Prop is turning in neutral

Feb 10, 2017
305
Hunter 41 Progreso
I have to calibrate something in my gear box ? my h41 with a yanmar 56 hp and prop with shaft is turning in neutral.
It is normal ?
 
Jul 12, 2011
1,165
Leopard 40 Jupiter, Florida
If it's rotating slowly, could it be sympathetic vibration of the shaft due to the engine running? Is it spinning around like it's in gear? That's problems with your transmission that I've never heard of.
 
Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
You did not say - but one assumes your motor is a Yanmar 4JH3E. If so you should have a Kanzaki marine gear. There is a tag on the gear case which will tell you the model.

Adjustments are possible however it is very rare to find that adjustments have gone wrong but check that the cable mount and its connections are solid and make sure the cable moves the shift arm to the neutral position.

So first - change the transmission oil. Inspect the oil you remove to rule out any possible water in the oil. Refill the gearcase with the type oil listed on the tag. It is very common to find a prior person wrongly used ATF when SAE 30 is the correct oil. In any case frequent changes keep the oil clean and that is important because Kanzaki transmission oil capacity is relatively small. By the way - to avoid damage keep the transmission in neutral when sailing.

Charles
 
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Feb 10, 2017
305
Hunter 41 Progreso
thanks to all the replay, i was not using the right point for the neutral and the cables have moved, all ok right now. very hard to find monograde 30 oil.
 
Jun 11, 2011
1,243
Hunter 41 Lewes
Rotella T 30W for the trans and 15-40W for the engine. Depending on the year the engine could be a 4JH4E also.
 
May 24, 2004
7,129
CC 30 South Florida
It is recommended by Yanmar that the transmission be set on neutral when under sail, and yes the shaft will spin as the propeller turns in the water. I use synthetic oil for the transmission as it is in an enclosed space practically free of contamination. Synthetic oil has greater resistance to thermal and chemical breakdown. I replaced the oil 5 years ago and do not expect to have to replace it again. I do monitor the oil level and viscosity and have encountered no leaks. The same cannot be said about the engine as the combustion process contaminates and degrades the oil and needs periodic replacement.
 
Jun 1, 2009
1,737
Hunter 49 toronto
It is recommended by Yanmar that the transmission be set on neutral when under sail, and yes the shaft will spin as the propeller turns in the water. I use synthetic oil for the transmission as it is in an enclosed space practically free of contamination. Synthetic oil has greater resistance to thermal and chemical breakdown. I replaced the oil 5 years ago and do not expect to have to replace it again. I do monitor the oil level and viscosity and have encountered no leaks. The same cannot be said about the engine as the combustion process contaminates and degrades the oil and needs periodic replacement.
Ok, my TWO CENTS
Letting the engine spin in neutral while sailing is not a great thing to be doing to the transmission. But, it is better than leaving the engine in gear which puts huge forces in the shaft, coupling, and components
Having a fixed prop on a boat 40ft & up is a mismatch.
On that size boat, you are more prone to docking calamities owing to prop walk. Also, even if you have the prop free wheeling, there is a significant amount of drag.
Once you are investing in a larger boat, a feathering prop such as maxprop or variprop is not a luxury. It’s just standard gear.
You wil reverse dead straight,, have much better control when coming into a dock, and there is no issue with shaft spinning.
Yes, this costs money.
But, it is worth every penny
 
Dec 19, 2006
5,809
Hunter 36 Punta Gorda
I have a Flex O Fold prop and need to put it in Reverse to have prop to fold and add changed to
Flex O Fold in 2008 and been putting in Reverse and everything works great.
When I had 2001 H-290 with 2GM Yanmar and put in reverse when sailing also.
Nick
 

RoyS

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Jun 3, 2012
1,739
Hunter 33 Steamboat Wharf, Hull, MA
I have a Max Prop on my 33' and still experience serious prop walk in reverse.
 
