what now for 1973 evinrude 18hp

[stl]

Got this motor running over the weekend. It would run real rough for 6 or seven minutes then run pretty well after it warmed up. When I pulled the plugs the top plug was dirty and the bottom clean. I suspected water in the lower cylinder. i started the motor with the bottom plug removed and a fine mist of water came out. Is this a blown head gasket? How serious is this? Could it be something else? Maybe I missed something when I replaced the impellar. Is there something I should spray in the cylider in the meantime to prevent further damage while I figure out what ot do? Oh yea, compression is 100 on the top and 85 on the bottom. To me it sounds like I am screwed. All suggestions welcome.

 

[Molaker]

Re: what now for 1973 evinrude 18hp

Oh yea, compression is 100 on the top and 85 on the bottom. To me it sounds like I am screwed

To me it sounds like a blown head gasket. Pop it off and check. You will need a torque wrench to reinstall.

 

[iwombat]

Re: what now for 1973 evinrude 18hp

It's either a blown head, or exhaust gasket. More likely a head gasket.

Is it serious? Boy howdie, is it!

Gotta be fixed asap. Pretty easy one though.

 

[1730V]

Re: what now for 1973 evinrude 18hp

Classic symptoms of a head gasket.

Yes, an easy fix. By the way, the head bolt torque values are usually in inch pounds, not foot pounds. Make sure you know the difference.

 

[stl]

Re: what now for 1973 evinrude 18hp

I have an original service manual for this motor. Under Removal of Power Head From Exhaust Housing, it says to remove carburetor, leaf valve assembly, fuel pump, starter,flywheel, and magneto, befor you remove the seven hex screws that attatch the power head to the exhaust housing. Is all that necessary? I removed the power head on an old 5.5 johnson a few years ago on a water pump replacement. I know I did not do all that. Actually the 5.5 was pretty simple. I appreciate your patience on this. I really am gonna need some guidance on this. Also what about the water that has pentrated the cylinder now? Is there something I should do to prevent damage? Thanks

 

[iwombat]

Re: what now for 1973 evinrude 18hp

You should be able to remove the cylinder head with the powerhead in place. Exhaust cover gasket same thing. No need to remove the powerhead at all.

 

[stl]

Re: what now for 1973 evinrude 18hp

You should be able to remove the cylinder head with the powerhead in place. Exhaust cover gasket same thing. No need to remove the powerhead at all.

Oh i was way off. I will go look at the manual again Thanks

 

[iwombat]

Re: what now for 1973 evinrude 18hp

As for preventative measures w/ water intrusion. Make sure you wipe up any water you find and coat the inside of the cylinder walls with some twc3 outboard oil. Wouldn't hurt to spray some seafoam, WD-40 or any other aerosol lubricant into the intake ports of the lower cylinder, then crank it around a few times. Some water may have gone down in the lower main bearing and it'd be good to try and lube it up and push it out.

Best thing for it, is to complete your repair and run it a little. When you have your head off, look for signs of the leak. Post a picture if you can. If you can't see obvious signs of a leak you may just want to replace the exhaust cover gasket before running it again.

 

[freddyray21]

Re: what now for 1973 evinrude 18hp

hey stl where you at in St Louis? I am out in Manchester. Got a 58 18hp myself among others.

 

[Solittle]

Re: what now for 1973 evinrude 18hp

Make sure that you use a new head gasket and check to see if the head is warped. if it is take it to a machine shop and have it resurfaced ( don't let them remove any more than absolutely necessary). Torque the heads to spec and retorque after 10 hours or so.

 

[stl]

Re: what now for 1973 evinrude 18hp

hey stl where you at in St Louis? I am out in Manchester. Got a 58 18hp myself among others.

Fred check your pm i sent you one a little while ago.

 

[stl]

Re: what now for 1973 evinrude 18hp

This all makes good sense so far. It looks like the cois are mounted to the cylinder head. Can these stay intact during the repair? Other than a warped head is there anything else I should look for?

 

[iwombat]

Re: what now for 1973 evinrude 18hp

Again, you're going to want to find real evidence of where it blew so you know you found the problem. Other than the warped head, I say you've pretty much got it nailed.

 

[K.B]

Re: what now for 1973 evinrude 18hp

Good evening!!

Just took a look at your post and thought I'd give a couple of coppers worth.

Buddy of mine had the exhaust gasket blow on a 65 hp 3 cyl. doing the water out the plug hole. Had about the same diff. in the compression ratios. Head gasket was never touched 'cause it was spurting a STREAM of water out the plug hole. This meant to us that the head gasket was OK so that it would pump water. If the head gasket goes REAL bad, you won't get much, if any, water to pump out, as I have had experience with. Just a thought.