Running an I/O on "earmuffs"
 

I have hooked a hose up to my Volvo Penta to start the motor in my driveway to check things out and don't have a problem doing so but my question is, is it okay to put the motor in gear while on the muffs?
i have been showing the boat to prospective buyers and not starting it but would demonstrate how good the motor runs by using the hose and muffs...just wondering if it's okay to put it in gear to mak the prop turn (carefully, of course)

Not a problem at all, except for the safety aspect. Be sure there's nothing to foul the prop or better yet, remove it first.

Should be fine, just keep it at idle speed and make sure no one (or the hoses) are near the prop.

Echo'ing the above

Yes, you can put it in gear. VERY LOW to show that the prop will in fact spin but you can not rev the motor "muffs" will not be able to suck in enough water.

I was surprised to see people say yes. I have read in multiple factory manuals that you should never put the motor in gear when it's out of the water, even if it's connect to muffs. There is absolutely no resistance on the prop, so it's going to spin very fast, and when you take it in/out of gear, it can do damage to the prop hub, as well as other parts. If you really need to spin the prop, back it down a ramp, or lower the drive in a tub of water.

In this thread, when it is mentioned to put it "in gear" that only refers to engaging the clutch. The prop will barley turn, if at all. It is not going to "spin very fast, and when you take it in/out of gear, it can do damage to the prop hub, as well as other parts." It was never mentioned to go "full throttle".

I would guess that the factory manuals you are reading that in are stating that for liability reasons only.

Putting it In Gear ..On the Muffs is NO PROBLEM. Just don't REV It Up...Forward..Reverse...NO Problem. :) NB

I think "Outdoorsman " is WAY OFF Track..AGAIN. HE..OR SHE.. has NO Clue. Outdoorsman has NO Clew what a Clutch is. NB :eek:

The troll above failed to read and comprehend my post YET AGAIN. The bold that it quoted was a previous quote from the OP, it even has quotation marks around it.

What do you think happens when you put the drive in gear at idle? You move forward at basically headway speed depending on the conditions...so yes, the props are moving at a steady pace.

Running the drive out of the water on muffs will not harm it at idle speeds.

If you put it in gear, with the prop out of water, there will be no resistance, and it will move very fast. I follow the factory manuals, and it keeps me out of trouble. And I was simply responding to the OP. If you want to risk the damage, go for it. For me, I'd take the time and put the drive in some water, just to be safe.

The speed of the propeller shaft varies directly with that of the power head.

800 rpm on the power head in the water will give you the same prop speed as 800 rpm on the muffs.

The only thing that I can think of that could cause damage is if you shift at too high an rpm. I the water, a sudden reduction in throttle will reduce rpms more quickly due to the water resistance on the prop. Out of the water, the power head tends to coast a bit during sudden decelleration. Shifting then, while the rpms are still high, might hurt the gears in the lower unit.

Hey Outdoorsman...I guess we disagree. I'm not offended by your Troll reference. Maybe I can be the BEST Troll on this forum... :D :D I Always aspire to be the Best. Best to you my friend. :):) NB

Physics
 

There is a mix of good/bad info here. There is no difference putting the motor in gear at idle in or out of the water. The prop shaft will actually spin the prop with less initial resistance than if the prop was in the water. The problem is if you go from forward to reverse without letting the prop stop spinning in neutral first. That could cause the prop hub to spin within the prop, damaging the prop.

I mean if you think about it - will it wreck the transmission in a car if you jack up the drive wheels off the ground and put the car in gear? Of course not, unless your name is Ferris Bueller. :rolleye2:

When I was towing and working on my boat myself (260 Mercruiser) I would always test forward / reverse while running on the muffs to be sure the boat would start and shift properly at launch time.

It's all been mentioned above: make sure prop is clear, don't run above idle speed and let the prop come to a complete stop before shifting into the opposite direction. Didn't want a surprise on the ramp, never had any issues.