1977 85hp electric low compression on port cylinders

[omcforever]

So after re-reading the entire thread, I take it you never initially replaced the head gasket with a new one?

[omcforever]

When I take off the exhaust port and look at the Rings, how do I know if they are stuck? Should I be able to move them?

If they are stuck ... What can I do to unstick them?

Transfer ports,,, not exhaust ports. Exhaust ports are under the big flat plate between cylinders on back of block.

[leckbass]

So after re-reading the entire thread, I take it you never initially replaced the head gasket with a new one?

I did not replace it, when I took it off I was surprised how good it looked. But if I can't find anything else wrong I will order a new one.

[leckbass]

Transfer ports,,, not exhaust ports. Exhaust ports are under the big flat plate between cylinders on back of block.

Is that the same as the bypass cover? Located under the starting solenoid on the port side

[omcforever]

Is that the same as the bypass cover? Located under the starting solenoid on the port side

Yes,,there are 2 on each side/one for each cylinder.

[leckbass]

I miked the cylinders, here are the numbers. The first set of numbers are from right to left and the second set of numbers are from top to bottom in each respective cylinder.

#2
Top L-R 3.3730 Top U-D 3.3730
Bottom L-R 3.3720 Bottom U-D 3.3720

#4
Top L-R 3.3710 Top U-D 3.3720
Bottom L-R 3.3740 Bottom U-D 3.3720

I removed the bypass covers and use a small screwdriver to push on each ring. The Rings all had "spring" to them. I was able to push each one of them in and out gently.

Here is a picture from the # 2


Here is a picture from the #4

[omcforever]

Are you using an inside mike/setting it up properly? According to your findings, the cylinders are shrinking vs getting larger based on OE bore of 3.375. Bottom one is egg shaped......re-check and compare to your manuals max specs/run out/taper but you appear to have too much taper/wear esp in the lower cylinder and concentricity is off as well.

[omcforever]

.010 and .030 is way too much taper and the holes aint round no more. Afraid the ole gal is worn out. (based on your readings/findings)

[omcforever]

Hard to seal a hole if it aint round and straight anymore.

[leckbass]

Are you using an inside mike/setting it up properly? According to your findings, the cylinders are shrinking vs getting larger based on OE bore of 3.375. Bottom one is egg shaped......re-check and compare to your manuals max specs/run out/taper but you appear to have too much taper/wear esp in the lower cylinder and concentricity is off as well.

I think I'm using it correctly...but definitely no expert here! I did take more than one measurement for each.

Yeah I guess it's kinda of hard for the cylinders to shrink after 42 years...

I will recalibrate the micrometer and give it another try this weekend.

[316jughead]

Do you have access to another compression gauge? 90 lbs is low for that motor, I think it should be around 115 to 120, maybe more when new but I don't remember. If your gauge is reading low, that would raise the 60 to 66 lbs up to maybe 85 to 90 and that might be OK to spend $45.00 on a gasket. That is still more than the 10 to 15 % but I've seen motors that look like yours run a long time. Is there significant scoring that does not show in the pictures? The rings don't seem to be stuck. Micing a cylinder isn't the easiest thing to do, you can do it. On E-Bay search omit the 0 on the P/N, you should get 5 results.

[leckbass]

Today, I'm fishing!

I am going to check the thermostat/vernatherms while everything is apart, put together a parts list, including head gasket, then put it all back together.

I do have another compression gauge, the old style that you have to hold in the hole, I'll give that a try.

[leckbass]

So far I think I need transfer port gaskets, head gaskets, and water deflectors

[leckbass]

Still waiting for the head gasket to come in, should I use Evinrude sealant on it?

[omcforever]

Lightly coat both sides of new cylinder head gaskets with OMC
Gasket Sealing Compound or equivalent.

[316jughead]

Lightly coat both sides of new cylinder head gaskets with OMC
Gasket Sealing Compound or equivalent.

Yep! When in doubt use sealer.

[omcforever]

Yep! When in doubt use sealer.

[omcforever]

I have done it both with sealer and not. On my motors, I insure the heads are flat/deck flat/head bolts cleaned and prepped and holes chased with a tap/proper sealers used in the proper place---priority number one and proper torque and torque sequence. Follow the the book..I say based on the info provided thru out the thread, squirt away,,,,

[leckbass]

All the parts came in yesterday. I replace the bypass gaskets as well as the head gasket. I also replaced the deflectors. Started the engine ran it for 10 minutes. Top of the port cylinder read 111 degrees after 10 minutes and the starboard cylinder was at 109 degrees after 10 minutes.

I ran the motor in the lake for 30 min. Then I retorqued the cylinder head bolts, compression is up to mid 70s. I used a different compression tester.

The one positive change was that when I pulled the spark plug off of the number 4 cylinder while the engine was running, I did notice a difference in RPMs.

I'm going to run it until it dies!