1971 Mercury 500 50hp Intermittent Tell Tail Flow

[riverratjody]

I recently purchased a used boat and it was flowing from the tell tail great. Trimmed it up the other day to go through some stumps, then it quit flowing. Brought it back to the house and removed the lower unit and found parts of an old impeller in the very bottom and floating around in the impeller housing. I put it back together and used it a few times, and it stopped again. I pulled the lower unit again and this time I used a piece of stiff wire with a small hook, stuck it up the copper tube, and pulled more impeller parts that were stuck at the top just before it entered the engine. It flowed for a few more outings, but it stopped again today. Seems to happen after I tilt the engine when I go through shallow areas. Not much mud where I go so it's not that. I fear there may be impeller parts that have gotten up into the water jacket/head and when I trim it, the parts move and it blocks the path. I have tried blowing into the pee hole, but can't seem to get anything out. I've blown both ways with water and air. Anyone have any ideas? Thanks.

 

[mercurymang]

Re: 1971 Mercury 500 50hp Intermittent Tell Tail Flow

You didn't say and we can't assume but did you replace the impeller?

 

[riverratjody]

Re: 1971 Mercury 500 50hp Intermittent Tell Tail Flow

I did not. It was replaced by a Merc dealer a week before I bought it, just a few months ago. The old impeller was destroyed and nothing was left but the center hub. I found some of the vanes floating throughout the lower unit. I would think the Merc dealer would have found this. I am afraid parts of the vanes are inside the motor. Is this possible, and how do I go about getting them out? Thanks.

 

[jbjennings]

Re: 1971 Mercury 500 50hp Intermittent Tell Tail Flow

Remove the water jacket cover and take a peak. That motor won't have a cylinder head, just a water jacket cover. Be careful you don't break any bolts off, and if so DON'T try to get them out with "EZ outs". If you can't find the offending pieces, and you probably won't, you may have to remove the powerhead and check the water tube, water tube grommet, water jackets, etc. I would also consider checking the exhaust covers/gaskets. If it's ever been overheated, those could be a problem. Also, I'd remove the exhaust cover and replace the poppet valve and thermostat--if they're under the exhaust cover like I suspect. Broken bolts are the norm there, you just have to learn to deal with them. You may find a corroded baffle plate under that exhaust cover. Replacing that stuff is just part of the joy of owning an old outboard.
GOod luck,
JBJ

BTW, those impeller vanes you found in the water tube are definitely a problem. There could be others still in the tube. How are other vanes "floating around in the lower unit"? THey should only be a problem if they're in the pump housing, water tubes, or powerhead.