rpm max in reverse ...thoughts?

[bob johnson]

soooo i am having rpm issues...havent quite nailed it down Ive been running a 15 X15 prop...its in good condition, and so while there were things to check out on the motor, id thought Id try a different prop anyway. I had a 15 X17 stainless steel prop.... i figured it might be a wash, it was stainelss the other one is aluminum. launch the boat at the ramp , push off and put it in reverse...the boat heads back into the ramp!...waaaa... try it again...drives me back into the ramp.... i put it in forward and sure enough Im backing up...... the prop is a counter rotating prop! I never knew that spare motor was a counter rotating motor...( i bought it for the powerhead....) sooo im in the water and dont want to load back up...so i throw the shifter in reverse and away i go...FORWARD...... so Im thinking....am I going to damage anything?....im guessing the only thing that previously preventing from rev-ing the boat in reverse was the gallon and gallons of water that would try to climb into the back of the boat! does the clutch dog or the reverse gear take a SET? in anyway.... maybe it was my imagination but after running up to 3000 rpm seemingly ok eventually I thought it felt a little funny...plus it SEEMED like the steering was harder.....anyone ever do this before?..... eventually i pulled over to the bank and put my spare prop on.... wondering is there a bad side to running a regular motor at high rpms in reverse?

 

[racerone]

What motor is this again ?----Model # should clear this up.

 

[dingbat]

Running bevel gears backwards from their normal rotation detrimental to their existence.

Change the lower unit or prop or you’ll be looking for a new LU

 

[racerone]

????-----I would think the gears on a normal rotation motor and counter rotating prop motor both turn the same way !!!

 

[Rustywrench]

Gears are turning the same way, but you are running off the back gear instead of the front gear in the gearcase. The gearcase was not designed for this. Will not last with that load on it. Hope you did not damage it already. I would check/change your gear lube.

 

[bob johnson]

ok so the the lower unit is from a 1997 175 hp Johnson faststrike 20" shaft..... i dont think it matters but the power head is a 1999 Johnson 150 ocean runner. it seems to me the if you are pushing a gear... you are pushing the normal mating face in both forward and reverse..... Im thinking the only thing not normal is that the prop is pushing me the opposite way....but Im not sure....so i asked here.....

 

[racerone]

At this time we do not know if you have a reverse rotation lower unit or simply the wrong prop.----Pictures and more pictures.

 

[bob johnson]

At this time we do not know if you have a reverse rotation lower unit or simply the wrong prop.----Pictures and more pictures.

just the wrong prop..... i had a running motor but was not up to the rpms that it should be at...so along with engine checks, i thought id try a SS prop I had sitting on an extra midsection(so probably counter rotating ) ,to see if i could get more rpms....the prop I had been using was aluminum...... i decarbed this weekend and then i checked compression all 90-100.... figured id try a different prop to see if i could get the motor over 4100 rpms...... so anyway.......this question was about the effects of running the wrong rotation Prop on a motor..... and shifting into reverse to go forward.....what do you think?

 

[dingbat]

????-----I would think the gears on a normal rotation motor and counter rotating prop motor both turn the same way !!!

Motor doesn't run backwards....how do you make a shaft turn in the opposite direction without using left and right hand gear sets?

Normal rotation and CR use different gear sets. Clutch dog isn't going to like it either

 

[Lightwin 3]

Motor doesn't run backwards....how do you make a shaft turn in the opposite direction without using left and right hand gear sets?

Normal rotation and CR use different gear sets. Clutch dog isn't going to like it either

True-engine does NOT run backwards. Counter rotation takes place in gear set. Forward gear is cut exactly opposite of a standard rotation engine.

 

[bob johnson]

True-engine does NOT run backwards. Counter rotation takes place in gear set. Forward gear is cut exactly opposite of a standard rotation engine.

now it is entirely true I might be talking out my ..you know what......but.....if we were trying to turn the reverse gear the wrong way with the correct prop...we would be pushing on the gears in the wrong direction... ..but my motor is pushing the reverse gear the way it is supposed to be pushed!!!! the way it was designed..... the motor is all working the way it should it just doesnt know there is a backwards prop on the end!....so that funky prop pushes the boat the opposite direct...but it seems to me.... the gears in the lower unit are meshing as if the boat was going in reverse......... the GEARS DONT KNOW THE BOAT IS GOING THE WRONG DIRECTION.........thats how im visualizing this......... and i acknowledge..i could be missing something... when in doubt..just ask..... the world is full of people smarter than me! ha ha

 

[bob johnson]

the more i think about the more im convinced that the only way to ruin the gears is for the motor to spin the opposite direction.......if the pinion gear engages the reverse gear.... the prop turns one direction...if it engages the forward gear, the prop turns the opposite direction.........the motors drives shaft rotation is constant........ i guess one of my question kinda was...is the reverse gear designed to spin at high rpm...like the forward gear........im believeing that the answer should be yes......

 

[dingbat]

the more i think about the more im convinced that the only way to ruin the gears is for the motor to spin the opposite direction......

A right-hand spiral bevel pinion gear rotating clockwise will tend to move toward the cone center, while a left-hand spiral bevel pinion tends to move away from the cone center because of the oblique direction of the curved teeth. If end play exists in the pinion shaft, the movement of a right-hand spiral bevel pinion driving in the clockwise direction will take up the backlash under heavy load and the teeth of the crown and pinion may wedge together.

A left-hand spiral bevel pinion under similar conditions will back away from the crown; therefore, this introduces additional backlash between the teeth.

It is recommended that when the ratio, pressure angle, and spiral angle are specified, the hand of the spiral should be selected to provide an axial thrust that tends to move the pinion out of mesh. In many applications, the mounting conditions will typically dictate the hand of spiral to be used.

 

[Lightwin 3]

Regardless of the gears, having boat controls that work exactly backwards is a disaster looking for a place to happen.

It's counter (pun intended) intuitive to what you have always known.

 

[racerone]

Dingbat----Time to look up information on counter rotation gearcases.----It is the bearing set up on the reverse gear and propshaft that makes the difference.-----It is all really simple when you understand this stuff !!

 

[F_R]

Nuts to all the gear talk. When you put a "normal" gearcase, in forward gear, the prop shaft and forward gear push forward against some hefty thrust bearings in the nose of the case. Put it in reverse and the prop shaft and reverse gear pull outward against some cheaper and weaker thrust bearings against the bearing housing. So, running in reverse constantly and under power means the reverse gear is running against the weaker bearings under a heavier load than they were designed for. So, you might argue the backwards prop is pushing the prop shaft forward to make the boat go forward, but that's only part of the story. The reverse gear is still running against those weak bearings.

Now that I've said all that, lemme sit and ponder it awhile before somebody proves me wrong.

 

[racerone]

On a normal lower unit the gear at the front is forward gear and just needs a bushing as it normally rotates with the propshaft.---No relative movement !-----But on some counter rotators that front gear now uses a needle bearing because the gear rotates at 2500 rpm one way and the shaft rotates at 2500 rpm the opposite way.----So it is all about arrangement of bearings in these counter rotators .

 

[Fed]

Aren't the remote controllers throttle limited in the reverse direction?

 

[Faztbullet]

Motor doesn't run backwards..​

A 1987 200hp Johnson counter rotating does!!!!

 

[Lightwin 3]

Well, who knew?

Anyway, as said before, using controls in reverse (backwards) does not promote safety.

GET A NEW PROP.