1973 25hp Evinrude Cylinder Head Removal

Hello, first posting on the forums - it has been an invaluable tool in getting my hands dirty with my first outboard!

Bought this motor for a 40oz of Colt 45 - much love for Detroit. Cleaned it up, recarbed, new impeller, etc., ran pretty good except at low idle. It died at full throttle on the water and I found that one of the spark plug threads is stripped (plug actually popped out). Going to try a Time-Sert myself, but I feel uncomfortable leaving the head on with the metal shavings and all...

Can I remove the head without cracking everything open? I bought the original manual (excellent tip from the forums here), and the instructions say to take flywheel off etc., but I'm just fixing up the head...

Is there anything else I should check out with the cylinder head off? Would like to clean up cylinders (seafoam spray? any tips?), and of course replace the gasket.

Thanks!
-Tom

Re: 1973 25hp Evinrude Cylinder Head Removal

If memory serves me correctly, you should not have to remove the flywheel to remove the cylinder head.

Re: 1973 25hp Evinrude Cylinder Head Removal

Just take the head bolts out. You'll need a new head gasket.

Re: 1973 25hp Evinrude Cylinder Head Removal

Resurface the head while it's off. Pretty easy job. Get a 18-24 inch square of glass for your work surface. If it's thin glass, like mine was, put the sheet of glass on a good marble cutting board. Use wet or dry sand paper in 120-150 grit. Fill a spray bottle with water and a little dish soap. Keep everything good and wet and move the head in a figure 8 pattern on the sand paper. You don't want or need a lot of pressure, just steady as she goes. It won't take long to do. Once you get close to having it perfect flat you will notice the head slides easier over the wet sand paper. And once done you can brag to everyone you resurfaced the head yourself. Don't let the wife see you walk out with the cutting board!

Another suggestion is to run a tap down all those head bolt bores. Don't cheap out, get new bolts and washers. Grade grade stuff is what you want and make sure and put a little anti-seize on the threads when you put them back in.

Torquing the bottom bolts may be an issue as you may not be able to get the torque wrench in there. It was like that on my 18 hp anyway. You will need to use a crow foot to get at it and adjust the setting accordingly.

Look at the cylinder bores real good for any scoring. If no scoring is present just clean what you can off the pistons while they are at the top. Oil every thing good before buttoning it up. Then once it is running good do the de-carb thing with sea foam.

Re: 1973 25hp Evinrude Cylinder Head Removal

Thanks for the tips! Pulled it off and scraping the old gasket off now (that old gasket hung on tight). A scratch here and there in the cylinder walls but it doesn't look too bad.

Resurfacing sounds like a cinch - will definitely do!

I'm going to take it to a shop to get the Helicoil put in, it's only a $16 job (I'm not much of a mechanic)

Took the thermostat cap off where two bolts snapped, I'll have to drill them out. I opened it up and - no thermostat! Kinda strange... perhaps it was running too cold and that was the source of my idle issues. One of the water holes was stuffed up with debris; hopefully the water jacket isn't all clogged up. Sprayed some canned air in there in hopes it will push anything in there out.

Thanks again!
-Tom

Re: 1973 25hp Evinrude Cylinder Head Removal

What Bob says about everything. specially the anti-sieze. Be sure that you remove the head. There was a thread a while back from a guy that left the head on and heli-coiled the plug hole- got debris jambed in the cyl and locked up the motor.

These are great motors and will run for ever.