1977 Merc 500 50hp lost power and idle

[JamesR77]

I am new to the in's and out's of outboards so bear with me.

I have a 1977 Mercury 500 50hp. She has been a great motor til now.

A few nights ago I was on my way back from fishing. Was at full throttle, the engine suddenly (fast but gradual) lost power and died. I could start it back up again with the throttle control at full. I could then take it down the river for maybe 1000 yards and she would do it again.

I have removed the carbs and cleaned all the gunk out. Fixed some misaligned gaskets. Fixed fuel bowl leak, checked needles. Nothing has helped.

Alot of the wiring inside has cracked insulation. But I didn't figure that would be the problem cause it has run great for more than the year that I have had it. I would assume that if wires were crossfiring or grounding out It would cut out or not start at all.

From what I have done so far, it hasnt changed much. I can now run at full throttle and it wont die back down. But now I dont have the get up and go that it used to. Main thing is that it wont idle now, and I dont have the "pop" when I gun it.

Any help would be most appreciated. Thanks in advance.

James

 

[JamesR77]

Re: 1977 Merc 500 50hp lost power and idle

Hmm, were's the Mercury love? Did I answer my question already?

 

[BR]

Re: 1977 Merc 500 50hp lost power and idle

James,


I you've removed and cleaned the carbs completely you'll now need to re-tune the mixture. There's also a procedure called a 'link & sync' that should be done. Search this forum for a post by Clams Canino for a good, easy to follow description. Improper carb mixture adjustment would cause poor idle and bad performance out of the hole.

Good Luck!

 

[crappiejig]

Re: 1977 Merc 500 50hp lost power and idle

James, your description of your engine acting up sounded just like my 1975 merc 650,when I lost compression in the #1 cylinder! Hope your situation is different. I would recommend a compression test,easy enough to accomplish and rule out a bad piston. scott

 

[JamesR77]

Re: 1977 Merc 500 50hp lost power and idle

[edit] blah blah blah............Said something sooooooo novice. [deleted]

Now I just need to figure out how to remove the powerhead so I can replace the rings. This appears to be a bit more difficult than I had imagined.

 

[JamesR77]

Re: 1977 Merc 500 50hp lost power and idle

At this point I am looking at possibly a broken reed valve. Still need to figure out how to remove the powerhead. Once that is done I will let you all know what it was.

 

[JamesR77]

Re: 1977 Merc 500 50hp lost power and idle

Just an update......

Looked into the LU and found that it had alot of water in it and was a bit low. Drained and refilled.

When turning the fly wheel there is some squeeking coming from the lower unit. At this point I am to believe that there is something in need of replacement, whether it is bearings or seals do not know. But once I get the repair manual, I will crack it open and check it out. I would think that is where my bogging down is coming from.

 

[rheagler]

Re: 1977 Merc 500 50hp lost power and idle

Water getting into the combustion chamber can cause what you describe also. The leaky cylinder's spark plug will be significantly cleaner than the rest.