Surfacing Cylinder Head

[bob1340]

I have a '71 2 stroke Evinrude 18 HP 18012s with a warped head. I read where many folks re-surface these using a flat surface like a piece of thick glass and wet-dry sand paper. Do you suggest this or should I take it to a machine shop? How much would I be charged to have this done in a shop? Thanks, Bob

 

[Rick.]

Re: Surfacing Cylinder Head

No idea what a shop might charge. I use 120 grit and have never had a problem but I don't think mine have been badly warped either. Best of luck. Rick.

 

[F_R]

Re: Surfacing Cylinder Head

All it takes is a lot of scrubbing on the sandpaper. How much depends on how badly it is warped.

 

[bob1340]

Re: Surfacing Cylinder Head

No idea what a shop might charge. I use 120 grit and have never had a problem but I don't think mine have been badly warped either. Best of luck. Rick.

All it takes is a lot of scrubbing on the sandpaper. How much depends on how badly it is warped.

Thanks. I will give this a go tomorrow.

 

[kenmyfam]

Re: Surfacing Cylinder Head

Be methodical while doing it though and keep the pressure nice and even all over. That way you will make sure you don't end up with a ski slope on it.

 

[bob1340]

Re: Surfacing Cylinder Head

Be methodical while doing it though and keep the pressure nice and even all over. That way you will make sure you don't end up with a ski slope on it.

I think that is what I have, a slight ski slope! The previous owner had the head off at some point to repair a stripped spark plug. The area at the top of the head seeps water when it's running. It also had a compression leak between cylinders so it could be a compound ski slope. I am going to give it one try and if it does not fix the issue I may need to get a new head. I am wondering how much material I can safely remove before I have problems?

 

[mikesea]

Re: Surfacing Cylinder Head

how much you can remove will be avail in a book,but,what did people before do.I like taking a piece of marble and wrapping a piece of 100 grit around it,you can put your head in a vise(not your own yet)or get a couple pieces of wood and and piece of plywood to make a stationary holder for the head ,make a few passes on the head and look at where your shiny places are,you can then ,put a strait edge on it at the contact points ,you can then take a feeler guage and measure the warp.BUT,Id just make passes til the dip is out,I doubt it will be that much,

 

[bob1340]

Re: Surfacing Cylinder Head

how much you can remove will be avail in a book,but,what did people before do.I like taking a piece of marble and wrapping a piece of 100 grit around it,you can put your head in a vise(not your own yet)or get a couple pieces of wood and and piece of plywood to make a stationary holder for the head ,make a few passes on the head and look at where your shiny places are,you can then ,put a strait edge on it at the contact points ,you can then take a feeler guage and measure the warp.BUT,Id just make passes til the dip is out,I doubt it will be that much,

I used a marble cutting board with a sheet of thick glass on it. I don't have sand paper yet, but I was able to go around the edges with a feeler gauge. I can't quite get a .002 in the top of the head where the problem is so I am guessing I will remove about that much material. I "painted" the head surface with ink so I can see the high/low spots when I begin. I'll use some 150 or so grit to do this then cut with 80-100. I sure hope the power engine block is not warped, I doubt it. Of course I have to order a gasket as nobody carries parts for these old motors in stock.

 

[bob1340]

Re: Surfacing Cylinder Head

Hit it with lots of soapy water and 120 grit wet/dry in a figure 8 pattern. Once it got close I switched to 180 grit. Looks good now. I sure hope this works and fixes my issues. Hopefully the head gasket will come in tonight.

 

[bob1340]

Re: Surfacing Cylinder Head

Worked like a champ. The motor runs much better now. The compression is still low, but I figure being this thing has not run in almost 20 years the rings may not be seated. A couple hard pulls may get them where they need to be. But at least the compression is different in each cylinder now. It was 40/40 before and is 50/52 now. It was leaking cylinder to cylinder before.

 

[Rick.]

Re: Surfacing Cylinder Head

Glad it worked and I agree your compression is low. You might try a different gauge just to be sure. I would also recommended giving it a sea foam treatment. It may loosen up your rings enough to make an improvement. Rick.

 

[bob1340]

Re: Surfacing Cylinder Head

Glad it worked and I agree your compression is low. You might try a different gauge just to be sure. I would also recommended giving it a sea foam treatment. It may loosen up your rings enough to make an improvement. Rick.

Yep, I will do the Seafoam thing again. I did run it with a bunch in the gas and sprayed it in the carb, but the motor was running so bad it didn't really have a chance to do it's stuff. I'm thinking about taking 2 gas cans first run out. One with the regular mix and one with a seafoam mix.

 

[bob1340]

Re: Surfacing Cylinder Head

Well we put her in the lake today, first time in 24 years this boat got wet! Valco 14" aluminum. The motor ran smooth, but it would not power up correctly. Acted like it was at 1/2 throttle. Next outing I will try the seafoam again per instructions. If that does not unstick the rings I'll go into the motor and re-ring it.

 

[Rick.]

Re: Surfacing Cylinder Head

There could be a good reason for the half throttle feel. It could be running on one cylinder. They run smooth on one but lack power. Take a spark tester and make certain you have a very snappy blue/white spark that jumps 3/8's of an inch. Best to do it when it feels like your lacking power as sometimes the coils start good and fail as the temp. increases. Rick.

 

[bob1340]

Re: Surfacing Cylinder Head

There could be a good reason for the half throttle feel. It could be running on one cylinder. They run smooth on one but lack power. Take a spark tester and make certain you have a very snappy blue/white spark that jumps 3/8's of an inch. Best to do it when it feels like your lacking power as sometimes the coils start good and fail as the temp. increases. Rick.

I will do this. It has new coils, points, and condensers. But I will check it. Good time to build a tester. I have never seen one in any local auto stores.

Is there a particular procedure to follow doing this?

Do I pull the plugs and spin it with the starter?

Tank run the motor and check each cylinder separately?