"Windmilling" or "What Every Trailerboater Should Know"

  ContinuousWave
  Whaler
  Moderated Discussion Areas
  ContinuousWave: The Whaler GAM or General Area
  "Windmilling" or "What Every Trailerboater Should Know"

search | FAQ | profile | register | author help

Author Topic:   "Windmilling" or "What Every Trailerboater Should Know"

Steve Leone posted 04-30-2003 01:08 AM ET (US)
"Windmilling" is a term used by Marine Engine Franchisers (Outboards and I/O`s) to describe what takes place at the prop when you are flying down the byways and highways with a boat in tow. It is in most owners manuals but needless to say very overlooked. It causes damage to the reverse gear in the lower unit in some models. It is NOT covered under warranty and is a great cause of distress and dismay with franchise owners. Apparently if you drive your boat around with the motor in neutral the propeller will free spin by the wind created and will do some nasty damage. Units must be in FOWARD gear to avoid this delema. Especially Mercury outboards. Oh, and you franchise owners, make sure you keep the doors closed or at least put all your display models in foward, peticularly on those windy days.......Steve ps why did`nt they install that $.05 cent washer in front of the reverse gear?
triblet posted 04-30-2003 11:45 AM ET (US)
I've read my Evinrude owner's manual cover to
cover a couple of times, and didn't see any
reference to this. Anybody seen it in an OMC
owner's manual?
Chuck
hauptjm posted 04-30-2003 11:55 AM ET (US)
Never heard of it!
where2 posted 04-30-2003 12:12 PM ET (US)
Oh, is this to say that the same damage would be covered if it happened while my boat was on anchor for the same 8 hour afternoon in a current capable of "windmilling" the prop?
The engineer in me REALLY wants to know what thrust washer was missing to allow the "windmilling" to mill the reverse gear. There ought to be a tolerance for end play that leaves the gears far enough apart that they don't mill themselves... If not, then maybe they should take a cue from their automotive gearbox brothers and slip a flimsy synchro in there to be machined, rather than the expensive gear...
brisboats posted 04-30-2003 05:03 PM ET (US)
Huh?, this is news to me. But I am messing around with some mercury outboards in the boat yard. A lot of the non power trim motors must be shifted into forward to tilt. You hopefully drive with the engine tilted and therefore it would be in forward. I have been towing lots of boats without shifting the gearbox and have not experienced this but perhaps I have just been lucky to escape the windmilling devil.
Brian
Steve Leone posted 04-30-2003 09:12 PM ET (US)
Triblet, I believe later O.M.C are equiped with said washer. As for ratcheting in the water caused by current apparently that is ok because it would be in FOWARD in order to ratchet I surmise. "windmilling" in the water apparently is different (thats what the rep said). I guess there are no currents that exceed 55 MPH or if there was you should not have your boat anchored in it. I will scan the Mercury Manual and post it when my scanner returns from the dead. Steve
triblet posted 04-30-2003 10:53 PM ET (US)
I've seen the prop spin pretty good when
anchored in a 1 knot current and Everrude
was in neutral. In fact, it spun faster than
I've ever seen a prop spin on the trailer.

Chuck
where2 posted 05-02-2003 12:45 PM ET (US)
"Windmilling in the water is different, (atleast that's what the rep said)" How is this different? It's the same force, applied in the same direction by a liquid rather than a gas (air). The limiting factor on the velocity that the prop windmills at is the force necessary to turn the forward and reverse gears in the gearcase oil inside the lower unit. The viscosity of the gearcase oil actually limits the minimum air velocity necessary to "windmill" the prop while traveling down the highway. Water being a liquid, tends to apply greater force at a lower velocity, thus Triblet's comment that "he'd seen the prop windmill at anchor at a higher rate than ever seen on the highway".
triblet posted 05-02-2003 01:25 PM ET (US)
So why isn't windmilling a problem in the water?

Chuck
elaelap posted 05-02-2003 02:09 PM ET (US)
Nothing about this in the Yamaha 50 hp High Thrust owner's manual. Bungie cord time on the trailer for us paranoids, or just remembering to engage the gears...?
