Boat goes into gear, prop doesn't spin

[findinghomer]

Hi guys, this is a 1997 Mercruiser 5.7 v8. Long story short, I got stranded on the water last night, after running fine all day bc It wouldn't go into gear. I was on plane, and the boat made a cavitating sound. Assuming it was just cavitation, I just carried on. but the third time it stalled. Never to go back into gear again. I got the boat to my driveway and checked some things. When I put the boat into gear , the prop does lock to whichever direction respectively. So it appears that the shift linkage is shifting the lower unit properly. But when you start the boat and put it into gear the prop does not spin. I pulled the outdrive, and then separated the lower unut. With the lower unit off, I can turn the prop and I can hear it spinning the impeller as it turns the vertical drive shaft. So it appears everything is working as it should down there? Everything appears physically fine from the out drive. Nothing obviously broken. Before I pulled the outdrive, I checked to see if it was drawing in water to the engine. It doesn't appear to be. I am afraid it may be the engine coupler, is there anything else I should look for? Or is there any othet indication for me if it is the coupler? I peered in there with a flashlight and it looks ok but I don't know how sensitive those things are. Any help would be appreciated thanks

 

[Fishermark]

... Before I pulled the outdrive, I checked to see if it was drawing in water to the engine. It doesn't appear to be. ...

You have found your problem, more than likely. The coupler is gone. You can probably look into the bell housing and see the coupler splines (or lack thereof) since the outdrive is off. If it is bad, you will need to pull the engine to replace the coupler. Then you will need to align it when reinstalling.

 

[findinghomer]

You have found your problem, more than likely. The coupler is gone. You can probably look into the bell housing and see the coupler splines (or lack thereof) since the outdrive is off. If it is bad, you will need to pull the engine to replace the coupler. Then you will need to align it when reinstalling.

Looking through the gimbal with a flashlight, the coupler splines look fine. I opened up the upper unit gear casing. There's definitely some stuff broken in here. Is a rebuild of an upper unit for the professionals?

 

[findinghomer]

Nm. For the price I will pay for the parts, I can get an aftermarket SEI assembly for only a little more. save the headache lol

Oh, but how do I find my gear ratio?

 

[Bt Doctur]

You need to find out what part went bad.
Your prop, is it the rubber hub or the plastic hub?
Was the oil level in the drive up to the threaded hole?
Did you see 4 inch long slivers of aluminum when you removed the drive?
Was the engine recently removed?
When was the engine alignment cheked last?

The coupler is under $250.00 and the drive is around $1600 .Being a 5.7 your gear ratio can be 1.47 or 1.50

 

[Bt Doctur]

Opps, didint see the part about the gear damage

 

[Fishermark]

You ought to consider replacing the entire outdrive instead of simply buying a new upper. When the upper unit grenades, it sends particles throughout the drive and the lower unit is probably not far behind.