Hit a Stump

[Derner]

Hi my friend has a 1989 Evinrude 48 SPL and we recently hit a hidden stump below the surface of the water with the propeller. Since that event, we cannot go faster than about 10 MPH no mater how fast we race the engine. We replaced the propeller thinking we spun the hub inside the old propeller. The new propeller (at the same pitch and diameter) does the same thing. No mater how fast we race the engine, we cannot go faster than about 10 MPH. We checked to see if the motor had slipped upwards and checked the tilt to see if we were drawing air but it doesn’t seem to have moved or be adjustable. Could a dog-clutch in the lower unit cause this to act this way, or is this more serious? We are stumped!

 

[Silvertip]

Re: Hit a Stump

You need to be a little more specific about what you mean by "racing the engine". If you mean the engine is actually running wide open when the throttle is wide open but the boat is moving slowly, that's one thing. If you mean the throttle is wide open but the engine doesn't seem to be running wide open that's another. If the prop you bought was used it may have a spun hub as well.

 

[Derner]

Re: Hit a Stump

He had purchaced a brand new prop for the boat. When I refer to "racing the engine" I do mean the engine is actually running wide open when the throttle is wide open but the boat still is moving at about 10 MPH, whereas, prior to that event we could go about 30 MPH with the throttle wide open. The engine works the same as it did before we hit the stump, however we are still stuck doing about 10 MPH.

 

[Rodznreelz]

Re: Hit a Stump

A similar incident happened to me. The problem ended up being a frozen bearing in the lower unit. Drain some of you lower unit oil and see if it charcoal black or has a burn't smell.

 

[Chinewalker]

Re: Hit a Stump

The stump isn't by any chance stuck to the bottom of the boat, is it?<br /><br />Another thing - it is possible, depending on how hard you hit the stump, that the splines in the crankshaft gave out and they are now slipping on the driveshaft. Can you turn the motor over by hand and hold the propeller from turning? Make sure the ignition is off, or better yet, pull the plug wires off the plugs so it doesn't remove someone's digits... A block of wood between the prop and lower unit housing may help hold it from moving while you try to turn the flywheel...<br /><br />- Scott

 

[Silvertip]

Re: Hit a Stump

What Chinewalker said is one possibility, the other similar failure is pinion slippage on the other end of the drive shaft.

 

[Derner]

Re: Hit a Stump

I want to thank all of you for your input. We isolated the problem with the boat itself, not the lower unit. The actual problem was an upwards 4" dent at the back of the boat causing the flow of the water to lift the back end of the boat causing the prop to draw air. After we fixed the dent, we can now achieve normal speeds. Again, I want to thank all of your for your valuable input.<br /><br />Thanks