20hp Mercury won't idle

[Bill 1970]

Re: 20hp Mercury won't idle

I have to agree with JB. I have a 74 model 200 20hp. Its smooth, powerful, and VERY fast. I can get about 32 mph on my 14 ft lund! Its a great motor. Might be worth an overhaul.

 

[BSDenning]

Re: 20hp Mercury won't idle

Well, I think I'm done working on this motor tonight... I'm going to have to do some thinking on this issue. It's not my motor. A friend brought the motor to me because he knew that I messed around with motors.

 

[BSDenning]

Re: 20hp Mercury won't idle

More bad news... I pulled the head off to take a look at the cylinders to see how much damage there was. It blew my mind away when I took the head off. I'm used to Evinrudes where you take the head off and you can inspect the cylinder walls and the pistons. But, when I took the head off, I was still looking at the spark plug holes (basically, I had just opened the water jacket)! Anyway, there is a crack in the cylidner just to the left of the spark plug hole. Take a look at these pictues. I was thinking about trying JB Weld on it, but then I read on on the JB Weld website that it is not reccomended to use in the combustion chamber or anywhere that the temp gets above 500 degrees. So, what do you guys think? Is this motor done for?

 

[jbjennings]

Re: 20hp Mercury won't idle

I believe you can stick a fork in that one. However, powerheads are a dime a dozen for that motor. It's the electricals and lower units that go first. THere's probably hundreds of those old 70's 20hp motors hanging up at every dealer that's been around since then, all lacking lower units. They're good lower units, they just finally get leaks in the seals due to the mild steel drive shaft getting pitted, and rust to pieces inside. I had one that ran great and was a nice motor, but the gears in the lower unit were horribly pitted. It still ran nice until I sold it years ago.

 

[jbjennings]

Re: 20hp Mercury won't idle

On a side note....
I've got a '73 65hp merc that has jb weld holding the water jackets together--kind of like yours, and it is still holding after probably 20 or 30 6 gallon tanks being run through it. And I could crank it up right now and use it. That being said, I think your powerhead is garbage now.
Sorry,
JBJ

 

[BSDenning]

Re: 20hp Mercury won't idle

Thanks for the info JBJ. Hey, do you know what the white spots are in the water jacket? I was wondering if that had to do with it overheating. Or perhaps it shows that the motor has been run in salt water?

Thanks.

 

[jbjennings]

Re: 20hp Mercury won't idle

It could be calcium or salt deposits. I'm really not sure.
JBJ