Touching the bottom with your props while idling...Bad?

Skuza

Skuza

Well-Known Member
Nov 1, 2006
1,456
Lake St Clair, MI
Boat Info
400 Sundancer
Engines
7.4L Horizons
Over this past weekend I ventured into a local bay for a raft-off party. Well the bay is very shallow and you either have to run in on plane or idle all the way in. Since I was towing the dinghy I preferred to idle in. Well on the way out later that day I was idling out and started scrapping the bottom. I felt the props start scrapping on the bottom and the boat shuddering. I had to throw it in neutral a couple of times because it was freaking me out. Im wondering how bad the is for the props, shaft struts and transmissions? After getting out into deeper water eventually I ran up to about 2,800rpm and did not feel any vibrations so I don't think I tweaked the props. The bottom in the bay is all sand. I know I should check the strainers after stirring up this much sand. Whats everyones thoughts and experiences with touching bottom? If its sandy such as where I hit am I probably safe? I'm sure that not going too fast helps also but just that shuddering feeling really shudders the nerves! :smt009
This was in Muscamoot Bay for anyone that knows Lake Saint Clair! :wink:
 
Into neutral "a few times"? So, on hitting bottom the first time, you kept going? One time might not have caused trouble, but repeatedly?

I just spent $340 to have two props fixed from skimming the sand ONCE. The only way I could tell something was wrong was a lack of top end. No vibration but going WOT wouldn't push the boat along to it's usual top speed. Struts and shafts are OK, just 'lipped' the props. Then it was another $600 getting it pulled out of the water, props removed and washed.

If you can get a hand down to them (when the engines are off, of course) try feeling around the tips of the blades. You'll probably feel them being slightly ragged or even bent over a bit. Mine were. See if you can hit your usual top speed, if not then prepare for prop work.... and stay out of the shallows!
 
If no rocks were involved I wouldn't worry too much. There is a spot on the river I run "IN THE CHANNEL" at low tide had about 2 feet of water. You have to idle thru (with the drive up) when you catch it at dead low. Same bottom, sandy muck. Experienced it MANY times and have never had an issue.
 
All I can do is make a comparison with SS props on an outdrive where I have had similar situations. In all cases except for maring the finish on the outdrive and scratching the props, I never had anything bad happen to them. Now if you hit something solid, then that's a different story.

With an inboards your rudders hang down quite a bit lower than your props so I would think if you were idling and your rudders didn't hang you up, you are probably OK. If it was my boat and I didn't feel any vibrations then I would just wait until my next haul out to have a look at them. But maybe some of those folks with inboards might have a different perspective for you.
 
When you hit bottom, the boat will definetly shudder, if not down right stall out.

If it was all sand, no doubt you polished your props.
But, it doesn't take much of a rock to put a ding in the prop, which will cause problems.

Check out the props, and look for dings.

If nothing obvious, run her at various speeds, and take note of any vibration.
If no vibrations, consider yourself lucky, and join the club! :wink:
 
Skuza-

On a sand bottom, the boat will shudder quite a bit before the props actually come into contact with the bottom. By all means, STOP when this happens. The props can be damaged by even the slightest contact with the bottom, especially if you are in gear. If you actually grounded your props, there is damage. It's now just a matter of how bad. Good luck.
 
Its time

To get a diver to check out things. That you hit bottom several times would concern me alot. Even without vibrations you were also "dragging" non spinning props when you went to neutral, causing them to "plow" through the bottom. This puts a lot strain on the shaft log, cutless bearing and shaftlogs. Besides the prop damage the shafts also could be bent.

After a diver finishes, check the strainers and by all means open the raw water pumps to check the impellers, you could have torn a few vanes loose by sand basting them.

Just curious, did you know how shallow the water was while you were running?

Good luck ...
 
Skuza said:
Over this past weekend I ventured into a local bay for a raft-off party. Well the bay is very shallow and you either have to run in on plane or idle all the way in. This was in Muscamoot Bay for anyone that knows Lake Saint Clair! :wink:
Click to expand...

I'm surprised that you can even get a 40 ft boat into muscamoot! Lucky for you, it's a very sandy bottom there. I basically grew up on that bay - back when the lake level was high enough to go into both big muscamoot and little muscamoot.

I agree with checking out the edges of your props and checking for vibrations at various speeds. Consider yourself really lucky! :smt101
 
Just raise the prop up a little until you are not scraping anymore.. i used to jump out and push it if it was shallow enough.. BUT then i got the garmin 440c and i never EVER hit shallows again!!!! I was the king of the prop scrape.. I used to do it like it was my dam job! with pride!!.. be safe.

-c rock
 
cr0ck1 said:
Just raise the prop up a little until you are not scraping anymore.. i used to jump out and push it if it was shallow enough.. BUT then i got the garmin 440c and i never EVER hit shallows again!!!! I was the king of the prop scrape.. I used to do it like it was my dam job! with pride!!.. be safe.

-c rock
Click to expand...

Now that's the best advice I've heard here in awhile... "raise the props up".. Why didn't I think of that? Geez... sometimes the answer is right in front of you. Need to find the button that does that.
 
Uh crock, you can't raise the props on an inboard. Sterndrive I/Os, sure, but when they're inboards the props and struts are fixed. That and you generally don't have stainless props on an inboard. You *want* the props to fail if you hit something. On a sterndrive there's the chance it'll move upwards enough to deflect the impact. Or the hub inside the prop will help. No such luck on inboards. It's props hard-mounted onto fixed struts, all of which are hanging down beneath a very heavy boat. Props are cheap to fix compared to ripping a strut out of the bottom and sinking it.

Like I said, I skimmed a sandy shoal ONCE, stopped the boat and let the current drift me back off. It ended up causing enough of a 'lip' to the props to kill WOT speed and incur haul out and prop repair costs.

When you have the props pulled make sure they also check the shaft and strut alignment along with cutlass bearings. With luck (like mine) it'll only be prop damage.
 
Skuza,
You will want to inspect your dripless shaft seas as well. If the cooling water for the dripless seas had sand then you may have damage and a water leak about to happen.

I did this last year in Potomac River Mud. As the Cummins churned away, I called Frank W and he told me to run her at idle speed for a mile or two to let the dripless shafts flush themselves out at low RPM. So I did. 200 hours later, no drips, knock on wood. Sure shined the props up real nice. As others have said, inspect all your impellers as well.

Call me conservative, but now if there is less than 3' under the wheels at low tide Truly Blessed II ain't going there.

Tough to kedge 14 tons of Sea Ray against tide and wind.

regards
Skip
 
Four Suns said:
cr0ck1 said:
Just raise the prop up a little until you are not scraping anymore.. i used to jump out and push it if it was shallow enough.. BUT then i got the garmin 440c and i never EVER hit shallows again!!!! I was the king of the prop scrape.. I used to do it like it was my dam job! with pride!!.. be safe.

-c rock
Click to expand...

Now that's the best advice I've heard here in awhile... "raise the props up".. Why didn't I think of that? Geez... sometimes the answer is right in front of you. Need to find the button that does that.
Click to expand...

Where is that trim switch again on that 400 inboard cruiser ?? :lol:
 
cr0ck1 said:
sory didnt know that the outboards you could not do that with..
Click to expand...

That's right. Anything over about 28 feet and they put outboards on them. Don't make yourself look so silly next time before you check out the boat and know they have outboards because outboards on these bigger boats are very different than I/O's.
 
I think his intentions are good....... however confused. Not that I'll be taking any advice from him, ever. :)
 
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