1988 Johnson 15 - More Wonderous discoveries

gamarines2

Petty Officer 2nd Class
Joined
Jun 14, 2007
Messages
102
Alright. Rebuilt carb and replaced all fuel lines. Carb didn't look all that gunked up, and lines were in surprisingly good shape. Rebuilt and replaced lines anyway. I got to thinking more about my original problem. I had an overheat and assumed it was my impeller (never before replaced it). But when I went to replace it, the impeller and water pump housing were in impeccable shape. Replaced with the parts I had bought anyway. So I ask myself....self, why did my boat overheat?

So I went to check the thermostat. Honestly, I never even imagined that a motor this small would even have such a device. Top two bolts came out with no problem, almost TOO easy. Bottom one twisted off easily and remains in the cylinder head. First question. Any suggestions for removing a stainless bolt? Use traditional come out tool? Will that work, or should I even try?

What came out into my hand when the housing cover came out? A severely rusted couple of springs, and what looked like what have been at one time a functional thermostat. Will obviously replace that, but now, I wonder if there aren't some parts of that deteriorated mess clogging up a water passage somewhere. How do I even begin to run that to ground? Any suggestions will be greatly appreciated.
 

tx1961whaler

Vice Admiral
Joined
May 31, 2008
Messages
5,197
Re: 1988 Johnson 15 - More Wonderous discoveries

I'd drill out the busted bolt and re-tap the hole. Real Cobalt bits; left twist a plus. Too easy to break off an EZ-Out in there
 

Bob_VT

Moderator & Unofficial iBoats Historian
Staff member
Joined
May 19, 2001
Messages
26,065
Re: 1988 Johnson 15 - More Wonderous discoveries

If I remember right.....it is in the head? I would remove the head and actually use a drill press with the cobalt bits.....

With the head off it will give you the chance to examine the piston, decarb and have access to more of the water jacket to see if it is clear.
 

AlTn

Commander
Joined
Mar 9, 2010
Messages
2,813
Re: 1988 Johnson 15 - More Wonderous discoveries

if there's enough screw remaining to grip with some vice grips...heat the aluminum area around it with propane or mapp gas and grip the screw as close to the head as possible and you should be able to back it out....would suggest you chase the threads with a tap afterwards and use a marine grade antisieze on the new screws
 

gamarines2

Petty Officer 2nd Class
Joined
Jun 14, 2007
Messages
102
Re: 1988 Johnson 15 - More Wonderous discoveries

Wound up pulling off the head, drilling out the bolt and tapping in new threads.

Replaced head gasket. Compression numbers went up and even. ran great without load...can't wait to get it on the lake and open her up. Here, fishy, fishy, fishy....
 

AlTn

Commander
Joined
Mar 9, 2010
Messages
2,813
Re: 1988 Johnson 15 - More Wonderous discoveries

good deal
 
Top