Tony
ShrimpBurrito posted 05-02-2003 02:47 PM ET (US)
I didn't see anything about it in my Johnson manual for my 1987 40 HP. I'm definitely curious.....
diveorfish posted 05-02-2003 05:55 PM ET (US)
What�s the verdict gentleman? Forget about it, or put it in gear? I�m just as paranoid as elaelap.
Salmon Tub posted 05-02-2003 07:56 PM ET (US)
I have been trying to mentally picture a standard lower gear case for a few days now, and I still don't see what could happen. Granted, the worst I could picture is that if you were travelling at 55mph, and your prop was turning fast enough so that there was no slipage, then the prop would be turning faster than it would ever have on most boats when at WOT on the water, and perhaps, this creates some heat that does not disipate as fast in the air as it would in the water.
The other clue here is Mercury. Maybe in Merc. lower units, the prop shaft moves front and back and is designed to do so, utilizing thrust created by the prop in some way to keep the gears engaged. As far as I recall, on my Nissan, the shaft is solid with no play, in any axis.
Jay A posted 05-02-2003 11:08 PM ET (US)
Steve: Slow down! ..."Windmilling" Now that's funny! But if your serious...Don't worry 'bout nuttin!
spotsnspecks posted 05-02-2003 11:22 PM ET (US)
I have been told to keep my throttle engaged while trailering for years and have followed the advice of my peers/outboard mentors. Unfortunately, I can't find anything on windmilling in my owners manual either. I recall being told, windmilling could cause a hub to spin or cause damage to the prop shaft.
Matthew posted 05-03-2003 12:22 AM ET (US)

The owners manual on my 2002 90 hp Mercury 2 stroke say to: "Shift the outboard to forward gear. This prevents the propeller from spinning freely." and had always been taught that this was the way to go with my former engine 1981 OMC 70 as well.
Matt
Steve Leone posted 05-03-2003 12:39 AM ET (US)
JayA, just about as serious as a $2000.00 bill. Thats what the customer had to fork over to get back in the water. Nearly a brand new Merc. still under warranty. Still laughing? Steve
Jay A posted 05-03-2003 04:21 PM ET (US)
Yes! I've trailered my 13' Whaler with a 1975 40hp Merc all over New England. In all that time and miles,I've never had a problem. In fact the only thing I've changed on the engine are the sparkplugs. And it still has the original prop! There must of been more to it than that. Sounds like the dealer made up that explaination to get the cash in hand. The dealer making the repairs probably caused more damage than Merc was willing to compensate. It's a practice that some dis-honest car dealers use to cover shoody warranty work.
DillonBW posted 05-03-2003 04:36 PM ET (US)
I have a bright orange drawstring bag that goes over my lower end when trailering. Keeps it from windmilling, road dirt etc AND gives that guy behind something to SEE when her is riding my tail!
Happy Whaler'in!
ducktwin posted 05-03-2003 07:46 PM ET (US)
I always put them in gear.
How would you know if your prop. was spinning if someone didn't tell you? That is how I found out, I had a freind following me once and he found it, "curious".
I believe a lot has to do with the way the wind flows around a trailered boat. Some do and some do not. Why risk it?
Steve Leone posted 05-03-2003 11:51 PM ET (US)
JayA, Actually the dealer is one of the most reputable dealers in California. I find it odd that someone who knows nearly entirely nothing about outboard service is so quick to dis another person and thier reputation without any first hand experience with that person whatsoever. Your prejudices are unwarranted. My scanner is up now and I will post "verbatem" the contents of the manual on this subject. JayA, if ignorance is bliss then you are in seventh heaven.... Steve
Jay A posted 05-04-2003 03:29 AM ET (US)
Steve: All I'm posting is from what info you have provided. In my 38 years of owning boats and motors of all types,never have I heard a word of "windmilling" or any other definition of the effects you discribe.
Also,from your response,I can only conclude: It was you who's been had!
