Hit a piece of submerged wood

R

RobLL

New member
Yesterday I sped up to 17 knots ensure being out of the way of the Point Defiance ferry, and hit a piece of submerged wood. After a very loud and frightening 'thunk' evidently it or part of it fouled the propeller and the 2006 Suzuki 90 very briefly revved up and then idled (or I idled it). I turned the engine off, and raised it out of the water. There was a piece of wood (2 by 2, and 18 inches long) floating between the engine and stern. The propeller did not have any dings or scratches. I restarted and gingerly raised the speed back up to 14 knots. It all seemed well for the rest of the trip, some 2 hours more.

Could anyone explain what likely was happening, and do I need to go in and do any maintenance? I suspect some sort of safety clutch enabled itself.

I sure felt green in more than one way.
 
Is it possible that whatever hit it the engine lifted it out of the water briefly resulting in the over-revving? I believe most engines have an over rev limiter that would limit the over revving. Then maybe when you slowed and raised the engine out of the water whatever was trapped there cleared and things were fine. If the prop didn't have any dings or scratches, it seems likely that only the lower unit was hit and lifted out of the water a bit.
 
hi Rob,

Here's guessing, you got out of the way of the ferry :wink: and made it home ok :) so that parts good.

After looking over your prop, any damage, dings, or scrapes? The size of the piece would make a pretty good thunk ok and could do some damage. I doubt that it would be big enough to cause the engine to lift, (which would be one reason for the over rev) and then it would jump the log and slam back down into place again. This could happen but it would require a pretty substantial piece of wood to do that.

Another possibility could be, (and I think this would be more likely), that the piece you found, stuck cross-ways in front of the prop, causing a big cavity in the water, an air pocket behind the stick and in front of the prop, causing it to loose bite on the water and allowing it to rev up.

You may find some mark on the forward side of the leg or on the transom where the end slammed the boat when it originally made contact. You might get lucky and not have any dents. If you don't find any and have no new vibrations, be thankful and remember to keep a really good watch from here on.

Harvey
SleepyC:moon

1_10_2012_from_Canon_961.highlight.jpg
 
I would check the lower unit bolts and change the fluid.
On a flat day, run the boat at top speed safety just to check the ride, smoothness and prop hub.
 
Do you have the XHS system on the prop?

http://www.amazon.com/gp/product/B0000T ... ge_o02_s00

I just installed this on my Yamaha 50. I read that it can save a prop by spinning on the rubber/plastic insert rather than damaging the prop. What I'm not sure of is whether the system can actually allow the prop to momentarily spin free when it hits an obstruction and then recover without any damage to the rubber/plastic insert. The system might allow the revving and return that you experienced.

I need to do more research on just what I've installed!

Mark
 
I seriously doubt an 18 inch 2x2 did anything other that a good thud. I would bet you had cavitation going on during the collision with it hence the high RPMs. If a little ding on a prop or even a misplaced hull rivet can cause this, just guess what an 18" stick will cause. I've hit stuff like that before in my C-Dory lots of times - it happens. In my river jet-skiff, I hit stuff like that all the time. After a good inspection (maybe), I just motor on.
 
RobLL":2po0bm2r said:
Yesterday I sped up to 17 knots ensure being out of the way of the Point Defiance ferry, and hit a piece of submerged wood. After a very loud and frightening 'thunk' evidently it or part of it fouled the propeller and the 2006 Suzuki 90 very briefly revved up and then idled (or I idled it). I turned the engine off, and raised it out of the water. There was a piece of wood (2 by 2, and 18 inches long) floating between the engine and stern. The propeller did not have any dings or scratches. I restarted and gingerly raised the speed back up to 14 knots. It all seemed well for the rest of the trip, some 2 hours more.

Could anyone explain what likely was happening, and do I need to go in and do any maintenance? I suspect some sort of safety clutch enabled itself.

I sure felt green in more than one way.
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Cavitation!!. A 1/2" diam. piece of bull kelp will do this to my 25. If there are no dents or paint chips etc. in the prop blades you are good to go.
The only fail safe is the pressed in rubber between splined hub & prop blades.

:wink: :wink: :lol:
 
I think you're fine. It's always kinda unnerving to hear or feel something out of the ordinary though. A similar situation happened to me as well.

Btw, you should add some pics of your boat to your photo album. Join the "cool kids table"!! Lol!
 
Lots of kelp and wood debris all the way Friday and Saturday. A lot more bother than the three ferry routes I passed. Between Everett and Tacoma there are six.
 
Rob, Regardless of what you find after closely inspecting for damage, please post a followup describing what you found and what you intend to do. Thanks......
 
Was the prop SS? If so, you can have a substantial encounter with a piece of wood, and not show any obvious external damage.

I don't know what happened--and I doubt if any of the rest of us really know. Most outboard props have a shock absorbing 'hub" which will slip--some are interchangeable, so one can buy cheaper props, but use the same hub. Generally when the hub slips, it will continue to slip--but there are cases where it slips right after contact, and then seems normal. The fact that you got back to 14 knots suggests that there is not a spun hub, but I would still consider that prop suspect.

The wood you found may have been part of a piece of larger debris, which did cause the motor to cavitate--but most of the big motors are locked down--and don't kick up as smaller motors do, if not locked down.

I always carry a spare prop, thruster washer, castle nut, and cotter pin--as well as a wrench and needle nose pliers--in case I have a spun hub. I have had it happen a couple of times.

To those who say a 2 x 2 will not cause damage--I'll have to disagree. It can in some cases--and I had to buy a new lower unit for an I/O after an encounter with a less than 2" "stick" ruined the gears in the lower unit.

