Replace or Repair, where to start?

[craig newton]

Overheated my 84 Mercruiser 5.7L. Didn't notice until it was badly smoking so I'm sure it's damaged even though it was running as good as usual. After it cooled, I pulled the thermostat and poured in a gallon of anti-freeze, and put it back together. It started right up and I headed for the docks at a fast idle. Was back at the docks in just a few minutes and it was running fine but by then it was smoking again. Since it continued running well, it didn't seize up, no knocks or noises I'm hoping it's something I can repair. I've looked for instructions as to where to start to determine the extent of the damage but haven't found any.

 

[alldodge]

After it cooled, I pulled the thermostat and poured in a gallon of anti-freeze, and put it back together.

Using AF then your motor is closed cool? I'm not understanding that you wouldn't just remove the radiator cap

I'm thinking its not closed cool and the impeller went bad so the pump wasn't pumping any water. If this is the case then pouring AF down the thermostat just ran back out

Being a Merc you should have a Alpha drive. When was the last time the impeller was replaced?

 

[craig newton]

Using AF then your motor is closed cool? I'm not understanding that you wouldn't just remove the radiator cap

I'm thinking its not closed cool and the impeller went bad so the pump wasn't pumping any water. If this is the case then pouring AF down the thermostat just ran back out

Being a Merc you should have a Alpha drive. When was the last time the impeller was replaced?

Thank you alldodge. This is my first I/O. It is an 1984 5.7L 260hp repowered in 2003 with an alpha 1 gen 1 outdrive. You were right, it is not closed cool as I was told. And the impeller went beyond bad. Alot of it had melted to the shaft as well as the inside of the housing. The outside of the plastic housing was burnt and the guide tube looked like a half burned candle. Any ideas how this got so hot or what I should check next.

 

[dwco5051]

More than likely ran dry. It does not take long to look like that if ran out of the water or not on properly fitted muffs.

 

[alldodge]

If its not pumping water because the impeller vanes have broken off. With no vanes the block empties of water and the exhaust gases fill those areas so everything gets hot.

Being a 84 (and your pic) it should have a MR Alpha drive. I would replace the entire pump assembly with a kit 46-96148A8

Do back flush everything to find all the pieces

 

[craig newton]

I'll get some new muffs, instal a new kit and look for some youtube videos on backflushing. Again, thank you for your advice.

 

[alldodge]

Back flushing just means, remove the hoses and use a garden hose to flush them out back toward the drive one at a time. Your just looking for pieces of the impeller. Could be most all are gone, just checking

 

[craig newton]

I did a back flush with the lower section off and found a couple small pieces of what I'll assume to be the impeller. I got the kit you suggested as well as a new base and installed it all. I haven't tried to re-attach it back to the upper section yet because it's a lot harder to turn the verticle shaft than I remember. I can still turn it with one hand (barely). When I turn the small shifting gear clockwise and turn the verticle shaft clockwise the prop spins in a clockwise direction. When I turn the small shifting gear counter clockwise and turn the large verticle shaft clockwise the prop turn in a counter clockwise direction. Does this sound right?

 

[tank1949]

Thank you alldodge. This is my first I/O. It is an 1984 5.7L 260hp repowered in 2003 with an alpha 1 gen 1 outdrive. You were right, it is not closed cool as I was told. And the impeller went beyond bad. Alot of it had melted to the shaft as well as the inside of the housing. The outside of the plastic housing was burnt and the guide tube looked like a half burned candle. Any ideas how this got so hot or what I should check next.

sound like someone ran it w/o muffs on?

 

[alldodge]

I did a back flush with the lower section off and found a couple small pieces of what I'll assume to be the impeller. I got the kit you suggested as well as a new base and installed it all. I haven't tried to re-attach it back to the upper section yet because it's a lot harder to turn the verticle shaft than I remember. I can still turn it with one hand (barely). When I turn the small shifting gear clockwise and turn the verticle shaft clockwise the prop spins in a clockwise direction. When I turn the small shifting gear counter clockwise and turn the large verticle shaft clockwise the prop turn in a counter clockwise direction. Does this sound right?