The best advice I can give you.(1) Have the dealer give you a written estimate of the costs BEFORE the work.(2) If you believe it's too expensive or it should be covered under warrenty, take it somewhere else for a second opinion.
elaelap posted 05-04-2003 08:44 PM ET (US)
Jay A,
I don't think you understand...Steve is a certified marine mechanic, outboard motor rebuilder, and dealer himself; I doubt he's worried about getting ripped off regarding outboard motors. I for one take any advice he generously contributes very seriously.
Simple enough to keep the damn thing in gear from now on while trailering...it's just one more thing to remember at 5:15 on a foggy, drizzly morning. I like DillonBW's idea about using a bright-colored drawstring bag...put it on the maybe list, Tony.
elaelap posted 05-04-2003 09:15 PM ET (US)
And speaking of remembering...I always tilt my motor back down after trailering when the boat's at home. Two weeks ago I made it half way down my driveway like that when a little anti-Alzheimers birdy whispered in my sleepy ear. Last week I set up my new downrigger and headed to the ocean to try it out...whoops, forgot the eight pound lead weight. Three days ago I made it at least a mile from my house when that same little bird suggested that it would enhance my fishing possibilities if I brought my rods and reels with me. And today, Bodega Bay blown out (at least for me), I headed for the Petaluma River for a little striper action, put my boat in at the marina ramp, then went and shot the stuff with the harbor master for fifteen minutes, all the while my boat's sucking up dirty, oily, brackish river water...forgot to put the plug in.
You know, if I weren't looking sixty years of age right in the eyeball this memory stuff wouldn't bother me. And now I've gotta remember to keep my motor in gear also...thanks a million, Steve.
Tony
GeneNJ posted 05-04-2003 09:47 PM ET (US)
This windmilling sounds alot like the problem of towing an auto transmission car. Most are now moved by flatbed nowadays to prevent drive problems.
Jay A posted 05-04-2003 11:18 PM ET (US)
elaelap: This thing gets more "fishy" as it goes on! A "certified" mechanic should know better. After church yesterday I bumped into an old friend and happened to mention "windmilling" to him. He started to laugh! He's been a marine mechanic with his dad's buisness since his H.S. days. He answered back: "Why? Will the rubberband break?" He also mentioned that if that was a potential problem he would have seen it by now and would have received advisories from the manufacturers. He also pointed out that manufacturers would surely point it out clearly in the owners manuals and have warning labels in areas such as the shift lever. And besides, It would more likely happen in water with a current. And if that produces a problem with the engine....time to get another one!
ShrimpBurrito posted 05-05-2003 12:20 AM ET (US)
For those of you who argue, "I've never done it for 30 years, and the engine is still in great shape", think about this: there are quite a few people around that drink like a fish and smoke like an Indian chief, but they're still around at 85 years. Then there are those who lead a similar lifestyle who kick the bucket at age 50. It's all about risk: if you want to increase your chances of living that long, eliminate as many detriments as possible.
I might suggest the same theory holds true for engine outboards.
HappyTime posted 05-05-2003 01:29 PM ET (US)
I am not sure I've heard 'windmilling' but
my mechanic at The Outboard Motor Shop told me to put my kicker in gear to prevent it form free spinning in reverse while using the main motor.
Tom2697 posted 05-05-2003 03:00 PM ET (US)
There are basically two ways to kill gearing. One is to run them without lubricant. Two is to have them partially engaged or to mesh improperly. The only way I can see damage occuring by this windmilling effect is if the gears are clashing as the prop turns (wind resistance is usually not enough to overcome metal to metal contact) or if the lubricant is not touching the gears. It seems to me that the lubrication issue might be logical. It seems that todays' outboards raise higher out of the water and are also more streamlined in the lower units. This COULD mean that the lower unit oil will settle where it no longer provides lubrication to the gearing. Since all props will spin as though they are in reverse while experiencing the windmilling effect, the reversre gears will mesh and wear. Depending on the design of the internal cavity of the lower unit, Mercury outboards could be more susceptible to this problem. A simple fix is to tie the props so they don't spin, put the motor CAREFULLY into forward gear so as not to bend the shifting rods, or, one could always lower their motor so the oil contacts the gears (assuming the skeg does not drag on the ground).
