Hard knock when shifting into gear

[Heybuddy]

Hey guys ive had the boat out couple times now, been running good but what I don't like is when I shift from neutral into gear there is pretty alarming bang. What is it that's happening? Is it located in the sterndrive? And is it an expensive\easy fix ? Running a 88' Mercruiser 4.3 w\ alpha 1 stern drive.

 

[Bondo]

Ayuh,..... What rpms do you have the idle set too,..??
Should be 650/ 700 rpms, in gear, in the water,....

Alpha drives shift like an outboard, with dog-clutches, which bang into gear to some degree,.....
A normal fact of life,.....

 

[thumpar]

How hard is the "bang"? It is normal for them to clunk.

 

[Heybuddy]

its not a bang to feel just a loud bang im gunna assume its normal but maybe I can dial back my idle screw and see what happens. You guys are always great! experience helps. Thanks

 

[TyeeMan]

I wouldn't set your idle down especially if it's set at the correct idle rpm. Go lower than that and you could see other problems like a cooling problem, or stalling when you come down to an idle or shifting into gear.

As previously mentioned, the alpha 1 drive has a good clunk shifting into forward or reverse.

 

[harringtondav]

....can't add much. Alpha drives engage with a dog clutch. Clunk. Check your prop to be sure it doesn't have excess end play on the shaft. Loose nut or incorrect thrust washer in front of the prop. And don't baby it when shifting into gear. Grinding is bad. A clunk is good.

 

[andrewterri]

Going to lower will make your engine a bearcat to start when its cold.

 

[wahlejim]

The only thing I would add is to go from reverse to forward and see if it is louder or struggles shifting. It could be an indication that your shift interrupt switch is failing.

 

[achris]

The only thing I would add is to go from reverse to forward and see if it is louder or struggles shifting. It could be an indication that your shift interrupt switch is failing.

The problem is going into gear, so the interrupt switch has nothing to do with it.

Chris..

 

[wahlejim]

The problem is going into gear, so the interrupt switch has nothing to do with it.

Chris..

That's why I mentioned going from reverse into forward gear. If the engine wasn't interrupted I would imagine quite a clunk would occur.

 

[achris]

That's why I mentioned going from reverse into forward gear. If the engine wasn't interrupted I would imagine quite a clunk would occur.

Then I suggest you read the original post....

...when I shift from neutral into gear ....

 

[Sea Rider]

It's quite normal for any engine revving at higher idle rpm to achieve a loud clunk noise when gearing forward. A matter to back off the idle rpm screw a bit to soften the clutch/gear engagement if the loud clunk bothers you..

Happy Boating

 

[Lou C]

Hook up an accurate tachometer to the engine and set the idle properly. The shift interrupt system should not be engaging at all when you shift into gear, if so then there is a problem. It should only engage when the shift cable senses load on the outer jacket from trying to get the clutch dog to disengage and that trips the interrupt that momentarily shorts out the ignition to lower the engine idle enough to get it to release. When the idle is set between 500 and 600 on my OMC Cobra (in the water in gear) it shifts with a THUNK but not a bang. Do you have a stainless prop by chance? That is heavier than an aluminum prop and can increase the noise of engagement.

 

[QBhoy]

What prop do you have. Some props in particular make it all the more harsh.
Shouldnt really bang too much, especially in the water.
Out the water, yeah a bit.

I had one particular stainless prop on mine and it wasn’t just as smooth as others.

I know the big diameter 4 blades have a harsher way of engaging.