Lower unit freezing and cracking?

[Cricket Too]

Has anybody actually ever had this happen to them in the winter. I have heard my whole life about if there is any water in the L/U it could freeze and crack the L/U case.

I leave my boat in the water until about January, and most of the guys here who do, usually start leaving their engines down in the water starting about now, to keep it from sitting in freezing temps and having it possible freeze. I hate to leave my engine in the water, and last year it grew so much crap on it, an the paint on the prop started chipping off.

Wouldn't there have to be a lot of water in the L/U and also wouldn't it have to be separated out from the oil, in order to freeze up enough to crack a L/U case?? And if you have that much water in the L/U, you have a big problem.

I just got my L/U re-sealed in the Spring, so I have to assume I have no water in my L/U, and if I do see some milk shake come out when I change it, I won't be happy, seeing as how it cost about $600 to get it re-sealed.

I do not want to leave it in the water, but just wanted to see if anybody actually ever had one crack, before I go and leave my engine out of the water this winter.

 

[5150abf]

Re: Lower unit freezing and cracking?

Ya it can happen, if the lower is full of water.

As long as you have good lower oil in it there is nothing to worry about.

You should change your lower unit at the end of the year as a maintanece thing, it also helps you keep an eye on the health of your lower, I change mine at the end of the year and check it before every trip by just cracking the drain screw, if oil comes out it is fine, if you get a couple water drips you need to find the leak.

Lower oil is $4 a quart, a lower is $1400, no brainer.

 

[Chinewalker]

Re: Lower unit freezing and cracking?

Seals or not, if you have a through-hub exhaust lower unit then water can sit in that exhaust outlet cavity when tilted up. Depending on the motor, that could be as much as a quart or so. If that freezes you could conceivable crack the unit. Far easier to scrub the unit periodically than it is to replace a lower unit...
- Scott

 

[kenmyfam]

Re: Lower unit freezing and cracking?

Agree. Don't take the risk !!!!

 

[tashasdaddy]

Re: Lower unit freezing and cracking?

to answer your question, yes they can crack. the water in the lake or river, is usually warmer than the air, that is why your neighbors keep their motor in the operating position, the water in the power head drains in that postion. while water can be trapped in the head, when the motor is tilted, and possibly, cracking the block also.

 

[Cricket Too]

Re: Lower unit freezing and cracking?

Thanks for the responses. I understand the theory behind leaving the engine in the water, I have done it many times....all last winter and for years before that.

I usually leave my engine down for 15-20 minutes when I get back to the dock to let the powerhead drain out, so it's definitely not full of water, I'm more concerned with the L/U.

I have heard that they "can" crack, been hearing that for the 30 years that I have been running and working on my outboards, but I have never heard of it actually happening to somebody.

I have never seen enough water actually be in any of my L/U's to the point where it would be a freezing risk.

I get what Chinewalker is saying about the prop shaft cavity when tilted up, but since that's not an enclosed/confined space then it would seem any freezing water would have room to expand and not crack anything.

I know all the thoughts and theories on the cracking issue, I have just never heard anything about it ever happening to anybody, not that I want it to, it just seems like it would take a whole lot of water in your L/U to freeze and expand enough to crack the L/U case.

5150abf.....the nylon crush washers on the drain and fill plugs are one time use washers, if you crack your drain plug before every time you go out, you are most likely letting water into your L/U, as that seal isn't working correctly after the first time you open it. Just some advise.

Anyway, I hate leaving my engine in the saltwater for 2 months, but I also don't want to damage anything. It just seems that it would take a lot to crack anything.

Thanks, I appreciate anybody's opinion or view. Just looking for a discusson.

 

[tashasdaddy]

Re: Lower unit freezing and cracking?

Cricket Too, wait till spring, as every spring here on the forum, there will be many post where people have cracked lowers, and cracked blocks

 

[Cricket Too]

Re: Lower unit freezing and cracking?

Really? Wow OK, well then I guess you answered my question. I will do a Search on here for specific threads on it.

I was hoping that since I got it re-sealed, and there should be minimal, if not any, water in my L/U, that I wouldn't have to let it sit in the saltwater this fall/winter.

I notice a lot more engines up than down in the water, but that could only mean there are a lot more people that don't know what they're doing that ones that do.

Thanks.

