the model, so it must be related to this individual boat and most likely, the prop. So if I read that Wikipedia article correctly, the clearance between the tips of the prop and the hull could increase this action? Maybe the prop's diameter is too large as well as over-pitched? I didn't think to measure the diameter of the prop nor the clearance dimensions. The current owner was there and he said that this has always been the situation but he also said he had the dealer switch from a fixed prop to the Maxprop during commissioning.
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Old 16-07-2015, 10:05   #6
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Re: Pull to port under power

That's propwalk, which is typical and is to be expected. I doubt any change to the propeller will eliminate it. Going forward under power, I need to angle the rudder 3 degrees to counter it.
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Old 16-07-2015, 10:07   #7
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Re: Pull to port under power

In addition to prop walk some boats are set up with the engine and shaft slightly off center. This may be done to allow the prop shaft to be pulled past the rudder or skeg. Once the boat is moving you wouldn't notice it but at very low speed it can be felt.


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Old 16-07-2015, 10:25   #8
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Re: Pull to port under power

Yes, this is prop walk. It might be possible to reduce it with a prop change (and the idea of increased the clearance between prop and hull is a good one).

The first thing, though, is try to get used to it.

I tend to apply a little, not too much, wheel brake when motoring. Just enough to make the wheel stay put. I can still turn the wheel to make course corrections. When sailing I take the brake off altogether.
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Old 16-07-2015, 10:35   #9
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Re: Pull to port under power

Almost all of the vessels I have owned, I over ran an oversize prop. Single or twin. The advantage is economy. By running the engine slower you save as much as 50%. while loosing only a couple knots in speed.
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Old 16-07-2015, 10:36   #10
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Re: Pull to port under power

Quote:
Originally Posted by Tortuga's Lie View Post

1 Apparently, according to the broker who deals with many of these models, it is not indicative of the model, so it must be related to this individual boat and most likely, the prop.

2 The current owner was there and he said that this has always been the situation but he also said he had the dealer switch from a fixed prop to the Maxprop during commissioning.
1 Doubt it. Most ALL boats have prop walk in forward under cruising rpms.

2 He oughta know.
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Old 16-07-2015, 10:39   #11
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Re: Pull to port under power

Quote:
Originally Posted by Tortuga's Lie View Post
Hi all,
I have a contract on a boat and had a sea trial/survey yesterday. Under sail, she sails beautifully and tracks straight with little attention needed on the helm, however, under power, she pulls to port. The amount of resistance on the helm increase as the RPM's increase. Put it in neutral, she tracks straight. Back in gear, pull to port. She has a three blade MaxProp that could be over-pitched (black smoke at higher RPM's and doesn't reach full throttle).
Do you think it's the prop? How about the shaft alignment?

Thanks,
Tom
What kind of engine is it, and what was the maximum rpm you could reach?
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Old 16-07-2015, 11:16   #12
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Re: Pull to port under power

Quote:
Originally Posted by Stu Jackson View Post
1 Doubt it. Most ALL boats have prop walk in forward under cruising rpms.

2 He oughta know.
My current boat has no forward prop walk, only reverse walk to port and yes, the current owner kind of shrugged it off basically saying that you get used to it....
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Old 16-07-2015, 11:18   #13
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Re: Pull to port under power

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What kind of engine is it, and what was the maximum rpm you could reach?
The engine is a Yanmar 4jh4-te and it made it up to 3300 rpms, which I guess should be 3600 rpms.....
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Old 16-07-2015, 11:31   #14
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Re: Pull to port under power

I have that same engine, the same prop, and the tartan 4100. It pulls to port because the prop shaft is slightly offset of center when exiting the hull. It is normal to all tartan 4100s with the shaft drive, and it will not cause you any trouble. The three blade prop in that position with the huge rudder means you can back down into any slip or space, even in contrary wind and current. Being able to steer easily and straight in reverse means you are driving the boat from a foot away from the end instead of trying to see a bow that is 40 feet ahead of you
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Old 16-07-2015, 11:35   #15
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Re: Pull to port under power

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I have that same engine, the same prop, and the tartan 4100. It pulls to port because the prop shaft is slightly offset of center when exiting the hull. It is normal to all tartan 4100s with the shaft drive, and it will not cause you any trouble. The three blade prop in that position with the huge rudder means you can back down into any slip or space, even in contrary wind and current. Being able to steer easily and straight in reverse means you are driving the boat from a foot away from the end instead of trying to see a bow that is 40 feet ahead of you
Thanks, do you happen to know what the diameter of your prop and the pitch setting? Any other characteristics of the 4100 that I should be concerned with? She seem to really sail well. What size is your foresail?
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