May 24, 2004
7,129
CC 30 South Florida
Yanmar a few years back changed its tune to recommend the transmission be set on neutral. The transmissions are constant mesh and well lubricated by the spinning forces. These transmissions are quite hardy and will take thousands of hours under sail before any ill effects are noticed.
 
Jan 8, 2015
360
MacGregor 26S, Goman Express 30 Kerr Reservoir
Yanmar a few years back changed its tune to recommend the transmission be set on neutral. The transmissions are constant mesh and well lubricated by the spinning forces. These transmissions are quite hardy and will take thousands of hours under sail before any ill effects are noticed.
Yes but what about that anoying noise from the shaft spinning when all else is quiet except the peacful slapping of waves against the hull?
 
Jun 1, 2009
1,737
Hunter 49 toronto
I don’t see how that is possible.
The reason that you have prop walk is because standard fixed propellers have a pitch to them.
Just to review what “pitch” is, it is the theoretical amount of movement generated by a spinning propeller as it pulls itself through the water. (Think of an auger)
Now, the weight of the boat, and all other factors subtract from the theoretical ideal pitch calculation
A fixed propeller has sculpted (curved) blades, which is what grabs the water and displaces it.
There are 2 displacement vectors: one is the water being pushed back (or forwards) and the other pushing the water to the side. This side force is a function of the blade shape being curved.
You don’t notice the side force as much going in forward for 2 reasons:
Fixed propellers are optimized for the forward direction. Secondly, they are pushing water back past the rudder, which imparts additional steering thrust.
When going in reverse, 2 things happen:
You are using the less favoured (or less efficient) pitch characteristics of the propeller which has a higher ratio of side thrust to reverse moment.
Also, you aren’t using the laminar flow over your rudder nearly as efficiently, because the boat is moving slower.
The advantage of the max props is that the blades are flat, and the pitch is derived by angling the blades to the desired pitch, which is determined when the prop is installed
On a max prop, the pitch setup is programmed by messing around with how the internal gear pieces are inststalled. On a vari prop it’s much simpler... just some set screw end stop adjustments.
So,,,,
What I’m saying is that the max prop has very minimal side thrust because the blades are flat. On my hunter 40.5, I was astonished the first time I backed out of my slip. Dead straight.
So,,, I honestly can’t imagine where your prop walk is coming from.
 
Jan 8, 2015
360
MacGregor 26S, Goman Express 30 Kerr Reservoir
I don’t see how that is possible.
So,,, I honestly can’t imagine where your prop walk is coming from.

Prop walk is caused by the angle of the propeller shaft to the water surface; if there is no angle, then there is no prop
walk. For an increase in either the diameter or pitch of the propeller the effect is increased.
 
Jun 1, 2009
1,737
Hunter 49 toronto
A agree completely.
On a large number of C&C yachts they angled the shafts.
I have never seen a hunter with an angled shaft. Please correct me I’m wrong.
 
Feb 2, 2006
464
Hunter Legend 35 Kingston
A agree completely.
On a large number of C&C yachts they angled the shafts.
I have never seen a hunter with an angled shaft. Please correct me I’m wrong.
Are you two talking two different angles? I have seen a few C&Cs with the prop shaft angled laterally ( and also angled vertically). But I've rarely any production boats without an angle in the vertical direction (Saildrives generally have no vertical angle). I don't really know but thought the laterally angled prop shafts helped get the shaft past the rudder if you had to remove it.

Cowpokee is referring to vertical or angle to the waterline. A portion (I always thought the primary portion) of prop walk is due the basic physics of actual angle of the the blades to the direction of motion on each side (laterally) of the prop shaft. If the shaft is angled, then the prop does NOT push (or pull) equally on each side of the shaft no matter whether you have a flexofold, maxprop, or any fancy or fixed prop. if your shaft is angled down, relative to the waterline, then you will have unequal forces, and presumably proportional to the amount of angle.

Chris