BTW - I am not a certified marine mechanic...but I did do a stint as an engineer for an industrial gear manufacturer.
David Jenkins posted 05-05-2003 10:52 PM ET (US)
This is somewaht off-topic, but is there a problem with tilting a power-tilt motor all the way forward while trailering it? While this may or may not reduce "windmilling," it balances the weight of the motor directly over the transom versus having all the weight pulling back on the transom. Do most of you use "transom savers?"
where2 posted 05-06-2003 12:39 PM ET (US)
Still looking forward to why this is not a problem in the water, but it is on the highway... In the meantime, here's more on the water scenarios to think about...
So, will I have the same problem if I am doing 50mph, and pull the gearshift into neutral?
How about if I have dual engines and one of them dies. Do I have to tilt the dead engine clear of the water, or can I just leave it in neutral?
(For GeneNJ) In reality, the gearbox in the lower unit looks nothing like an automatic transmission on a car. It's actually less complicated than a manual transmission in car. It looks like 3 gears submerged in oil with bearings and thrust washers around for good measure. I wish I had my OMC manual here so I could scan this simple device.
Due to Steve's comment in his original post that said "Why didn't they install that $.05 washer in front of the reverse gear", I suspect it all boils down to a design flaw in Mercury outboards that causes something similar to idling a car with a manual transmission, and pulling the gearshift toward a gear, without pushing in the clutch. However, since you don't have synchros in a lower unit, you directly grind the gears...
kglinz posted 05-06-2003 12:53 PM ET (US)
The reason you can't compare to a car automatic transmission is that the transmission is lubricated and cooled by oil pumped by the transmission oil pump, which is driven by the input shaft. Engine not running, no lube. Same reason you can't "push start" an automatic.
elaelap posted 05-06-2003 01:37 PM ET (US)
I've trailered my boat twice since this thread began, and remembered to put the motor in gear...so what's the problem? Seems a simple enough solution, even if Steve is wrong. Is there any downside?
Tony

Hop to:

Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.

Author	Topic: "Windmilling" or "What Every Trailerboater Should Know"
Steve Leone	posted 04-30-2003 01:08 AM ET (US) "Windmilling" is a term used by Marine Engine Franchisers (Outboards and I/O`s) to describe what takes place at the prop when you are flying down the byways and highways with a boat in tow. It is in most owners manuals but needless to say very overlooked. It causes damage to the reverse gear in the lower unit in some models. It is NOT covered under warranty and is a great cause of distress and dismay with franchise owners. Apparently if you drive your boat around with the motor in neutral the propeller will free spin by the wind created and will do some nasty damage. Units must be in FOWARD gear to avoid this delema. Especially Mercury outboards. Oh, and you franchise owners, make sure you keep the doors closed or at least put all your display models in foward, peticularly on those windy days.......Steve ps why did`nt they install that $.05 cent washer in front of the reverse gear?
triblet	posted 04-30-2003 11:45 AM ET (US) I've read my Evinrude owner's manual cover to cover a couple of times, and didn't see any reference to this. Anybody seen it in an OMC owner's manual? Chuck
hauptjm	posted 04-30-2003 11:55 AM ET (US) Never heard of it!
where2	posted 04-30-2003 12:12 PM ET (US) Oh, is this to say that the same damage would be covered if it happened while my boat was on anchor for the same 8 hour afternoon in a current capable of "windmilling" the prop? The engineer in me REALLY wants to know what thrust washer was missing to allow the "windmilling" to mill the reverse gear. There ought to be a tolerance for end play that leaves the gears far enough apart that they don't mill themselves... If not, then maybe they should take a cue from their automotive gearbox brothers and slip a flimsy synchro in there to be machined, rather than the expensive gear...