At this point, I would agree with the lower unit oil change Especially check the fluid, and magnetic plug for flecks of metal, which might indicate gear damage. Look again very carefully for any evidence of prop damage, and do a run out of the prop shaft (pull the prop, and see if there is any deviation of the prop shaft as you turn the motor over slowly.)

Be sure and carry that extra prop--just in case! (As well as some form of a kicker, to get you to safely.)
 
I still haven't found any info on the web as to whether the XHS system destroys the urethane bushing if the prop spins when it hits something. It seems like I would find replacement bushings for sale and stories of people replacing them if they are a wear item. It also seems like Michigan Wheel would mention carrying a spare cartridge. Hmmmm.

I just bought a prop wrench for the boat. The floating prop wrenches looked interesting, but the reviews were that they are disposable, sometimes before you finish the job. I need 22mm for the Yamaha and I opted for an offset double box end ($7 from China). That way my wrench can have a lanyard attached to the 19mm box. Better than trying to retrieve floating wrench is to have it tied to my wrist.

http://www.ebay.com/itm/151915490092?_t ... EBIDX%3AIT

Only issue is whether the offset is deep enough. I'll know in a month, which is the estimated shipping time.

Mark
 
Has anyone ever had to change a prop before? On the water I mean. I can imagine that the swaying and rocking of the water would make it a less than desirable condition. Would it be possible to change it from the splash well? Or would you have to be in water? If possible the best way would be to beach the boat stern first maybe, at least then you could minimize the swaying.
Even if you were able to get back to a dock it would still be hard to change it, no? Could one stand on the dock and reach over to the main motor??

I hope this never happens to any Brat! Changing a prop on the water seems like an enormous headache....but doable of course.
 
I'm not an engineer, but I would say they went to great lengths to make sure it doesn't slip. Slipping is bad generally. I'm with Bob on carrying a spare prop. I carry three - one for each motor. And I have had to use spares on occasions. I have lost a couple on uncharted rocks in PWS anchorages, and one just out of the blue started slipping away - reason unknown. I have also wrecked a complete lower unit as I hit a log of 1/2 floating hemlock hiding in the whitecaps about 30' long and 10-12" round - I nailed it square fortunately but it REALLY hit hard. It cracked the lower unit on my old and trusty 28' bayliner. It still made it home somehow and I know I was lucky. If you boat long enough, you're going to hit something in the water.
 
I will be checking with a local company, having moved boat from Everett to Bremerton. I need to get the bottom paint redone anyway. While I am not mechanical I do need to learn to change a prop.

ps - I was once in Alaska 45 miles up a river in flood stage without transmission or oars. Managed to idle in reverse back to the village. Don't want to be without a working motor again.
 
South of Heaven":1v69g5qr said:
Has anyone ever had to change a prop before? On the water I mean.... If possible the best way would be to beach the boat stern first maybe, at least then you could minimize the swaying.
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I've never done it "out in the middle" of the water; but I did change props two or three times at Powell (was checking out WOT RPM's with various props) and I went stern to the beach, tilted the engine up, and stood in the shallow water to change the prop. I slung a bucket to hold parts and tools, plus had spare prop nuts, wrenches, etc. aboard just in case anything was lost in the water. Was easy. (There was no surf of course and I watched for wakes.)

On the prop and hitting the wood, most of my engines (before the C-Dory) have been the old fashioned kind with just a shear pin, but I would (as mentioned by others) want to check the rubber hub piece on yours. I've heard of cases where it gets damaged and then will run the boat until you really "give 'er," at which point it will slip due to the damage. Kind of like a deteriorating clutch (in a car) where it's fine if you baby it a little, but will slip going up a big hill or something. I know you said you went to 14 knots, but I'd still want to make sure it's 100% good. (That said, I don't have a lot of experience with them, as noted above.)
 
I have had that form of cavitation happen as well. Like playing a dodge the log video game out there sometimes.

We hit some good ones with Aurelia. Ari, has only hit some small knockers.

Greg
 
I have done a lot of work backed up to a dock as well. So long as the water is calm, it works fine and even the permatrims on Aurelia were installed on the water. Well, now that I think about it, everything I ever did to that boat was done while in a slip.

Back on topic, We once hit a long curved piece of wood about 8ft long by 3in thick and it got cradled between the twin outboard legs on Aurelia. We were doing about 20 knots at the time and it was like someone hit the brakes and turned the wheel at the same time with tremendous force. The motors both also revved from cavitation. It sent loose items flying and got my attention to a greater degree than anything boating related before or since. I really though we hit a whale or something else massive but not fixed or were caught in an anchored net. I simply pushed it free with the boat hook and we were on our way with no damage. It was the shape of the wood and the way it got stuck that caused such a strange braking/turning affect.

Greg
 
Mark, I have that rubber hub on my Solas 4 blade prop. I think to spin it, you'd have to chew up the rubber pretty well. Seems to me the plastic hubs would break, and continue to spin. The rubber seems to be a little heavier material, and while it provides a little more flex and vibration reduction, I would think it could allow the prop to make a few revolutions, but not to the extent the original thread starter was talking about. My vote for that would be with the cavitation caused by debris in the way. I would definitely check the hull, engine and prop for any other damage however. I hit something when we were in the San Juan Islands 2 summers ago, and didn't see any visible damage, but still had some vibration afterwards. Changed the prop out and we were fine. I guess it doesn't take much of a ding to put a aluminum prop out of true! Makes me a little more nervous about hitting anything with the thin fiberglass hull in the bow! Colby
 
Heck, I don't even think I have been boating until I hit something...anything will do....the dock, stump, rock etc.

Joel
SEA3PO
 
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