Shallow water drive question on main engine.

S

Sunbeam

Active member
Can you tell by my recent postings that I've never owned a big outboard before? :mrgreen: (<--- 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
 
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.
 
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.
 
Will-C":ypcqruie said:
I usually only tilt up the motor beyond the slow portion of the trim range with the trim button when idling.
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That's what I was thinking of too. Just idling into or out of shallow nooks and crannies. I also wondered if it might be the way to go if using the engine to load onto a trailer at some ramps (?)

Will-C":ypcqruie said:
Some people with bigger cahonies than I get on plane to get across shallow areas if there is a muddy bottom.
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:shock:

potter water":ypcqruie said:
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.
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Ah, good point. For some reason I hadn't even thought of that (I mean, I did keep an eye on the telltale stream in general, but wasn't thinking of it as a gauge to know how much tilt would be okay).
 
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.
 
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.
 
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.
 
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.
 
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.)
 
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.
 
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 :D
 
potter water":10k40z0r said:
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.
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That's too bad (that even good work would foul up a warranty). If I re-power I'll have to check in to that - I'd definitely favor a brand that allowed me to do my own work (and of course I wouldn't expect them to cover anything I did wrong; but neither would I want them to penalize me for doing something correctly to my own engine).

That said, my current engine is well out of the warranty period -- it's just new to me and I'm still a bit in awe of it (and what it would cost to replace it). Knowing I had plenty to do on the boat, and wanting a professional "baseline," I had all of the initial work done by a shop - luckily I bought the boat near a Yamaha shop I really liked (even if they wouldn't "let" me buy a new engine until I used my current one for awhile ). They rebuilt all four carbs (for some reason letting them sit with fuel in them for years didn't agree with them - shocker!), did a full tune-up, re-placed the impeller and associated seals/gasketry, new fuel filter, drained the carbs, and maybe a couple of other things I don't remember at the moment.

But since then I've bonded with the engine a bit myself, by prophylactically replacing the regulator/rectifier (Yamaha came out with a beefier one that superseded the original), installing a Permatrim ("whee, let's drill a bunch of holes in my new engine!" :shock:), fitting a different prop, and figuring out how to manually bleed the tilt system.

Going ahead, I won't mind taking it to a shop for work when there is one nearby that I like; but I also want to be able to do my own maintenance, as an option. So what I did was get a set of spares to have on hand. If I do use them myself, great. If not and I'm someplace without access to parts then at least I can hand them over to a mechanic. And if there is a shop I want to take it to that has parts, then great, I'll continue to hang onto them as spares.

At least that's the plan. But I won't say that the thought of a shiny new engine doesn't ever enter my head :twisted: So I'm glad you mentioned that about the warranty, as it's something to consider if I do engine shop at some point in time (like say if all the brands don't take the same position on that).

Sunbeam
 
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.
 
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.
 
Even though my engine is well out of warranty (low hours, but not new chronologically), I'm using the Yamaha brand products, at least for now.

I imagine if I researched I'd find that oil is oil (presuming it's specified/rated correctly), but I don't buy enough volume that Yamaha parts are going to break the bank so.... Yamaha it is, at least for now. I stocked up and got a couple of their oil change kits, lower unit lube, Ring Free additive, various gaskets and O-rings for the various drain plugs, internal fuel filter cartridge, etc.

I may very well take it in to a shop for some things, but I like to have parts on hand anyway just in case I end up someplace that doesn't have them.

Now, I should be so lucky as to have that new engine warranty problem :D
 
Generally if you have separate tilt and trim switches then the trim limit is about a high as you should run. If you only have one switch then you will usually have a trim gauge. If you have a I/O like myself then you must pay attention to this gauge as trimming too high is detrimental to the health of your U joints.

Another point to consider when trimming up for skinny water is that it tends to compromise stearage. The closer your "rudder" is to the surface of the water, the less effective it is. Close quarters such as in a marina should be done trimmed fully down.

Your drive is most vulnerable during acceleration(between displacement and planning speeds) and when settling, coming off plane.

Dave, if you plan on coming up Lake Erie to boat in Long Point inner bay - you better start growing some! :P Crossing sand bars and weed beds on plane becomes a way of life here. You must be familiar with the bay to attempt this though. No rocks in the inner bay, but usually at least once during the season, somebody will run up on a sand bar at full speed and get stuck. :cry:

Regards, Rob
 
Robert H. Wilkinson":lcjd78si said:
Generally if you have separate tilt and trim switches then the trim limit is about a high as you should run. If you only have one switch then you will usually have a trim gauge.
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I think I have a combination of both. That is, there is just one trim/tilt switch, and just one cylinder on the engine. However, there are two speeds (operator has no control over them). While in the trim range, the engine moves more slowly (and the sound is different). Then, once it reaches a certain point, it's in the tilt range and moves much faster.

I might have assumed all engines worked this way, but the ETEC 90 I used last fall on Powell only had the one (slower) speed, all the way up - both trim and tilt were the same. Sounds like a little thing, but it makes me appreciate the faster tilt speed on my Yamaha (of course one tilts fairly often on Powell) (and the ETEC is lighter).

Sunbeam
 
As someone who has gotten stuck when using my 2 and 1/2 foot drafting Duffy, I am paranoid of shallow water. The beauty of the Gheenoe was that you could shut down the engine, hop out, and push or drag the boat over the sand bar to deeper water. I had the same question being asked originally and do rely on the stream coming out of the engine as my guide as to just how far I can tilt up. I was at a Marina in Beach Haven NJ this past August where the entry into the marina at low tide was 1.8 to 1.9 feet. I was nervous in my CD 16. I don't understand how the 40 and 50 foot yachts at the marina, some of whom must draft 4 to 5 feet, get around.
 
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