Where do I start the repair?

[imported_stump jumper]

I have a mid 90's carbureted 6 cylinder Mariner 135. The stream has always been kinda weak, even when the impeller was new. Today I was running the boat (with a potential buyer on board) and the carbs flooded out. We drifted a bit, got the boat fired up, and kept running. That is when the trouble started.

We were running with the cowling off and I noticed blue smoke coming from the head on the starboard side. Before I could get the boat shut down it was blowing blue smoke from what looked to be the head gaskets. The top end was very hot and cooked a couple wires. The head was so hot hat when I flicked water on it, immediately evaporated.

Now I am trying to evaluate the damage. Where do I start? The motor will turn over if I jump the ignition wires. It will not start with the key, won't even attempt. I would love to hear some input or ideas here. Have pictures of the head and will be a willing pupil. Please help me here.

 

[Lyle29464]

Re: Where do I start the repair?

use a jumper and run a compression test.

 

[imported_stump jumper]

Re: Where do I start the repair?

use a jumper and run a compression test.

Started that. When I use a jumper the prop is turning as the motor turns over. The top 2 cylinders/starboard side are 1. 25psi, 2. 35 psi. Is compression changed because the prop is turning?

 

[schematic]

Re: Where do I start the repair?

When I use a jumper the prop is turning as the motor turns over.

sounds like you have left it in gear....

 

[imported_stump jumper]

Re: Where do I start the repair?

Wow, it does sound like I left it in gear. It is 1am and I am headed outside to check.....ok, it was in gear and he key was on, so the battery is dead. Will charge in the morning and try again with compression check. Should compression be higher in neutral? Am I looking for a dramatic pressure differential between cylinders? What is an acceptable range for an older motor? There is a spring thing with a wire leading from the head to the......thing where wires connect. That spring thing is sprung and nearly burnt in two. What is it and will it keep the engine from starting?

Thanks for your help.

 

[Bosunsmate]

Re: Where do I start the repair?

if you can post a photo of it thatd be handy

 

[imported_stump jumper]

Re: Where do I start the repair?

http://i189.photobucket.com/albums/z55/jhalbrooks123/ee6688e6f084226a89d4de7d9237d414.jpg
http://i189.photobucket.com/albums/z55/jhalbrooks123/8d2bdd99ce9785f52df03d4b75af901e.jpg

 

[Chris1956]

Re: Where do I start the repair?

Remove all the spark plugs and after the battery has charged take the compression test. The actual reading is not important, but all cylinders need to be close in compression.

Post results. If the compression is good, you have dodged a bullet and need to rebuild water pump and replace thermostats and poppit valve.

 

[imported_stump jumper]

Re: Where do I start the repair?

Remove all the spark plugs and after the battery has charged take the compression test. The actual reading is not important, but all cylinders need to be close in compression.

Post results. If the compression is good, you have dodged a bullet and need to rebuild water pump and replace thermostats and poppit valve.

Is the poppet valve tied into ignition? Nothing happens when I turn the key. Cannot find any other burnt wires.

 

[imported_stump jumper]

Re: Where do I start the repair?

Ok, did the compression check? Don't know the cylinder layout, but compression is 60, 40, 60, 55, 85 and 0. I know this is a ridiculous question, but...What does that mean? Is the head gasket blown? Is the cylinder cracked? I am a bit out of my league here, just need direction.

 

[Bosunsmate]

Re: Where do I start the repair?

The photos look like a temperature sensor to me. If it is the cylinder head gasket blown thatd be the best outcome in my opinion. If it was me id be taking it off and inspecting the cyinders.
If you do that, check that the faces of the head and block have not warped by laying a flat level across them.
Also check all your fuses regarding the not starting problem. If you take it off post some pics and also pics of the bottom cylinder,

 

[Chris1956]

Re: Where do I start the repair?

What are the compression numbers on each bank of cylinders? None of your numbers are high enough to be in spec, but I suspect you have a lousy compression tester. You did crank the motor until the compression peaked, right?

 

[imported_stump jumper]

Re: Where do I start the repair?

What are the compression numbers on each bank of cylinders? None of your numbers are high enough to be in spec, but I suspect you have a lousy compression tester. You did crank the motor until the compression peaked, right?

Port side-top to bottom= 60,60,0
Starboard-top to bottom= 45,55,85
I cranked the motor till it peaked. The spark plug, from the cylinder with 0 psi, is pitted and beat up looking. There was some wires that burned up. I repaired them and now the motor turns over with the ignition. It has not started yet, but I have not tried very hard. Thanks for the continued help.

 

[boobie]

Re: Where do I start the repair?

Pull the heads and take a look inside.