1976 Evinrude 75642D Water in Cylinder?

[StarTed]

I bought a 1976 75 hp Evinrude that the PO said needed a new head gasket since there was some light colored foamy stuff on the middle spark plug. This was last fall and I've been sitting on it ever since.

When I pulled the plugs I noticed a trace of tan colored stuff on the center cylinder plug that indicated to me that the PO was correct in that regard.

A compression check using an available deep cycle non starting battery showed all cylinders the same with a little over 100 psi.

I pulled the head anyway and found that the head gasket looked good with no evidence of leakage into any cylinder. However, there was no thermostat installed when I pulled its cover.

Could the moisture have been caused by operating it at a low temperature?

Could the middle cylinder not be firing properly and causing the moisture?

Are there any other causes that could be causing the moisture?

I don't think there was much moisture getting in but that information is no longer available to me. Here are some pictures.



Head with gasket just lying on it.



Head with gasket flipped over.



View of cylinders



Another view of cylinders



Low angle view of cylinders

I don't see anything that I would think would have been the problem.

Next steps?

I'm planning to replace the head gasket, thermostat kit, impeller, fuel pump kit, carburetors kits and spark plugs. Any other suggestions?

By the way, it has a jet pump on it so testing it in a barrel is out.

 

[F_R]

No Title

Put it back together with a new head gasket and run it to verify if it truly is getting water into the cylinder (it probably is). If it is ingesting water, the problem very likely is a warped exhaust cover plate, which lets water squirt past the gasket, and into the cylinder exhaust ports. Happens way too often on those motors. The plate warps at the slightest hint of overheating. And since the thermostat has been removed, it is reasonable to suspect somebody removed it in an effort to fix an overheating problem (wrong way to go). You are lucky you still have a motor. This problem normally totally destroys the powerhead.

 

[StarTed]

Thanks F_R for the information. I was thinking of removing the exhaust cover plate and taking a look in that side.

Now that I know that a warped plate could be the problem it seems just prudent to try to fix that before running the motor. The boat isn't quite ready to mount the motor on the transom so I have time.

How do I check for warpage? Is it flat enough to try sanding on a piate of glass?

 

[F_R]

If it has been leaking, you usually can see the bad areas as shown in the picture. You can further check it with an accurate straigtedge. The sanding trick is ok if it isn't too bad.

 

[StarTed]

Thanks F_R.

I appreciate your insight. I've done plenty of mechanic work, just not on an outboard.

I'll get some parts on order.

 

[StarTed]

Just an update.

I tore the engine apart and found an exhaust gasket missing a piece. I'm back to working on the boat between other things so the engine work has slowed down. Most of the parts and gaskets are in so I'll be back on the engine work again.

My plate is getting more heaped.

 

[StarTed]

I thought this might be the appropriate topic to add additional information about this outboard. It's a 1976 75 hp Evinrude.

I got it up and running and used it fishing on Roosevelt Lake when a problem arose.

While cruising back after fishing running near full throttle doing around 25 mph the power suddenly cut and left me running at 8 mph at wide open throttle. The engine sounded like it was at reduced throttle.

The engine ran smoothly and sounded like it was firing on all 3 cylinders.

I checked the portable fuel tank. It had plenty of fuel, the bulb was pumped and hard and the vent was open.

I limped back to the dock. It idled fine but being a jet the neutral wasn't quite right so it kept moving forward so I turned it off.

At home I opened up the engine and removed the spark plugs. They all looked about the same, nice and new.

I checked the compression and was surprised to find all 3 cylinders at 124 psi. The spark jumped strong and blue at over 3/8".

The linkage is all working normally and moves to full throttle as designed.

I have not checked fuel yet but the fuel pump was rebuilt and carburetors rebuilt.

Next I'll check for a decent flow of fuel from that portable tank.

This engine does not run on muffs because it has a jet unit. Testing it running will be difficult by myself.

Does anyone have any more ideas?

 

[StarTed]

Got around to checking the fuel pump pressure. It came up to 4 psi.

I guess I'll have to take it back out again to see if it works right now. Maybe something restricted the fuel at that time.

I can't think of anything else that could have caused the problem.

 

[StarTed]

Well, finally got serious about working on it again.

Pulled the carburetors and went through them again. They looked just fine. Added a fuel filter.

Took it back out on a lake and ran it again. It ran fairly good for about a mile then dropped back to 6 to 8 mph.

Took it back home and fulled the flywheel. Everything looked fine there. Strong spark on all 3 cylinders.

Took it back out and it wouldn't start.

Thought I'd call a shop and have them fix it. Found none of the shops in the area want to work on that old motor, especially since it has a jet pump. Was referred to a man named Paul in Spangle. Called him and he was willing to work on it but asked me to make some checks first. He made a comment about gaskets in the center over the high speed jets.

Pulled the flywheel and found the key flat in the crankshaft and out of the flywheel keyway. What a bugger to get that key out. Ended up drilling a 7/64" hole in the middle of the key and tapping it 6-32. Found a hard 6-32 screw but it still wouldn't pull so I cut a slot down the center of the woodruff key with a dremel grinding disk after covering everything in the area with paper towels. Then took a chisel and knocked the sides together. Screwed the screw back in and gave it a hard yank with a claw hammer and out it came. The crankshaft and flywheel look fine so I got a new key at ACE hardware and put it back together.

Took the carburetors back apart and remembering a comment Paul made I carefully checked for center gaskets in the carburetors. One carburetor was missing the gasket. That would allow it to suck air for high speed. Checked the thickness of one of the gaskets and found some thinner pieces of gasket material that was exactly half the needed thickness. I cut out 2 gaskets using an existing one for a pattern. I still don't know why it would run for a while before dropping out.

Took it down to Rock Lake for a spin. The wind made testing a challenge but I took it out for a run as much as I could.

It ran better than it has ever run for me. 26 MPH upwind and 29 MPH downwind. Remember, it's a jet pump, not a prop.

Finally another step ahead.

 

[racerone]

It is NOT a standard woodruff key.-------It might be best to install a factory key.-----Yes I know they cost more !

 

[StarTed]

It was not the cost but the availability. The key I got is not the standard one either because it has tabs at both ends to keep it out a given amount. It seemed to work well and torqued down fine. It took a little touching up with a file to get it seated properly but just at the corners. It's tight enough that it doesn't allow any movement but assembled as expected.

Thanks for the comment

 

[racerone]

The key is there to position the flywheel for proper timing.-----The flywheel is driven by the friction / clamping forces of the tapers.-----If you have that sorted out you are good to go..