It shouldn't be hard to turn but new seals does make it a bit harder. Rotate the shift foot to a point where the prop locks in the counter-clockwise direction. When the prop locks the shift foot should be facing straight forward.

Once there, the lower can be put together with the upper

 

[nola mike]

Before you put it back together, check out the water pocket cover in the upper. With that overheat it may be melted as well.

 

[craig newton]

I appreciate your advice nola mike. I need all the help I can get. I did put it back together but then I couldn't shift it from forward to neutral or reverse so I took the lower section off. Not sure where the water pocket cover is but I don't see anything else melted. I'll check some diagrams to locate it. Right now, with it out and the shift shaft turned clockwise, the prop spins freely in both directions with no effect on the main verticle shaft. With the shift shaft turned counter clockwise the prop spins freely clockwise and turns the main shaft counter clockwise when turned counter clockwise. ??????????

 

[alldodge]

With the shift shaft turned counter clockwise the prop spins freely clockwise and turns the main shaft counter clockwise when turned counter clockwise. ??????????

May need to understand what spins freely is? If shift shaft is rotated full CCW then the prop will turn CW without the drive shaft turning, but you should hear and feel a click, click, click as the prop rotates

 

[craig newton]

By spin freely I mean the prop spins with no resistance or no effect on the main drive shaft. It does make that click click sound when I turn the prop CCW with the shift shaft turned CCW. If I turn the prop CW with the shift shaft turned CCW, the main drive shaft turns CCW.

 

[alldodge]

Your good to go

 

[craig newton]

What could I have done while putting it back together to cause the shifting problem at the remote. I had the remote in forward position, the shift shaft turned CW and turned the prop slightly CCW to lock. After it was in, I got in the boat and couldn't bring the remote back to neutral to start.

 

[alldodge]

Lets go back to post 12
You said

With the shift shaft turned counter clockwise the prop spins freely clockwise and turns the main shaft counter clockwise when turned counter clockwise. ??????????

If the shift shaft is rotated full CCW and its facing straight forward toward the bow then your good.

Now your saying shift shaft is CW and the prop locks CCW

 

[Scott06]

What could I have done while putting it back together to cause the shifting problem at the remote. I had the remote in forward position, the shift shaft turned CW and turned the prop slightly CCW to lock. After it was in, I got in the boat and couldn't bring the remote back to neutral to start.

With an r, mr , or alpha gen one drive when you split the halves of the drive you need to make sure the lower is in fwd and the shift arm in the upper is facing fwd when you out the two halves together.
there is a short splined shift shaft sticking out of the lower, i think you need to turn it clockwise fully and make sure it is in fwd before putting the halves together, if this is good when you slide the drive with remote in fwd u should be good

 

[nola mike]

I appreciate your advice nola mike. I need all the help I can get. I did put it back together but then I couldn't shift it from forward to neutral or reverse so I took the lower section off. Not sure where the water pocket cover is but I don't see anything else melted. I'll check some diagrams to locate it. Right now, with it out and the shift shaft turned clockwise, the prop spins freely in both directions with no effect on the main verticle shaft. With the shift shaft turned counter clockwise the prop spins freely clockwise and turns the main shaft counter clockwise when turned counter clockwise. ??????????

Look into the upper from the bottom, it's the plastic piece where the copper pipe fits in.

 

[alldodge]

With an r, mr , or alpha gen one drive when you split the halves of the drive you need to make sure the lower is in fwd and the shift arm in the upper is facing fwd when you out the two halves together.
there is a short splined shift shaft sticking out of the lower, i think you need to turn it clockwise fully and make sure it is in fwd before putting the halves together, if this is good when you slide the drive with remote in fwd u should be good

Your correct my bad
Shift shaft full CW
Prop CCW and shift shaft facing forward