71' evinrude fastwin 18hp head gasket troubles

Hey guys, Im new to the forum but Iv been searching for answers for my specif motor (71' Evinrude Fastwin 18) and haven't found a thread yet so Im hoping I can get a little guidance here. I recently had as issue where the expansion plug on the piston head cover came out, well today I replaced the plug and since it was the original head gasket I had to replace that too. Now so far the expansion plug is fixed but Im getting small water leaks in a few spots along the edge of the head gasket. I know I need about 18-20 ft lbs of torque for the head bolts but I do not know the correct tightening pattern so I assumed this might be the problem. Or could this be cause by some other issue like the head gasket not lining up correctly? Because the garbage can I have the motor running in has a lot of unburnt oil now and it seems like the exhaust is a lot more smokey than it was before I had any issues. Any help would be much appreciated.

Re: 71' evinrude fastwin 18hp head gasket troubles

Double check to make sure what the specific foot pound torque is for the 18 horsepower engine.

The sequence is:

9...10
5....6
1....2
4....3
8....7

Re: 71' evinrude fastwin 18hp head gasket troubles

+1 to what Joe said. Also when you had the head off did you check it to make sure it is flat? If not I would pull it back off and use some type of straight edge to make sure it is flat, if it is not you may not get it seal properly.

Re: 71' evinrude fastwin 18hp head gasket troubles

Im going to take the head back off today and check for flatness and re tighten the bolts in the proper order and see what happens. Hopefully that does the trick. Also I know the head gasket is labeled saying not to use any sealer but if the head isn't flat will it cause catastrophic failure if i do use some sparingly? And I know Im supposed to let it heat up and then re-torque the bolts but I haven't done that because it seems like a little water is getting into the cylinder or something so I didnt let it run for a real long time. What makes me think that is the amount of unburnt oil in the water after only a short time running and the exhaust seems much more thick. Im afraid of leaving it run like that, any suggestions?

Re: 71' evinrude fastwin 18hp head gasket troubles

HI Bay. I just diod the same job on my '66 20hp, which is the same as your motor. The unburnt oil in the water is perfectly normal for 2-strokes of this era. It will go away once you're on the open water. Whatever you do, do NOT use ANY sealant on the head gasket! Simply, lay it in place and tighten it down to the correct torque specs following the technique in the link below. However, you should ad a bit of high temp head RTV silicone, or similar product to the head bolts themselves. You'll want to start by tightening them down in stages; first 1/2 way, then 3/4, then the final value. You'll then want to run the motor for a bit and re-tighten the bolts one last time for good measure. If you're getting water into the cylinders, then the head bolts are probably not tightened down enough. You'll need a torque wrench to do the job properly as well.

http://forums.iboats.com/johnson-ev...-bolts-vintage-18-20hp-omc-motors-604338.html

Maintaining Johnson E & FD Serie

Re: 71' evinrude fastwin 18hp head gasket troubles

If the new gasket has a shiny appearance to it, that would be a factory sealer... do not apply anything to it. You'll probably see somewhere on it that states "use no sealer".

If the gasket is the older type, simply coat it with oil, nothing else.

The head that you state "isn't flat".... Hopefully the crankcase/block surface is not warped also. The head will be impossible to torque down properly due to the warping and will allow the combustion to enter the water passage areas which will result in having the combustion power flowing downwards while the water is trying to flow upwards... this results in a stalemate... the water can flow no further and just sits there and boils. And of course, water can find its way into the cylinders.

I would suggest that you find a sheet of glass which is flat, or some other surface that you know for a fact is absolutely flat... lay a sheet of "Black Wet Or Dry" #220 sandpaper on it... coat the sandpaper with some Mineral Spirits... then using your hand, move the warped surface of that cylinder head over the sandpaper in a figure eight rotation. Eventually that will restore the flatness of the head's surface. The figure eight motion assures that you aren't favoring any one certain area.

You can easily tell when you've went far enough in that figure eight motion simply by looking at the head's surface.

Re: 71' evinrude fastwin 18hp head gasket troubles

First I want to say thanks for all the input guys, Im a fisherman with more time than money so this guidance is invaluable right now. I just tried using a straight edge to check for warping but I think I am going to have to try that method, if I had to guess Id say there is a really good chance its not flat. I haven't put the head back on yet because I want to get it right this time so Ill try checking again. And I realize its a 2 stroke and an old one at that, its going to be a relatively smokey/oily motor, but Iv run it for about a year prior to my issues with no trouble and this just seems like thicker smoke and more oil discharge than usual it also doesn't idle very well either. Also is there any tell tale sign that water is leaking into the cylinder for sure?

Re: 71' evinrude fastwin 18hp head gasket troubles

BayHopper said:

Is there any tell tale sign that water is leaking into the cylinder for sure?

Click to expand...

Usually small traces of pure water would show up on the spark plug(s). If salt water, there would be very small BB like objects/traces on the plug electrode(s)

Re: 71' evinrude fastwin 18hp head gasket troubles

Ok well I went over it with a scotch brite pad for metal finishing because I thought maybe I didnt clean it off well enough and I used the correct torque pattern with a higher quality torque wrench than I had originally. It seems to be running better and there doesn't appear to be as much oil discharge or any water on the spark plugs. There is still a very very small water leak along the top edge of the head gasket but Im going to take it out for a short test run to see how it runs and then re torque the bolts, fingers crossed.

Re: 71' evinrude fastwin 18hp head gasket troubles

It takes that sealer on the head gasket a little time for it to seal. Take it out and run it and then re-torque.

Re: 71' evinrude fastwin 18hp head gasket troubles

Well everything seems to be fine, I took it out and ran it for a good 30 minutes. It runs well and the leaks have stopped. Thanks again for the assistance, you guys have helped restore my faith in humanity lol