Volvo Penta Gear Oil

[JamesG161]

My MD22L has a reverse gear which supposedly requires just VP's own brand oil at $50 a quart!
I check my gear oil every 3 months and for the first time found it to be "Burnt" but still had lubricity.
@Rich Stidger has the same engine and we have been chatting in a private message about the required GL5 synthetic oil required by the manual, 5/8 th of a quart.
SAE75W-90 Full Synthetic.

I proposed a more Heavy Duty oil for the higher temperature waters here on the Gulf.
Rich convinced me, no hard to do because of his top notch reputation here on SBO, to go with the manual instead of this...
http://www.truevalue.com/catalog/product.jsp?productId=41238
SAE85W-140 Full Synthetic

Any other thoughts on why not Heavy Duty?

I had mine changed in Punta Gorda 2.5 years ago. I have the remaining VP oil that looks light yellow and less lubricity than Mazola corn oil. I wonder if I been using a VP outdrive gear oil and not their inboard drive gear oil.


This has just happened with no particular strain on the gear.
However, recent max hull speeds sailing had my prop spinning very rapidly, but gear was supposedly in the Neutral.

What this might do is rotate the unengaged gears without the normal sea water oil cooler running.

Any thought on the change in oil condition?
Jim...

 

[Rich Stidger]

I believe that Volvo recommends putting the transmission in gear to stop the prop while under sail. Transmission rotation and overheating was the driving factor. I would have to look in the manuals for that recommendation. Since I have a feathering prop, I always shift to reverse when sailing so the prop feathers. Of course this stops the rotation as well. Sorry I didn't think of this as a cause for your burnt oil condition before now.

On this board I have seen that there are varying opinions on this. Apparently some manufactures don't specifically recommend the "in gear" setting while sailing and others claim that you can go faster if the prop spins. I think you need to get the right answer for your MS2A transmission.

 

[kloudie1]

I don't think that stuff is unavailable.. A jobber would have something like this:
http://www.mscdirect.com/product/details/60002755

 

[JamesG161]

I would have to look in the manuals for that recommendation

Found it!
When under sail, the control lever should be in the neutral position if the propeller is a fixed propeller. If the propeller is a folding propeller, the control lever should be in the reverse position.

Fact: It takes energy to spin a propeller.

Without the engine running, just where does that energy come from?

http://forums.sailboatowners.com/index.php?threads/prop-spinning-undersail.179024/#post-1294229

This has perhaps added new meaning to the post above.
Jim...

 

[JamesG161]

A jobber would have something like this

Thanks for the link. Us mad scientists like this viscosity info best...

120 cSt Viscosity at 40 Degrees C, 15.9 cSt Viscosity at 100 Degrees C
from that link.

CST is not central standard time.
It is centiStokes a true viscosity unit. Room temperature Water = 1 cSt . The bigger the number the more lubricity, but the key is the temperature performance.
I will break out my Laser Temperature gun next time the prop is spinning like crazy.

But the higher the Weight oil, the better the temperature performance.
Jim...

 

[Davidasailor26]

Found it!
When under sail, the control lever should be in the neutral position if the propeller is a fixed propeller. If the propeller is a folding propeller, the control lever should be in the reverse position.

Fact: It takes energy to spin a propeller.

Without the engine running, just where does that energy come from?

http://forums.sailboatowners.com/index.php?threads/prop-spinning-undersail.179024/#post-1294229

This has perhaps added new meaning to the post above.
Jim...

There are a couple of things going on here. First is what gear is best for the transmission itself. There are plenty of threads on that depending on transmission type. The second part is whether a spinning or locked prop is less drag. The energy it takes to spin the propeller does not correctly answer that question. Think of it this way - it also takes energy to spin the wheels of a car, but keeping the brakes locked does not keep a car moving faster than coasting in neutral. The energy it takes to spin the prop is just less energy lost to friction and heat. Check the archives for some pretty definitive experiments from Maine Sail showing that spinning is less drag than fixed.

 

[JamesG161]

that spinning is less drag than fixed.

Drag is what pushes your boat forward when in gear. My 50 Hp Volvo Penta uses about 30 Hp to overcome my boats's Drag.

A folding prop reduces the Drag.

Drag is what is adding energy or heat to my gear box.

I wonder which would add more Energy to the gear box, fast or slow spin?

I wonder if I didn't let the propellor spin in neutral, and if I was "racing", maybe align my "non spinning" 2 bladed prop, parallel with my keel, less drag, more SOG?
Hmmmmm....

Then Energy from the prop Drag would not be transferred to the Gear Box oil.
______________
@Rich Stidger this looks like the spec'd Gear Oil. What do you think?
http://www.autozone.com/greases-and...synthetic-gear-oil-sae-75w-90-1-qt-/1437_0_0/
More in line with good price.
Jim...

 

[Rich Stidger]

this looks like the spec'd Gear Oil. What do you think?
http://www.autozone.com/greases-and...synthetic-gear-oil-sae-75w-90-1-qt-/1437_0_0/
More in line with good price.
Jim...

I use this particular oil or Valvoline, or any other name-brand oil with the same characteristics.

 

[Davidasailor26]

Drag is what pushes your boat forward when in gear. My 50 Hp Volvo Penta uses about 30 Hp to overcome my boats's Drag.

A folding prop reduces the Drag.

Drag is what is adding energy or heat to my gear box.

I wonder which would add more Energy to the gear box, fast or slow spin?

I wonder if I didn't let the propellor spin in neutral, and if I was "racing", maybe align my "non spinning" 2 bladed prop, parallel with my keel, less drag, more SOG?
Hmmmmm....

