Overheated 1970 Johnson 115HP

Dan Beisel

Petty Officer 3rd Class
Joined
Sep 3, 2003
Messages
76
Can someone start me off in the right direction here? I have a 16' Jolly Roger w/ 115hp Johnson.<br /><br />My last boating trip ended poorly. As we were cruising up river my wife said the engine was smoking. I, of course told her that it was just residual smoke left over from the Sea Foam I poured into it a couple weeks before. As soon as I finished that sentence however, I smelled burning electrical. I looked down and saw my "hot" light on and before I could shut her down(the motor, not my wife!), she shut herself down. The antics that took place after that are for another forum.<br /><br />The engine was extremely hot to the touch and had melted any wire that was near it. I assume that the water pump went out and overheated everything. I haven't touched the boat since returning it home (about 7 months ago).<br /><br />I have a repair manual that's pretty good, but it doesn't have anything about rebuilding motors. My question is: does anyone have any suggestions regarding a detaied rebuild manual or where do I start tearing it apart to see what damage I've done?<br /><br />I have done restorations on cars so I have a pretty good basic understanding of mechanics, but I've never torn a motor down and rebuilt it.<br /><br />Thanks in advance.<br />Dan
 

reeldutch

Lieutenant
Joined
Feb 2, 2004
Messages
1,340
Re: Overheated 1970 Johnson 115HP

first retorqeu your cylinderheads and check your compression before you start to tear your motor down.<br />if the compresion turns out ok you might be lucky.<br />after you do the compression check look for the cause why it overheated.<br />but i'm only a do it yourselfer outboard dummy.<br />ask around further.<br /><br />good luck hope you didnt do to much damage<br /><br />reeldutch
 

Cricket Too

Lieutenant Commander
Joined
May 14, 2003
Messages
1,732
Re: Overheated 1970 Johnson 115HP

Sorry to hear about your engine man, that sucks. There should have been an overheat alarm that went off, apparently it didn't work. I would start by seeing if you can get it running again and then check compression to see what your dealing with, if it shows up bad then I would pull the heads off and see what kind of damage there is indside the cylinders. Try to get your hands on a factory manual, their pretty good for rebuilding, and it will be good for putting the new water pump in as well. You should fix that overheat alarm once you get the motor back up and running. Good luck.
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: Overheated 1970 Johnson 115HP

It's best not to let an engine sit after a problem such as that. Being that hot, I would strongly suspect that the head gaskets are shot which would allow water (whatever water there might be) to enter the cylinders.<br /><br />However, if the engine isn't seized, remove the cylinder heads and clean the surfaces both on the heads and block. Install new head gaskets, then torque the head bolts to 18 to 20 foot pounds starting with the center left bolt, then the center right bolt, then the next lower bolt of the same (right) side of the head, then continue on in an ever widing circle.<br /><br />And tighten all the other bolts, screws, and nuts that you can find on the powerhead. No question that many of them are loose due to overheating.<br /><br />Install a new complete water pump, not just a impeller.<br /><br />Replace that idiot warning light with a warning horn of some kind.<br /><br />Of course repair the damaged wiring. Now, if the engine runs as it should, fine. If not, then you can concentrate on rebuilding it.
 

Dan Beisel

Petty Officer 3rd Class
Joined
Sep 3, 2003
Messages
76
Re: Overheated 1970 Johnson 115HP

I guess the manual people don't want to give you all the answers in one book, otherwise you'll never buy another one. I heard the library may have some also.
 

Dan Beisel

Petty Officer 3rd Class
Joined
Sep 3, 2003
Messages
76
Re: Overheated 1970 Johnson 115HP

Thanks you guys!<br /><br />I knew I could count on this forum for sound advice from people who have experience.<br /><br />I'll start working on it as soon as I get some free time and post the outcome. Gotta get back out on the water!<br /><br />Dan
 

Dan Beisel

Petty Officer 3rd Class
Joined
Sep 3, 2003
Messages
76
Re: Overheated 1970 Johnson 115HP

Today I pulled the heads off the motor. The side that got heated had some crud at the inlet of the water passage which probably caused the overheating. Other than that one spot, the passages were clear. The good news is that the engine didn't seemed seized, I turned the flywheel by hand and the cylinders moved in synch and the prop moved in gear! Also, the cylinder walls looked really smooth although the tops of the pistons and head ports were all carboned up.<br /><br />Anyways, I appreciate the advice and I'm feeling pretty good so far. What should I do to get rid of all the carbon build up?<br /><br />Thanks,<br />Dan
 

phatmanmike

Captain
Joined
Oct 24, 2003
Messages
3,869
Re: Overheated 1970 Johnson 115HP

i had EXACT same prop with my 1970 85 ve johnson... overheated, went home, got sad, drank whiskey and sobbed...<br /><br />BUT...<br /><br />and this is a BIG BUT...<br /><br />it was ok.. still turned over and still had compression...<br /><br />i didnt find out mine was ok untill after i had sold ALL parts from it, now i just have this big giant powerhead starring at me... its for sale on ebay right now.... my ebay name is"myoutboards" go see
 

Bass Runner

Senior Chief Petty Officer
Joined
Apr 2, 2004
Messages
746
Re: Overheated 1970 Johnson 115HP

First of all a 1970 didn't have the alarms the new motors do. First i would change the water pump and flush the cooling sys (make sure the rubber gromet on the water tube isn't torn up). Check the compression then i would start it up and watch it real close see if one side gets hotter than the other. Having the heads off you can see if it has a blown head gasket or not.
 
Top