Motor shakes at full throttle

[19732009]

I have a 1988 19ft bayliner with a 125 force motor outboard,at full throttle it shakes bad if I let off a lil it goes away and someone told me it may be cavatating to my understanding that is where you get an air pocket around the prop,and it also looks like to me that the motor doesnt sit far enough in the water when all the way down.The top of one of the propeller blades is about 4inches above the bottom of the boat when motor is all the way down.The motor is the originally motor that came with the boat,just wondering what i can do to fix this and also i have a 13-17 prop on it now

 

[Splat]

Re: Motor shakes at full throttle

Where is the anti ventilation plate in relation to the bottom of the boat?

It should be approx 1inch above the bottom of the boat. Any higher and trouble could arise.

No to insult, because I don't know your experience, but are you using the tilt trim properly? Not trimmed out to far?

If the motor is too high, often they can be lowered if there are positions available on the transom bracket, or the use of a jack p-late may be in order.

Cavitation is in fact when air is sucked into the prop stream. However vibration can be caused by many things, including a dinged or bent prop. Has this problem started recently? or always been there?

Not to worry, we'll get you fixed up.

Bill

 

[grego]

Re: Motor shakes at full throttle

guessing here! most outboards, from full up position, "Kind of stop" at the TOP of the full up position of the TRIM. You have to hold down the trim button to get the engine to go all the way down to zero trim. Just guessing.

 

[19732009]

Re: Motor shakes at full throttle

Not sure what the anti ventalation plate is,there are 2 fins going horizontal,doesnt matter if trim is all the way down still does it and i did try a new prop and still does it,it starts shaking about 4000rpms at 30mph then rpms will shoot up high and speed stays the same

 

[coolguy147]

Re: Motor shakes at full throttle

ya sounds like its ventilating

or a possible spun prop hub?

 

[WAVENBYE2]

Re: Motor shakes at full throttle

Is this a new problem or did you just buy the boat??

 

[Capt'n Chris]

Re: Motor shakes at full throttle

Have you experienced a smooth running motor and properly performing boat prior to this problem? Do you have any idea what led up to this? You cannot determine the correct motor height or depth by making reference to the top of one of the 4 blades, but you can, as others have suggested. He may not know it, but he will now, a bent prop can lead to a bent crank...and so on. If it has been run like that for some time now, it's anyone's guess. None of us like to be the bearer of bad news, but I'm wondering if the damage has already been done.

 

[19732009]

Re: Motor shakes at full throttle

yes i do now a lot about bots and moters just never had this be for. I wonder if the shaft was bent i have had the boat for 1 year now and it did it from day one. The moter runs good and has good compression all over 120

 

[WAVENBYE2]

Re: Motor shakes at full throttle

I wonder if the shaft was bent i have had the boat for 1 year now and it did it from day one.

You can have it checked out pretty cheap if not free, The prop guy here puts a device on mine to check the shaft to make sure it wasn't bent and checks the props too. It's worth checking out to help with your troubleshooting check list, At least you'll know and go from there.

 

[JB]

Re: Motor shakes at full throttle

Is there some part of "(not engine topics)" that is confusing?

Moving to Force troubles.

 

[john from md]

Re: Motor shakes at full throttle

You need to run a straight edge from the anti ventilation plate on the engine to the transom of the boat. It should contact the boat at or 1 inch above the keel.

As to a bent shaft, they will vibrate at all speeds. Don't ask how I know this.

John