1966 Evinrude Lightwin 3 HP Restore Questions

[boatnutty26]

So I came upon a 1966 Evinrude Lightwin 3 HP motor. It was actually thrown in as a "freebie" when I bought a 17' Grumman Scanoe on Craigslist. I am new to working on motors and am desperately trying to get it running.

I have been UNABLE to get it started and decided step 1 would be to do a compression test. When I initially did the test, I got a reading of 40 psi and 20 psi. I removed the cylinder head and determined the head gasket was extremely worn and somewhat rotted. I purchased and installed a new head gasket and re-tested. I now have a reading of 50 psi on the top cylinder and 20 psi on the bottom cylinder. It looks like the pistons are in decent shape but the cylinder head does have some rust on it. My first question is how can I get the compression up to where it needs to be? Also how can I tell if the cylinders or pistons are bad? I was told I might need to decarb it, but if I can't get it started, how do I do that? I can send or attach pics if that helps.

Please help! I love the idea of being able to restore a great old motor and hopefully use it for years to come. Any advice is much appreciated.

Thanks,
TD

 

[kfa4303]

Re: 1966 Evinrude Lightwin 3 HP Restore Questions

Hi boatnutty. Welcome to iboats. Great old motor you've got there. However, as you correctly noted, without proper compression it will never run. Low, or imbalanced compression is often due to a bad head gasket as you've noticed. However, there is a specific torque pattern as well as torque value that the head bolts must be tightened to. The head itself should also be resurfaced to help create as tight a seal as possible. If that doesn't do it, you may want to try a decarb by pouring a bit of SeaFoam, or similar product into the cylinders themselves and letting it sit for a few days, which should hopefully help free the piston rings a bit and improve the compression. Of course, it's a little motor so the compression will probably only max out about 50-60 psi. Here are some handy links that can walk you through a tune up from top to bottom.

3 HP Evinrude Johnson Outboard Tune-Up Procedure 1952-1967

Vintage Evinrude Johnson Outboard Parts & Diagrams - Catalog 278774

 

[HighTrim]

Re: 1966 Evinrude Lightwin 3 HP Restore Questions

What was the condition of the bore of the cylinders when you removed the head? Any noticable scratches or gouges?

If you dressed the head, and applied proper torque with correct sequence when changing the head gasket, you may need to dig deeper.

Remove the head, and measure the ID of the cylinder in numerous locations. It should be 1.5636"

The distance between the piston and the cylinder wall should be within .0013 to .002

If the rings are just worn out, it may be as simple as a re ring. The ring end gap is .005 to .015". Anymore on a new set of rings and you will need to go oversize.

 

[steelespike]

Re: 1966 Evinrude Lightwin 3 HP Restore Questions

Sometimes low compression is the result of stuck rings. Get something like Sea Foam and do a decarb treatment.
follow the directions on the container.
There have been a number of successes with this procedure.

 

[boatnutty26]

Re: 1966 Evinrude Lightwin 3 HP Restore Questions

Not sure if this helps, but here are some pictures of the cylinders and cylinder head. To me they look in-tact for the most part, but I am new to all of this, so maybe they need some work?

 

[HighTrim]

Re: 1966 Evinrude Lightwin 3 HP Restore Questions

You will need to clean and dress the head and block before installing the head gasket and torquing the head.

Use a piece of emory cloth, put in on something very flat like plate glass, and do figure 8s with it until it sands even. Ensure all the old gasket and sealer is removed. Torque the head to 60 to 80 inch/lbs in proper sequence. Ill post a pic to help with this. Start with your wrench at half (30inch/lbs), then 3/4 (45 inch/lbs), then the final 60 inch/lbs. The new head gaskets do not require sealer.

 

[HighTrim]

Re: 1966 Evinrude Lightwin 3 HP Restore Questions

 

[F_R]

Re: 1966 Evinrude Lightwin 3 HP Restore Questions

That motor should have 75-80 psi compression. There is something terribly wrong at only 20 psi. Remove the flat exhaust cover plate from the side of the cylinder block. You will then be able to see one side of the pistons and rings. No doubt the rings are hopelessly stuck. Poke at them with a small screwdriver and see if the move at all. They probably won't. You will be tearing it down for repairs.

I hope you cleaned that crud off the cylinder block gasket surface before installing your new gasket.

 

[boatnutty26]

Re: 1966 Evinrude Lightwin 3 HP Restore Questions

Again thanks to everyone for your helpful responses!

F_R, if the rings are stuck, would I need to just remove them and install new rings? Also, would this have caused damage to the cylinders?

I cleaned the crud as best I could, but there is still some that I can't seem to get off. HighTrim suggested emory cloth. Would that work by itself, or do I need a chemical or other cleaning agent? Would the SeaFoam get that off as well?

Sorry if these are dumb questions, but I am trying to learn as I go.

Thanks again, and as always, advice is greatly appreciated!

 

[HighTrim]

Re: 1966 Evinrude Lightwin 3 HP Restore Questions

If the rings are stuck, yes they are removed and replaced. Sometimes a decarb will help unstick them in certain situations. Pulling the bypass covers will determine if they are stuck or not. They should bounce when you push on them with a screwdriver.

The sandpaper/emory cloth is for dressing the head (sanding it true/straight). It will need to be cleaned first. Razor scrapers, solvents and the like will be needed to get it clean first.

 

[boatnutty26]

Re: 1966 Evinrude Lightwin 3 HP Restore Questions

OK, so here's an update.

Upon F_R's recommendation I removed the exhaust cover plate from the side of the cylinder block, and the rings are definitely stuck. I plan to go to Advance Auto tomorrow and get some SeaFoam. Hopefully that will solve the problem. I also purchased some emory cloth from Harbor Freight today and will work on dressing the head so I can re-install the gasket properly.

My next question is, if I can't free the piston rings with the SeaFoam, how do I remove the pistons to replace the rings? Do I need to take the entire power head assembly apart?

 

[HighTrim]

Re: 1966 Evinrude Lightwin 3 HP Restore Questions

Were all the rings stuck? Any of them have any bounce left to them?

To change the rings, yes you need to tear the powerhead down.

 

[boatnutty26]

Re: 1966 Evinrude Lightwin 3 HP Restore Questions

After further examination, it seems that the rings on the top piston do have some bounce left. One of the springs on the bottom piston has bounce and the second ring on the bottom is DEFINITELY stuck, no bounce whatsoever. I think I will try the de-carb first, and if that doesn't work, I guess I will have no choice but to tear the powerhead down. Hopefully I won't mess anything else up in the process!