Ever lock-up a water pump impeller??

[SeaRay]

We were out boating the other day and I let my wife drive. She was pulling the kids on the tubes and did a panic stop when they wanted off because she thought something was wrong.

She over shot moving the throttle into neutral and went into reverse. Not terribly hard but it killed the motor.

When we restarted the engine it had a terrible squeal. I was afraid that she hurt the coupler or the drive unit so we got towed into a boat ramp.

After we got home I looked the engine over a little closer and I discovered that the squeal was just the belt as it was pulled over the water pump pulley, which wasn't turning at all as the motor ran.

I disconnected the belt and turned the impeller pulley by hand. After I got it past a tight spot I was able to turn it easily. I put the belt back on and the engine ran great.

Afterwards, I did take the impeller apart and it looked fine. But I went ahead and put a new impeller in, just to be safe.

I am not sure why it got bound up. All I can figure is the engine must have bumped backwards just enough after the abrupt stop to reverse the fingers on the impeller and then they kept it from turning.

Any other ideas??

 

[springer3]

Sounds spot-on in regards to the impeller, but reversing the engine does a lot a bad things. I have not done this on a boat, but when a car spins on the race track (or on the street for that matter), you need to get the clutch in instantly or else the driven wheels run the engine backwards. Here is what can happen. Hopefully none of this applies to your case:

Running the engine backwards reverses the oil flow through the oil filter. That will back-flush the contaminants into the sump. How new is the oil filter?

You engine air intake got pressurized by engine reversal and can get damaged or contaminated. If your engine has a mass air-flow sensor (MAF), the sensor can be damaged by exhaust sucked in when the engine did its reverse.

Almost all engines have a timing chain tensioner that does not like runnng backwards. Running backwards loads the timing chain tensioner in a way it is not designed for. Listen carefully for timing chain noise in case the tensioner was damaged.

Final worry on our marine engines is the presence of cooling water in the exhaust. You may have gulped a bit of water when the engine reverese. In Iowa you were likely in fresh water, and that passed harmlessly.

Sorry - do not mean to alarm. If you have normal operation next time out, you are probably going to be just fine. You may want to take it easy for the first 30 minutes or so until you confirm everything sounds and feels normal.

 

[Sea Gull]

Are you saying that by rapidly throwing the transmission into reverse you were actually able to cause the engine to stop and then restart in reverse rotation?

 

[highslice]

Are you saying that by rapidly throwing the transmission into reverse you were actually able to cause the engine to stop and then restart in reverse rotation?

:wow::wow::wow::wow::wow::wow: I had the same question.

I throw my engine from forward into reverse all the time to stop my forward momentum while docking. I am 1000% certain that there is nothing I can do to to "make my engine run in reverse". Now, a panic stop followed by reverse could lead to water ingestion, but that's a whole other can of worms.

 

[cdefreit]

While docking at slow speeds no problem, but it sounds like she threw it in reverse doing some speed. I can believe that if it stalled the engine, then there may have been enough momemntum to turn the engine over a little bit in reverse (probably not much but enough to flip the rubber impeller in the pump). Just my 2cents.

 

[highslice]

okay, I'll go with this. The back pressure on the exhaust caused by water rushing into the through hub exhaust killed the engine. Maybe the water pickups ingested some air from the cavitation caused by the sudden change in direction of the prop somehow messed with the impeller. I still can't see anything that would make the engine run backwards...:huh:

 

[cdefreit]

Not "run" in reverse, I don't believe a 4-stroke can run/start in reverse, but the forward motion over the prop and the drive suddenly been thrown in reverse stalled the engine and may have just caused to to rotate in reverse a very small amount, I'm not even talking one stroke, just that slight bump, might have had the effect that OP is talking about.

I've never seen or heard of it happening, but it sounds reasonable.

 

[springer3]

Are you saying that by rapidly throwing the transmission into reverse you were actually able to cause the engine to stop and then restart in reverse rotation?

Gas engines cannot run backwards. They can be forced to turn backwards against their will. A car that swaps ends during a spin has the drive wheels turning in the opposite direction, and will power the engine backwards. I was speculating that at high hull speed, the propeller will get powered by the water, and if the transmission was forced into reverse, you might reverse-turn the crankshaft until the boat slowed down.

I think it takes a big turn backwards to reverse the impeller vanes. It might have been just a 1/4 turn (90°) or several turns. The former would do no harm to the engine. The latter might cause problems.

 

[K-9]

:smt021:smt021:smt021:thumbsup:

 

[douglee25]

4 stroke engines can't run in reverse due to the valve timing. 2 stroke engines on the other hand can run in reverse. How do you think the snowmobiles get reverse gear? The engine physically runs in reverse to do that. It's pretty cool if you've ever seen one.

Doug

 

[Jimf1234]

4 strokes do run in reverse in marine applications, bigger boats with twin screws will have one regular and one will be counter rotation. They do have a different cam shaft and the ignition timing is reversed though.

As far as I know you can't bump one in reverse and have it start though.

 

[SeaRay]

Wow!! Lot's of replies....

I don't think the engine actually ran in reverse. I think the sudden stop more or less made it "backfire" and it turned slightly the other way.

At least this is the only explanation I have for why the impeller knotted itself up.

I ran it with the muffs on for a few minutes and all seems fine. The only odd thing I noticed is that there was a black stain in the driveway after the water dried up. It looked like a film of carbon from the exhaust?? I thought it might have also been pieces of the water impeller, which was part of the reason I replaced it. But I didn't see any thing missing form the impeller or the housing that would have caused that??

I had a 2-stroke motorcycle that would run in reverse. The timing was off just right that if you kicked started it (in the correct direction) it would backfire and actually run the other way. It would run just fine, rev up and you could actually ride the bike in reverse. You could even throw a roost under the bike!!