Shallow water drive question on main engine.

Sunbeam

Can you tell by my recent postings that I've never owned a big outboard before?

(<--- Mr. Green is appropriate here).

My question pertains to what I have heard called "shallow water drive," i.e. when you trim/tilt the motor well up for poking into shallow water. (The owner's manual for my engine doesn't seem to have much to say about it.)

Not to make something simple complicated, but on the other hand these big engines don't come cheap, and I sure don't want to wreck anything (like my new impeller...). Do I just trim/tilt until it sounds like it's too far out of the water and then lower it a bit? Can that "fry" the impeller or do other damage really quickly?

My engine has a slower "trim" range and then a quicker "tilt" range, but when at the junction between the two (in other words as I ran out of "trim" and got into "tilt") it still didn't seem to be in true shallow water drive position (but I'm not sure). Is that normal? I guess I was kind of expecting some sort of detente or something. It's been a long (loooong) time, but I seem to remember some sort of lock or setting for that function on the small outboards of my youth (5-6hp, no power anything).

I figured I'd ask you experienced folks rather than experiment and possibly do some damage.

Thanks,
Sunbeam

Will-C

I usually only tilt up the motor beyond the slow portion of the trim range with the trim button when idling. If the exhaust breaks the water (gets louder) I trim it back down a little. Most outboards have a heat alarm which will get your attention and limit your rpms before you do any damage. I have never traveled long distances like this but as soon as I'm out of the shallow water area I drop the motor back down. Some people with bigger cahonies than I get on plane to get across shallow areas if there is a muddy bottom. I would always set your shallow water alarm for a little leeway and check it using a stick and your thumb. Then measure the stick where your thumb touched the water and adjust your shallow water alarm accordingly. Make sure you know how far the bottom of your skeg on your motor's lower unit is from a true waterline. Mark Twin did this differently. Just my 2 cents
D.D.

potter water · Posted: Fri Sep 13, 2013 2:23 pm Post subject:

Main thing is to make sure the engine is "peeing" nicely at any angle of tilt or trim. If so, then you are in good shape. Of course, by definition, shallow water operation is done at wake less, or more often less than wake less speeds. As long as the engine is peeing and the prop isn't cavitating, then you are in a safe shallow water mode and safely tilted. You may still his some bottom, but the prop won't hit. The skeg might, so just because the motor is up a ways doesn't mean there aren't many ways to damage it.

Sunbeam

PaulNBriannaLynn · Posted: Fri Sep 13, 2013 2:51 pm Post subject:

Of course I always try to avoid those really shallow situations where I need to trim up the motors, sometimes its unavoidable.

We got "stuck" this summer trying to get back into the Swinnomish channel near LaConner on a very low tide. There was a sailboat that was stuck in the mud, and a few other boats waiting at the mouth for the tide to rise. I figured this is a C-dory, so I can make it! While I carefully and slowly passed the sailboat, my depthfinder went from 3' down to 1' immediately, and we stopped moving with lots of muddy sediment coming up from my prop. Disgust

I already had one of my twins tilted up out of harms way, so I tilted the other one until the water uptake port was out of the water. I lowered it back down just enough that it was pulling in water again and slowly cruised through the shallowest part. Im guessing the waiting boats were a little envious.

So I wasn't really stuck but it was close! As long as the motor isn't running for a long time without water intake, no harm done. The overheat alarm takes all the guesswork out of that anyway.

thataway · Posted: Fri Sep 13, 2013 4:54 pm Post subject:

During Winter low tides at my home it is not unusual to have about 18" or slightly less over a sand bar at the entrance to our Bayou. As long as the engine is "peeing" I feel safe running the engine, so I take it up significant distance--I can tell by sound when I am at that "point"--and go ahead very slowly. Been doing this for 12 years with no problems--both I /O and various brands of outboards.