 

[matt2002]

Re: Lower unit freezing and cracking?

I've often wondered the same thing.In my case if I tilt the motor down it gets jammed into the bottom during the really low tides we get in the Winter.
I figure if I let the powerhead drain and then tilt the motor up I could always pour an anti freeze/water mixture into the exhaust hub to be extra careful.
I bought a used boat that had a 225 Mariner on it.Never thought to check the l/u oil.Well I guess it filled with water because after the Winter I noticed the lower unit case ruptured.

 

[junkyardwarrior]

Re: Lower unit freezing and cracking?

In the 15 years I've been wrenching on Yamaha's, I've seen about 5 or 6 broken "foots". All due to freezing water. Mostly on the 25ESH motors (2 stroke). Water gets in and tends to freeze, then expands and pushes the shaft assembly out of the foot breaking the ears off the bearing housing. Pretty easy fix...usually about $150 but it could have been avoided. And keep in mind that it really doesn't get THAT cold here. low 20's is about the coldest it ever gets, with some occasional teens in the dead of winter.

 

[twostroke87]

Re: Lower unit freezing and cracking?

What I have seen, most commonly when I spent my earlier years working on used boats, would be not so much that there was actually already water in the gear oil, but instead, a perfectly sealed gear case tilted up (i/o or outboard) lets water sit the exhaust passage and down towards the bullet.

The water would then freeze and usually it was 50/50, sometimes the cracks were harmless to the gear oil, you just risked losing your propshaft carrier nut, and all the insides as well, or the crack would bypass back into gear oil, causing a leak.

 

[Frank Acampora]

Re: Lower unit freezing and cracking?

Couple of years ago I bought a Merc 115 "Tower of Power" Really cheap because it was stored in the tilted position for a couple of years. Rainwater collected inside the case behind the prop. It froze and cracked. Through a couple of freeze-thaw cycles, the crack extended into the gearcase. Water entered and displaced to oil. Everything inside the gearcase was rusted beyond use. The only thing I salvaged off that lower unit was the skeg. Out of the whole engine, I salvaged a good block, starter, and the skeg. Everything else was scrap metal.

 

[Silvertip]

Re: Lower unit freezing and cracking?

As a minimum you are flirting with a broken prop hub, exhaust housing, or lower unit housing if you tilt the motor out. An outboard needs to be vertical to drain properly. Since the lower unit was IN the water when you tilted it, it can still trap water in the water pump housing and other cavities in the lower unit. Leave the motor down. Lake/river water that is not frozen, will not freeze in your lower unit. When you pull your boat out of the water, then and only then does it drain completely. If you need to prove this this theory that even an uncapped cavity can burst, fill a soda bottle nearly full of water and stick it in your freezer. Yes it will expand vertically, and there is a good chance it will split the side of the container as well. If you fill a tapered container, wider at the top and narrow at the bottom, then you may get lucky as the taper allows horizontal as well as vertical expansion. Since water freezes from the top down, the bottle theory should now make sense. Then consider the shape of the cavities in the lower unit -- as they may consist of many "expensive" shapes.

 

[Cricket Too]

Re: Lower unit freezing and cracking?

Well this post completely served it's purpose!! Informative and knowledgable people explained exactly what can and will happen. My motor will be in the water for the rest of the time until it's pulled in late December.

Thanks to Chinewalker and the rest who pointed out about water sitting down behind the prop in the prop shaft, and cracking prop hubs and more.

Matt2002....I usually only submerge the lower unit itself, just until the anti-ventilation plate is just submerged in the water. That keeps some of the midsection out of the water and I also get some very low tides at times where I have about a foot of water under the boat, so it will keep the skeg from touching the bottom, if you only submerge just the lower unit instead of putting it all the way down.

I figure if just the L/U itself is in 45 degree water then nothing inside it will freeze. I usually let it sit fully down for about 20 minutes or so after I get back to the dock so that the powerhead drains down, as well as some unburnt oil.

Thanks again to everybody for all the professional knowledgable responses, I appreciate being able to find out an answer to a simple question from people who know and are willing to share.

Thanks,

Mike

 

[tashasdaddy]

Re: Lower unit freezing and cracking?

on an outboard, when leaving it in the water, i like to tilt it all the way up, and then back down, this relieves any air pockets and allows any trapped water to drain.