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Mercruiser 43LX Loss of Power

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chad2021

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"I have a 1993 Bryant 4.3Lx Al

"I have a 1993 Bryant 4.3Lx Alpfa 1 Gen 2 s/n 888xxx. Here is what happened, I was going at full throttle when all the sudden the RPM's revved up and the prop quit turning. Pulled back the throttle to nuetral and tried to shift into forward, engine revved, but would not go into gear. So I shut it down and got towed to shore.

Here is what I've done so far without finding any problems. Dropped the lower unit down, shifted through all gears, prop would lock in the proper positions and rotate the center shaft. Then pulled the rest of the stern drive, U-joints look good, no problem with the male splines of the drive shaft. Looked at the female splines, don't see any probem with that, no metal, no white powder.
I just put the stern drive back together and am getting ready to bolt it back on the boat. The only other thing I can think of is to check my lower shift cables for proper adjustment. ANY other suggestions would be great!
I'm a first time user here, hope I did'nt miss anything."
 
This is the plan

Reinstall

This is the plan

Reinstall the outdrive.

put the ear muffs on and turn the water on.

start engine

look at the back of the engine where the drive shaft from the outdrive comes thru the back of the boat.
You should be able to see the coupler/ hub spinning and the driveshaft spinning also.

If the coupler is spinning and the driveshaft is not then the coupler is bad.

If all is good then it may be the prop hub.

If not the prop hub then put it back in the water and retest the looking for the driveshaft not spinning at the coupler.

Aside from that it could be the upper gear set???

you did not say anything about od noises coming from the outdrive so may not be gears.

The coupler is a aluminium female spline ecased in rubber so the rubber could have "spun" out.
 
Oh and please do not repost as

Oh and please do not repost asking why it wont shift correctly. If you were able to seperate the two halfs and remove the OD then you should be able to figure out the rest.

Thanks
 
"Thanks for the advice, I'

"Thanks for the advice, I'll post my findings once all the above is checked, but I'm only able to work on this in the evenings."
 
"Was getting ready to put the

"Was getting ready to put the lower unit back on the boat, while it was still on the ground I moved the shifter into forward gear (held it) and started turning the prop. While turning the prop the main drive shaft rotate about 3/4 of a revolution, then I felt a slight bump in the prop shaft (kept turning it) and the drive shaft quit moving. I moved the shifter to nuetral and the prop free-wheeled, shifted to rev, prop shaft turns, drive shaft doesn't. Shifted back to forward gear, prop shaft turns but the main drive shaft doesn;t?"
 
"I drained it before I took th

"I drained it before I took the lower unit off, it looked normal, no metal parts in the oil or on the drain plug magnet.

I was looking at a parts diagram of the prop shaft, what are the chances that the cross pin in the sliding clutch sheered off? Would that allow the prop shaft to stay in gear and rotate the prop shaft but not the main drive shaft?"
 
"Taking a guess, driveshaft is

"Taking a guess, driveshaft is sheared where the pinion gear bolts to.Most likely cause is a severe strike within 18 months.Did you hit hard????????????????????????????????"
 
"BT Doctur thanks for the manu

"BT Doctur thanks for the manual link. I have owned this boat for 3 years, haven't hit anything, not even a prop ding, that's what's really bothering me. I don't have the right tools to pull the prop shaft, I'll have to bring this one to the shop and have someone pull the shaft for me, I'll update when I get a look at it."
 
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