If it is shallower than I am comfortable with and the boat is able to float over, I use a "push pole" made out of 1 1/2" PVC pipe 9 feet long, and the other 12" are used in a "T" on the bottom of the pole. The pole is also marked with tape at one foot and half foot intervals, so I can tell the depth in very shallow water where I may not have good depth sounder readings, or risk hitting a rock or stump.

colbysmith · Posted: Fri Sep 13, 2013 10:47 pm Post subject:

Running an outboard for any length of time without cooling water is a mistake, I fried an impeller once by just starting the engine accidentally without water fliw and just running it for a minute. In this situation, the impeller was dry.

thataway · Posted: Fri Sep 13, 2013 11:02 pm Post subject:

Some folks say they have run motors for seconds with no damage, and I'll admit I have occasionally run a motor for a few seconds without water flowing. But there are stories of impellers frying in less than a minute. I always put a little silicone lubricant in the shell and on the impeller when I change it.

Sunbeam · Posted: Fri Sep 13, 2013 11:16 pm Post subject:

That's the thing that I was thinking about as I was experimenting the other day. Before we realized we could just wade in and pull the boat over to the trailer (duh!), I thought we might need to motor up onto it, and I wasn't sure if I should do that with the motor trimmed down. It was at that point I realized I wasn't sure about how the shallow water drive worked, because when I trimmed up to the point where the slow "trim" meets the fast "tilt" it really wasn't that tilted yet..... didn't seem all that shallow. But then I also wasn't sure if I kept on tilting if I would damage the impeller, or just exactly where I should stop.

I suppose it's a bit less likely or quick to cause a problem when the motor has just been running in the water and things aren't starting out dry, but still. That baby wasn't cheap or eaasy to have changed, and burning one up would kind of spoil the day. (Side note: I was surprised to find out how involved changing an impeller is on an outboard because changing the impeller on an inboard isn't usually that bad, and I expect them to be more complicated usually. Anyway, I did discover that it's not something i'm going to carry a spare for and expect to just "pop in" if it's needed.)

potter water · Posted: Sat Sep 14, 2013 12:03 am Post subject:

My twin Susuki's had their impellers replaced last fall by....me...took about 1 hour each from undoing the first bolt to drop the lower unit to putting the last bolt in to snug the lower unit back on. I would not be intimidated by having to do it while on a trip and, in fact, I carry spare impellers with me and make sure that I have the right sockets to do the job.

I'm not bragging, but most of the newer outboards are very straight forward relative to replacing the impeller and shouldn't intimidate anyone who can use a basic set of metric sockets. The only tricky part I ran into was disconnecting the gear shift link between the lower unit and the upper unit.

Take a look on You Tube, and you will see many good videos on replacing impellers on various newer engines.

I would never intentionally run my motor without the lower unit having water available for the impeller under any circumstances and for any length of time.

Sunbeam · Posted: Sat Sep 14, 2013 12:22 am Post subject:

Good info - maybe I built it up a bit too much in my mind.

Too, I'm in "ooh, my new engine -- I don't want to inadvertently wreck anything!" mode. Still have the kid gloves on and I'm a bit in awe of the thing Very Happy

potter water · Posted: Sat Sep 14, 2013 10:47 am Post subject:

If it is under warranty, forget about working on it yourself. Anything you may do to it, good or bad may foul up the small print on your warranty.

Sunbeam · Posted: Sat Sep 14, 2013 1:53 pm Post subject:

potter water · Posted: Sat Sep 14, 2013 9:18 pm Post subject:

I think you will find all brands will have strict small print language in them telling you that if you fiddle with their engine in any way, that they can negate the warranty. In fact most will tell you that if you put a good quality marine lower unit lube in it that doesn't carry "their" brand name on it and you get lower unit problems, they can use that as an excuse to invalidate a warranty repair.

It is just the way things are. Now, if you have a good dealer, he may "OK" you dong some stuff on the engine.

It all depends. Just saying, be a little cautious on brand new engines if you work on them in any way. A call to the dealer is always a good idea to make sure. Write down the day you called, and the name of the person you talked to and file that away if you do get approval.

I've been burned, so, perhaps I'm a little overly cautious.

Just my thoughts.

thataway · Posted: Sun Sep 15, 2013 2:05 pm Post subject:

I always use the "brand" specific oil, filter and lower unit oil, for a new engine for the warrantee period. I keep the receipts and log when I do the oil changes.

In older engines I have drained the carbs, and fogged the engines if in storage for a period of time. I doubt that these type of issues will get you in trouble with a warrantee.