1966 Evinrude 6hp Fisherman, Blown Cylinder?

[1riverrat]

While operating the motor at full speed it suddenly lost power. I did a compression check. The top cylinder was 90. When I pulled the lower sparkplug it appeared to be wet with water not fuel. A compression check of the lower cylinder was less than 30. Does it sound like this engine is done or can it be rebuilt?

 

[flintcreek]

Re: 1966 Evinrude 6hp Fisherman, Blown Cylinder?

By no means a expert, but before I said it was through I would check for a blown head gasket. That would cause low compression and might let water get in on top of the piston....Flintcreek

 

[Chinewalker]

Re: 1966 Evinrude 6hp Fisherman, Blown Cylinder?

Blown head gasket - almost positive. Water on the plug is a dead give-away... Should be able to fix it and be on your way for less than $10.00 (Sierra part number 18-2961, available right here on iboats). Part is also available at your local Johnson/Evinrude dealer.

 

[Lostfisher]

Re: 1966 Evinrude 6hp Fisherman, Blown Cylinder?

I would say bad head gasket.

 

[emckelvy]

Re: 1966 Evinrude 6hp Fisherman, Blown Cylinder?

I also vote for head gasket, it's a very common problem as the original gaskets did not have stainless steel "fire rings" reinforcement in the area where the gasket contacts the cylinder bores, and the gasket material is prone to blowing out.

The next step is to pull the head for inspection anyway, so you've nothing to lose.

Note that you should check the head for flatness. You can surface it yourself with sandpaper on a flat piece of glass to take out any low spots. Or send the head off to your friendly local machine shop for milling.

If you do replace the gasket, be sure to re-torque the head after the motor has been run and completely cooled down. It wouldn't hurt to re-torque again after about 20 hours running time.

Torque spec on the 1/4-20 head bolts would be around 70 inch-lbs. Apply a thin coating of water-resistant grease or Permatex #3 gasket dressing to the bolts to protect them from corrosion/seizure in the head.

HTH & G'luck..............ed

 

[1riverrat]

Re: 1966 Evinrude 6hp Fisherman, Blown Cylinder?

Thanks all for the quick replies.