1977 70 hp Evinrude Cylinder (Water)

Need a little advice on my 1977 70 hp Evinrude. It's been giving me fits starting at the ramp when the motor is in water. At home on the muffs it fires up easily. With the added backpressure, it seems to wear down the battery and does not want to fire at the ramp, then the battery dies. Today same thing, fired up at home on the muffs then went to the launch and did not start. Tried additional jumper box and no help. Before I left, I rasied the motor out of the water and it fired up. Put motor in water and it restarted ok after that. Went for a test ride and the only thing I noticed was that the top end speed was slow. Did not seem as fast as it should for a 70 hp. Carbs were rebuilt last year.

Diagnostic:

Started motor under muffs: pulled top plug - noticed slight rpm drop
pulled middle plug - noticed slight rpm drop
pulled bottom plug - no drop in rpm's (not firing?)
So motor was running on top 2 cylinders only.

Checked spark - all three have good spark

Checked compression - Top Cyl - 100
Middle Cyl - 105
Bottom Cyl - 125

Checked bottom cylinder and it has water blowing out sparkplug hole. (Basically motor is running on 2 cylinders). Not sure if water leaking adds to a compression reading?

Wondering if changing the cylinder head gasket and cylinder head cover gaskets will correct the problem. Any other items that would cause water to leak into cylinder?

Re: 1977 70 hp Evinrude Cylinder (Water)

I believe I've read that the water problem with some of the 3 cyl motors has to do with an exhaust gasket. Someone here will chime in with the correct diagnosis.

Re: 1977 70 hp Evinrude Cylinder (Water)

yes you have water coming into the exhaust port through the gasket , this is common thing with these motors especially if these motors are used in sea water i will show you how i solved the problem for good ,
http://forums.iboats.com/showthread.php?t=528873

Re: 1977 70 hp Evinrude Cylinder (Water)

Durban,

You're saying the two exhaust manifold gaskets should be replaced. The motor is a freshwater motor so I'm not too worried about salt corroding the ports. Was I off base thinking the cylinder head gasket would correct the issue?
0331917 0331916 Omc part numbers, correct me if I'm wrong.

thanks!

Re: 1977 70 hp Evinrude Cylinder (Water)

With the compression you have I'd have to go for the exhaust cover gaskets or plates.

Re: 1977 70 hp Evinrude Cylinder (Water)

I think I'm going to replace the cylinder head gaskets and the exhaust gaskets. I ordered the parts today along with a thermostat gasket. After taking off the head, I did see the accumulated water in the cylinder ports on the middle and lower cylinder. The bottom cyl was the worst and this was the one that was not firing due to the water. In order to get the exhaust cover off I had to drop the lower cowling to get at two of the lowest bolts. It slid right off after that and I had no frozen bolts to contend with. I'll be cleaning the surfaces while I wait for the gaskets to arrive. Do the gaskets require and gasket sealer?

Re: 1977 70 hp Evinrude Cylinder (Water)

I've always used 3-m 847 on the side cover gaskets as they have a tendency to want to leak. If the new head gasket says "use no sealer", don't. If not you can put OMC Gasket Sealing Compond on it.

Re: 1977 70 hp Evinrude Cylinder (Water)

For the gasket sealant I ended up using Permatex Aviation Gasket Sealer. I think it will work great on the exhaust plates. Finally got the exhausts and cylinder head back together. After letting it seal dry, I started the motor on the muffs and it fired right up. Sounded great and I checked the bottom cylinder for water. No water so the exhausts gaskets seems to be the issue and are working. Tested the boat on the water and I was surprised to see that I had only about 50% power on the lake. Hmmm, what next. The boat restarted and idled fine so I headed back to the ramp.

Trouble shooting process:

PUlled plug wires checking for dropped cylinder - Cylinder 3 was not working!
Coil - swaped coil wires for cylinder two and coil 3 did work on cylinder too so coil was not bad.
Spark on coil 3 - yes
Compression - 1 110 2 105 3 110 (That was a relief for a while I was thinking internal seal leak)
Fuel - since cylinder 3 was not working I took off that carb and inspected. Problem- stuck needle valve causing no fuel to cylinder.
Fixed needle and seat the set float level.
Tested on muffs - Engine roared on all three cylinders, did plug wire test and had a low drop on each so all are working.

Water test tomorrow. Strange how multiple problems exsisted at the same time, but it was nice findig out what the problems were. Also, don't forget how easily these motor run on one or two cylinders and you think they are running fine.