brisboats	posted 04-30-2003 05:03 PM ET (US) Huh?, this is news to me. But I am messing around with some mercury outboards in the boat yard. A lot of the non power trim motors must be shifted into forward to tilt. You hopefully drive with the engine tilted and therefore it would be in forward. I have been towing lots of boats without shifting the gearbox and have not experienced this but perhaps I have just been lucky to escape the windmilling devil. Brian
Steve Leone	posted 04-30-2003 09:12 PM ET (US) Triblet, I believe later O.M.C are equiped with said washer. As for ratcheting in the water caused by current apparently that is ok because it would be in FOWARD in order to ratchet I surmise. "windmilling" in the water apparently is different (thats what the rep said). I guess there are no currents that exceed 55 MPH or if there was you should not have your boat anchored in it. I will scan the Mercury Manual and post it when my scanner returns from the dead. Steve
triblet	posted 04-30-2003 10:53 PM ET (US) I've seen the prop spin pretty good when anchored in a 1 knot current and Everrude was in neutral. In fact, it spun faster than I've ever seen a prop spin on the trailer. Chuck
where2	posted 05-02-2003 12:45 PM ET (US) "Windmilling in the water is different, (atleast that's what the rep said)" How is this different? It's the same force, applied in the same direction by a liquid rather than a gas (air). The limiting factor on the velocity that the prop windmills at is the force necessary to turn the forward and reverse gears in the gearcase oil inside the lower unit. The viscosity of the gearcase oil actually limits the minimum air velocity necessary to "windmill" the prop while traveling down the highway. Water being a liquid, tends to apply greater force at a lower velocity, thus Triblet's comment that "he'd seen the prop windmill at anchor at a higher rate than ever seen on the highway".
triblet	posted 05-02-2003 01:25 PM ET (US) So why isn't windmilling a problem in the water? Chuck
elaelap	posted 05-02-2003 02:09 PM ET (US) Nothing about this in the Yamaha 50 hp High Thrust owner's manual. Bungie cord time on the trailer for us paranoids, or just remembering to engage the gears...? Tony
ShrimpBurrito	posted 05-02-2003 02:47 PM ET (US) I didn't see anything about it in my Johnson manual for my 1987 40 HP. I'm definitely curious.....
diveorfish	posted 05-02-2003 05:55 PM ET (US) What�s the verdict gentleman? Forget about it, or put it in gear? I�m just as paranoid as elaelap.
Salmon Tub	posted 05-02-2003 07:56 PM ET (US) I have been trying to mentally picture a standard lower gear case for a few days now, and I still don't see what could happen. Granted, the worst I could picture is that if you were travelling at 55mph, and your prop was turning fast enough so that there was no slipage, then the prop would be turning faster than it would ever have on most boats when at WOT on the water, and perhaps, this creates some heat that does not disipate as fast in the air as it would in the water. The other clue here is Mercury. Maybe in Merc. lower units, the prop shaft moves front and back and is designed to do so, utilizing thrust created by the prop in some way to keep the gears engaged. As far as I recall, on my Nissan, the shaft is solid with no play, in any axis.
Jay A	posted 05-02-2003 11:08 PM ET (US) Steve: Slow down! ..."Windmilling" Now that's funny! But if your serious...Don't worry 'bout nuttin!
spotsnspecks	posted 05-02-2003 11:22 PM ET (US) I have been told to keep my throttle engaged while trailering for years and have followed the advice of my peers/outboard mentors. Unfortunately, I can't find anything on windmilling in my owners manual either. I recall being told, windmilling could cause a hub to spin or cause damage to the prop shaft.
