89 19ft bayliner with a 4cylinder mercury outboard cant get it to shift in to gear after a freind shifted it from forward to reverse with out stoping it killed moter an now wont go in forward or reverse took off botte

Good morning,
Sounds like the cable for gear shift needs to be adjusted .
Remove control cable or linkage for gear shift .
Move gear manually into neutral.
Adjust cable length to fit into that position.
Hope that helps you
Regards Gordy

check that there is not a shift lock to prevent accidental movement and engagement of gears
could be a button to press first or a lever to move
ring a mercury service center and ask them

Seems like your are describing a outboard motor. If so, the Boat section of Fixya may have more experts that you need. You would want to avoid turning any screws on the carburetor body. The externals on the linkage have some adjustments like throttle stops.

The linkage on boat shift mechanisms are tempermental. They usually combine 2 functions on 1 control lever. They are synchronized that when the transmission shifts from neutral to forward and neutral to reverse the idle speed is low. This keeps the gears from grinding and takes the shock out of the shifting process.

Another thing different than on a car engine is the effect of the propeller on engine rpm. You can change the "in gear"
rpm for both directions by changing prop size and/or pitch.
This also means you can over-rev the engine by having the wrong prop on the boat. There are engine rpm "stops" for the high end too, but some just rely on using the correct prop. As what you may be experiencing with a "stall" can be brought on by

A word of caution. The inboard/outboard engines can have the same problem as outboard engines. The shift levers are synchronized with a pivot system and adjusting the throttle can interfere with the shifting.

You may be able to view youtube videos by searching for these topics.

That is best. A very short pause is fine.

I’m happy to assist further over the phone at https://www.6ya.com/expert/bill_f6ca18ca1db028ed

Outboard won't go into reverse ?? - General Discussion Forum ' In ...

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Aug 9, 2006 - 8 posts - ‎7 authors
There's 2 cables that go into my outboard. ... It would have forward just fine but it would not shift into reverse. Assuming it's a wheel boat does the throttle handle go intoreverse but reverse doesnt work or does it not even ... Here are instructions to recover your old idofishing.com or idohunting.com account:.

Boat won't go in reverse - Lake-Link.com

www.lake-link.com/forums/boats-motors/.../Boat-wont-go-in-reverse

Sep 23, 2013 - 4 posts - ‎3 authors
Fishing Boards - Boats & Motors: Boat won't go in reverse. ... Forward seems to be working OK, but reverse just won't engage. ... I'm not sure if this is something at the throttle control end or something wrong at the motor. Any thoughts ... Looks like there'sa piece missing that's supposed to hold that in place.

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www.thehulltruth.com/boating.../526873-help-will-go-reverse-but-not-f...

Jul 30, 2013 - 8 posts - ‎5 authors
Whether you're researching a new boat, or are a seasoned Captain, ... and it was notengaging fully into forward gear, but into reverse just fine. ... I'm a little dumbfounded as to why it will lock the prop when it's not running, but won't go into forward gear when it is ... While your there, change out the bellows. Mercury 125 won't go into reverse - The Hull Truth ...
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Should first have some one look at the shift in the engine compartment while some one runs it from the control box. If no movement, would be the cable.

Then undo the bottom drain plug and see if the oil is full of metal shavings. Yikes

Last see if the shifter going to the lower is actually moving when you shift.

mercury and others have a "sawtooth" cut for forward gear so the prop will rachet spin backward when dry tested, and a square clutch dog for reverse, which when it finally engages locks the prop in reverse. and will not spin in either direction.

So when you shift--- snap in in gear-- do not ease it in gear, as it will wear the dog out faster.

If you have a control box, your shift cable end may be loose. It is swedged on to the connector and can break there, then stick, so check for a broken cable by holding the engine end when some one tries to shift it. If it pulls loose, you need to inspect it for breaks and loose anchors or connections.

If it is a manual shift, you may have a connector screw loose or missing. There is a posiability the shift cam in the lower is worn, or the center rod running inside the prop shaft is worn to the point it won't catch the clutch dogd. (shift quick/ don't rattle into gear.)

Most mercurys natural state was in forward gear, as they ate their clutch dogs you could get a little more service from them by under adjusting reverse- giving forward a little more life. It was a marginal fix and could end up with your problem.

With your lower unit off have someone shift the engine into forward while watching the gear shift select shaft's rotation,let gearshift remain in forward,now place your lower unit in forward and reinstall. In the future just put engine in forward when installing a water pump as there won't be a need to move gearshift

You did not tell us if you have a small outboard or if you have remote shift controls. If you do have remote shift controls you can try reversing the cable ends if it is a 2 cable system or disconnect the cable at the engine. By disconnecting the cable at the engine you isolate the problem to the motor. Then you can grab the shift lever manually at the motor and see if it will now go into reverse. Some remote levers lock out reverse if the choke is engaged or if you are new to this boat there may be a button to push on the throttle to allow reverse to engage.