Drive line vibrations

Sea ray 88

New Member
May 6, 2018
16
Boat Info
1988 Sea ray 21 foot with 4.3 merc cruser alpha one gen one outdrive
Engines
4.3
I have a 1988 sea ray with a 4.3 Merc cruser with a alpha one out drive an I am getting a bad vibration at low speeds. I rebuilt the out drive so every thing Is new in the gear case. My prop has a few marks in it but nothing that looks to bad. This is the first boat I have ever owned so I don't know much about them. Does any one have a idea on where the vibration would come from or what I could check. Thanks
 
Could be a wide range of issues. Get someone that has boat experience to go for a ride in it.
 
Could be a wide range of issues. Get someone that has boat experience to go for a ride in it.
That's the problem I don't know anyone that has boat experience an the local boat mechanic charges 95$ an HR an I don't have a ton of money to have a mechanic to look at it. I was trying to fix it my self. I figured someone on here could at least tell me some things to check out.
 
Q&A's could go on for a long time, probably worth 95 buck to take him for a ride.
 
Assuming that’s your engine is in tune and running smoothly, I’d look at prop balance and wear of the internal splines in the coupler to start with.
 
Does it go away at higher RPM? I there any noise? What about when you trim the motor up or down or turn left/right does it change?
 
The motor runs great. Yes it goes away the faster u go. I replace the rubber bushing inside of the prop. When u trim it up an down it don't stop the vibration. The splines on the the brass sleeve that centers the prop look fine an the shaft that holds the the prop on look fine also. Turning left or right also don't seem to change it. It's just a bad vibration at low speeds. It shakes every thing in the boat.
 
Did you have the vibration before the drive rebuild?

For the marks in the prop... what does "not too bad" mean? Post a pic.
 
Did you have the vibration before the drive rebuild?
Idk I bought the boat used an the person I got it from said it was water ready but when I changed the oil in the out drive it just came out of every where so when I tore it down I found all the seals leaking and all the bearing pitted with rust so I just did a full rebuild. I keep checking the oil in it every time after I take it. To see if there is any water or metal in it an there is nothing.
 
How does it run other wise, what kind of RPMs do you see at WOT. Vibrations caused by outdrive problems or bent propellers don't usually go away at higher RPM usually get worse.

If you are not reaching WOT RPMs between 4500-4800, I would start looking at the engine itself, ie are all cylinders firing etc?

Plus what Dennis said, if the vibration showed up after the drive rebuild then you at least know where to look.
 
I am getting about 4300 rpm at wot. The motor starts right up no problems and runs great.
 
I am getting about 4300 rpm at wot. The motor starts right up no problems and runs great.
The prop does have some small dings in it but nothing that looks to bad to me.
 

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Is it the camera, or is there a significant “wave” on the edge of the blade in the first picture?

Do the other blades have the same “wave”?
 
Is it the camera, or is there a significant “wave” on the edge of the blade in the first picture?

Do the other blades have the same “wave”?
No just that one Blade.
 
No just that one Blade.
Would that wave in the blade cause it to shake the boat really bad a low speeds. Sorry this is my first boat an I don't know much about them.
 
I would Start with the prop. Have it fixed or replaced before tearing into anything else.
 
So, without knowing the history, it's really tough to say. It could be anything from a bent prop shaft to the prop to an error in the rebuild to something engine related. But, that prop is definitely more than "not too bad". In addition to the wave in one of the blades, is that a different blade that appears shorter than the other two (shaved down)? It appears to be "flat" at the tip.

Get a new prop or send that one out for repair. Get that done, that report back.

FYI... $95/hour is pretty cheap for marine labor. If it's a reputable dealer, even better.
 
So, without knowing the history, it's really tough to say. It could be anything from a bent prop shaft to the prop to an error in the rebuild to something engine related. But, that prop is definitely more than "not too bad". In addition to the wave in one of the blades, is that a different blade that appears shorter than the other two (shaved down)? It appears to be "flat" at the tip.

Get a new prop or send that one out for repair. Get that done, that report back.

FYI... $95/hour is pretty cheap for marine labor. If it's a reputable dealer, even better.
How do u know what prop to buy. Is there a way to look up what prop I need for my boat?
 
I only had the boat out 3 times doing some test runs an trying to work out the bugs before summer. The first time I had it out I didn't notice a vibration at all an the second time I didn't notice it either but this last time it just all the sudden it started. An it just seem to get worse.
 

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