Matthew	posted 05-03-2003 12:22 AM ET (US) The owners manual on my 2002 90 hp Mercury 2 stroke say to: "Shift the outboard to forward gear. This prevents the propeller from spinning freely." and had always been taught that this was the way to go with my former engine 1981 OMC 70 as well. Matt
Steve Leone	posted 05-03-2003 12:39 AM ET (US) JayA, just about as serious as a $2000.00 bill. Thats what the customer had to fork over to get back in the water. Nearly a brand new Merc. still under warranty. Still laughing? Steve
Jay A	posted 05-03-2003 04:21 PM ET (US) Yes! I've trailered my 13' Whaler with a 1975 40hp Merc all over New England. In all that time and miles,I've never had a problem. In fact the only thing I've changed on the engine are the sparkplugs. And it still has the original prop! There must of been more to it than that. Sounds like the dealer made up that explaination to get the cash in hand. The dealer making the repairs probably caused more damage than Merc was willing to compensate. It's a practice that some dis-honest car dealers use to cover shoody warranty work.
DillonBW	posted 05-03-2003 04:36 PM ET (US) I have a bright orange drawstring bag that goes over my lower end when trailering. Keeps it from windmilling, road dirt etc AND gives that guy behind something to SEE when her is riding my tail! Happy Whaler'in!
ducktwin	posted 05-03-2003 07:46 PM ET (US) I always put them in gear. How would you know if your prop. was spinning if someone didn't tell you? That is how I found out, I had a freind following me once and he found it, "curious". I believe a lot has to do with the way the wind flows around a trailered boat. Some do and some do not. Why risk it?
Steve Leone	posted 05-03-2003 11:51 PM ET (US) JayA, Actually the dealer is one of the most reputable dealers in California. I find it odd that someone who knows nearly entirely nothing about outboard service is so quick to dis another person and thier reputation without any first hand experience with that person whatsoever. Your prejudices are unwarranted. My scanner is up now and I will post "verbatem" the contents of the manual on this subject. JayA, if ignorance is bliss then you are in seventh heaven.... Steve
Jay A	posted 05-04-2003 03:29 AM ET (US) Steve: All I'm posting is from what info you have provided. In my 38 years of owning boats and motors of all types,never have I heard a word of "windmilling" or any other definition of the effects you discribe. Also,from your response,I can only conclude: It was you who's been had! The best advice I can give you.(1) Have the dealer give you a written estimate of the costs BEFORE the work.(2) If you believe it's too expensive or it should be covered under warrenty, take it somewhere else for a second opinion.
elaelap	posted 05-04-2003 08:44 PM ET (US) Jay A, I don't think you understand...Steve is a certified marine mechanic, outboard motor rebuilder, and dealer himself; I doubt he's worried about getting ripped off regarding outboard motors. I for one take any advice he generously contributes very seriously. Simple enough to keep the damn thing in gear from now on while trailering...it's just one more thing to remember at 5:15 on a foggy, drizzly morning. I like DillonBW's idea about using a bright-colored drawstring bag...put it on the maybe list, Tony.
elaelap	posted 05-04-2003 09:15 PM ET (US) And speaking of remembering...I always tilt my motor back down after trailering when the boat's at home. Two weeks ago I made it half way down my driveway like that when a little anti-Alzheimers birdy whispered in my sleepy ear. Last week I set up my new downrigger and headed to the ocean to try it out...whoops, forgot the eight pound lead weight. Three days ago I made it at least a mile from my house when that same little bird suggested that it would enhance my fishing possibilities if I brought my rods and reels with me. And today, Bodega Bay blown out (at least for me), I headed for the Petaluma River for a little striper action, put my boat in at the marina ramp, then went and shot the stuff with the harbor master for fifteen minutes, all the while my boat's sucking up dirty, oily, brackish river water...forgot to put the plug in. You know, if I weren't looking sixty years of age right in the eyeball this memory stuff wouldn't bother me. And now I've gotta remember to keep my motor in gear also...thanks a million, Steve. Tony
GeneNJ	posted 05-04-2003 09:47 PM ET (US) This windmilling sounds alot like the problem of towing an auto transmission car. Most are now moved by flatbed nowadays to prevent drive problems.
