Did I kill my motor?

schwar74

Cadet
Joined
Nov 28, 2010
Messages
17
Well, I seem to be able to screw just about anything up. I pulled my lower unit off my 1974 25 hp Johnson a couple days ago to check the dog and the gears, and I apparently didn't get the water line back in the right place. I was out hunting this morning and it overheated and died. :(:(:(:(:( The paint peeled off of the lower cylinder head. It wouldn't crank immediately, but I could turn it over later after it had cooled off. It did not start however.

Is a compression test going to tell me if there's a huge problem? Or should I just go ahead and pull the head to look at the cylinders? If I do pull the head, do I just look for scoring on the cylinder walls? Is there a chance of damaging the valves? If the cylinders are wrecked, should I just scrap the motor? (It also needs a new FWD gear and clutch dog). I can't imagine its easy to replace pistons and to have the cylinders bored.

Thanks for your help.

Scott
 

bktheking

Vice Admiral
Joined
Jul 29, 2008
Messages
5,057
Re: Did I kill my motor?

Chances are compression is ZERO, head is warped and head gasket is blown. Is the motor still free and rotating, if so it should be ok. While it`s apart check the stat, thermostats don`t like overheated motors. Replace and recheck compression. Then fix the water tube issue.

PS- no valves in a 2 stroke.
 

milliesdad

Petty Officer 2nd Class
Joined
Dec 20, 2010
Messages
168
Re: Did I kill my motor?

New head gasket, make sure head mating surface is flat- 1 sheet emery cloth on a piece of glass, figure 8 pattern till it's even- as above, t-stat and make sure you get the water tube in right next time. And test run in a garbage can before going out again. Water 3/4 up the lower unit.
 

schwar74

Cadet
Joined
Nov 28, 2010
Messages
17
Re: Did I kill my motor?

Thanks for the quick response.

Is there any trick to getting the water line in the right place? On my 15 hp, it seemed to just want to go in the right place. I suppose putting it in the upper port first, then mating it up w/ the lower port as the lower unit is going back on is the thing to do.

Does this seem like a probable explanation for the overheating? Is there another common explanation?

It was about 15 deg F this AM when we were running the first time. Any chance of something having been frozen?

I swear I saw water spitting out of the outlet that's above the main exhaust port. I thought this meant that there was water going through the motor. Am I wrong?

Thanks again for the help. I really appreciate it.

Scott
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: Did I kill my motor?

I've seen alot of these older mtrs like yours have the same problem. Sounds like yours blew a head gasket. Check your compression and if it's down do what Millies said and try it again. Re-check the compression after replacing the head gasket. If okay go and run it. Those older mtrs were pretty tuff.
 
Top