Then Energy from the prop Drag would not be transferred to the Gear Box oil.
______________
@Rich Stidger this looks like the spec'd Gear Oil. What do you think?
http://www.autozone.com/greases-and...synthetic-gear-oil-sae-75w-90-1-qt-/1437_0_0/
More in line with good price.
Jim...

I would say that lift pulls the boat forward, not drag. You're using 30HP of lift to overcome the drag of the hull. For that reason, the spinning prop is still less drag than a fixed one.

A spinning prop will transfer more energy to your gear box, but a locked prop will transfer more energy to the water through friction. Just like locked car tires transfer more energy to the road through friction than coasting.

A good comparison of a fixed prop in line with the keel/rudder to a spinning one is something I haven't seen done. That would be interesting, and would likely depend on the geometry of the hull.

 

[JamesG161]

I would say that lift pulls the boat forward, not drag

As you wish to call it.

But it is differential pressure that "pumps" water by the prop's spin. Jet motors pump water.

No doubt Lift plays a part in propeller efficiency to pump water by frictional Drag of water over the blades surface as it pumps water.
________
I am going to test the temperature of the gear box , spinning and not spinning and report back to this thread.
Jim...

PS: Frictionless blades won't pump or propel your boat.

 

[woodster]

reading this thread i had a thought as to maybe the gearbox people could put a parking gear in there when they build them ....that would squash the dilemma for one and for all...i know they make shaft breaks ....why not parking gears......

 

[JamesG161]

why not parking gears......

I think that is the effect of using reverse for the folding prop, too "fold" the prop. I am going to try your "parking break" idea, but parked with the blades aligned with the keel for minimum Drag or force applied to the gear box.
In thinking this out (rare for me), I could align the prop and put the transmission in reverse.
It would be no shaft forces exceeding the 50 hp design

Kudos to Woodster, Rich Stidger and my son-in-law who owned a boat repair business for their insight.
Jim...

 

[Captn Scotty]

I know that a helicopter whose engine dies in flight can coast to the ground if the blades are still spinning, but one with locked blades drops like a rock. Wouldn't the same principles of lift and drag apply to a vessel?

 

[JohnCTV21]

An "auto rotation" by a helicopter is a product of negative blade pitch and forward movement.
The spinning of the rotor disk combined with movement of air over the disk creates lift.
The air passing through the negative pitch blades is what keeps them spinning.

 

[JamesG161]

Wouldn't the same principles of lift and drag apply to a vessel?

Yes.
Differential pressure provides the thrust as air drags over blades.
Jim...

PS: Helicopter's blades change pitch though.

 

[Captn Scotty]

Okay, now I get it , thanks. It just seemed that the power to spin the blades and shaft would be significantly more than fixed

 

[Davidasailor26]

Okay, now I get it , thanks. It just seemed that the power to spin the blades and shaft would be significantly more than fixed

Just to be clear, the helecopter analogy doesn't mean that the boat is slower with the prop freewheeling. The helecopter blades generate upward lift when they're spinning, but the prop blades generate forward lift when they're spinning. It's not enough lift to overcome the drag of the blades themselves, but more than if they weren't spinning at all. Net force is still aft, but not as strongly aft with the freewheel.

 

[Johann]

Really we are dealing with two separate equations for either form drag (fixed prop/rotor) or rotational energy (spinning prop/rotor). The question is which is greater, and the answer is, well it depends. Form drag is based on, among other things, the area of the body presented to the fluid, the density of the fluid, and the velocity squared. The rotational energy is based on the rotational inertia and the angular velocity squared. In the helicopters case, the blades have a relatively small area, low fluid density, and insufficient velocity to counteract gravity. However, the blades have a large rotational inertia, and angular velocity if spinning. Thus the spinning helicopter blades will provide more drag.

The boat prop, on the other hand, has a small rotational inertia, and it not spinning very fast. It also has a relatively large area and is travelling through a dense fluid. So at the boat speeds we are talking about, the form drag (fixed prop) is higher. I'm not sure, though, that at some velocity through the water, the angular energy may surpass the form drag... But clearly not at 7 knots.

I can tell you regarding prop driven aircraft, the last thing you want is an unpowered spinning prop. Frozen.. fine. Feathered... even better. But unpowered and spinning you might as well have a drogue chute deployed.

 

[JamesG161]

drag is based on, among other things, the area of the body presented to the fluid, the density of the fluid, and the velocity squared.

You just did the simplified Force of Drag Equation found here.
https://en.wikipedia.org/wiki/Drag_coefficient
Add viscosity/temperature effects of the fluid (normally near a constant in Salt water) and propeller surface smoothness (normally super smooth without barnacles) and we have it. Oh no I forgot possible cavitation (so make the propeller tips a knife edge).
______
I started the thread, wondering why my Gear Oil had quickly gone dark or "burnt" looking.
Then I pondered how much gear box Frictional heat was being added by my propeller. when spinning rapidly at near hull speeds.

I have referred to Drag buy common fluid dynamic terms.
Not meaning an boring date, inhaling a tobacco product, or the feeling I am getting about this thread switching to Helicopters.
But IMHO any discussion of any thing in a thread is OK. You have control to read or not read any updates.
___________
I am now perfectly clear that the propeller's spinning energy driven by my boat's forward motion...

Will ADD more heat to my gear box oil than a non spinning propeller.

This is a separate thought from Speed over Ground reduction.
Jim...

PS: I wonder why we don't use a big propeller to drive a space craft to Mars? You wonder if Drag is not much when their is no fluid density?