Jay A	posted 05-04-2003 11:18 PM ET (US) elaelap: This thing gets more "fishy" as it goes on! A "certified" mechanic should know better. After church yesterday I bumped into an old friend and happened to mention "windmilling" to him. He started to laugh! He's been a marine mechanic with his dad's buisness since his H.S. days. He answered back: "Why? Will the rubberband break?" He also mentioned that if that was a potential problem he would have seen it by now and would have received advisories from the manufacturers. He also pointed out that manufacturers would surely point it out clearly in the owners manuals and have warning labels in areas such as the shift lever. And besides, It would more likely happen in water with a current. And if that produces a problem with the engine....time to get another one!
ShrimpBurrito	posted 05-05-2003 12:20 AM ET (US) For those of you who argue, "I've never done it for 30 years, and the engine is still in great shape", think about this: there are quite a few people around that drink like a fish and smoke like an Indian chief, but they're still around at 85 years. Then there are those who lead a similar lifestyle who kick the bucket at age 50. It's all about risk: if you want to increase your chances of living that long, eliminate as many detriments as possible. I might suggest the same theory holds true for engine outboards.
HappyTime	posted 05-05-2003 01:29 PM ET (US) I am not sure I've heard 'windmilling' but my mechanic at The Outboard Motor Shop told me to put my kicker in gear to prevent it form free spinning in reverse while using the main motor.
Tom2697	posted 05-05-2003 03:00 PM ET (US) There are basically two ways to kill gearing. One is to run them without lubricant. Two is to have them partially engaged or to mesh improperly. The only way I can see damage occuring by this windmilling effect is if the gears are clashing as the prop turns (wind resistance is usually not enough to overcome metal to metal contact) or if the lubricant is not touching the gears. It seems to me that the lubrication issue might be logical. It seems that todays' outboards raise higher out of the water and are also more streamlined in the lower units. This COULD mean that the lower unit oil will settle where it no longer provides lubrication to the gearing. Since all props will spin as though they are in reverse while experiencing the windmilling effect, the reversre gears will mesh and wear. Depending on the design of the internal cavity of the lower unit, Mercury outboards could be more susceptible to this problem. A simple fix is to tie the props so they don't spin, put the motor CAREFULLY into forward gear so as not to bend the shifting rods, or, one could always lower their motor so the oil contacts the gears (assuming the skeg does not drag on the ground). BTW - I am not a certified marine mechanic...but I did do a stint as an engineer for an industrial gear manufacturer.
David Jenkins	posted 05-05-2003 10:52 PM ET (US) This is somewaht off-topic, but is there a problem with tilting a power-tilt motor all the way forward while trailering it? While this may or may not reduce "windmilling," it balances the weight of the motor directly over the transom versus having all the weight pulling back on the transom. Do most of you use "transom savers?"
where2	posted 05-06-2003 12:39 PM ET (US) Still looking forward to why this is not a problem in the water, but it is on the highway... In the meantime, here's more on the water scenarios to think about... So, will I have the same problem if I am doing 50mph, and pull the gearshift into neutral? How about if I have dual engines and one of them dies. Do I have to tilt the dead engine clear of the water, or can I just leave it in neutral? (For GeneNJ) In reality, the gearbox in the lower unit looks nothing like an automatic transmission on a car. It's actually less complicated than a manual transmission in car. It looks like 3 gears submerged in oil with bearings and thrust washers around for good measure. I wish I had my OMC manual here so I could scan this simple device. Due to Steve's comment in his original post that said "Why didn't they install that $.05 washer in front of the reverse gear", I suspect it all boils down to a design flaw in Mercury outboards that causes something similar to idling a car with a manual transmission, and pulling the gearshift toward a gear, without pushing in the clutch. However, since you don't have synchros in a lower unit, you directly grind the gears...
kglinz	posted 05-06-2003 12:53 PM ET (US) The reason you can't compare to a car automatic transmission is that the transmission is lubricated and cooled by oil pumped by the transmission oil pump, which is driven by the input shaft. Engine not running, no lube. Same reason you can't "push start" an automatic.
elaelap	posted 05-06-2003 01:37 PM ET (US) I've trailered my boat twice since this thread began, and remembered to put the motor in gear...so what's the problem? Seems a simple enough solution, even if Steve is wrong. Is there any downside? Tony