Confused...

[nibs75]

So I posted last week about having a loss of power in my inline 4 Merc 140. I had seen water running down the side of the engine. After removing the manifold, I found a rather large crack in the block. Compression in each cylinder was ~130 and no water in oil. I ground down the crack, and jb welded it. I let it sit for 6 days, then put everything back together. Ran fine on muffs.

Took to the lake; again it ran GREAT! We were having a blast. things seemed "normal" boat was pulling hard and all was well. We ran around for 30 minutes or so, then anchored off and ate lunch. Swam for a while then ran around the lake some more. This time I was WOT, and the tach showed about 4k when I heard a pop. It kinda sounded like a backfire... then I lost power again. Not a total loss of power, but the boat is just not pulling hard and will only do ~ 20mph. I opened the engine bay and see water running down the engine again...

WTF? If this is only the water jacket that is cracked, why the loss of power? I can not seem to relate the symptoms (loss of power, slow out of the whole, lost 10-12 mph off WOT), with a cracked water jacket. If the compression was fine (before I even knew about the crack) and no water in the oil, then the crack doesn't appear to be internal.. Why the loss of power? I'm pulling it back apart tonight.

 

[Maclin]

Re: Confused...

What does the oil look like now?

 

[nibs75]

Re: Confused...

The oil is still the same. just black. needs to be changed ;-P but is not milky at all.

 

[rbh]

Re: Confused...

pull your plugs, it may be a coincident (bad spelling) but could one of the flappers let go and you sucked in some water?
rob

 

[nibs75]

Re: Confused...

I'll check when I get home. I'm gonna pull each plug and recheck compression on each cylinder again.

I just can't relate the cracked water jacket with lost performance. Especially when it was running great for the 1st hour when no water was leaking. Then we heard the "pop" (it sounded like a carb backfire), and the boat started to slow. When I looked there was water seeping again. I just keep going back to the fact that it ran fine with the hole patched... (Just so you know I am a test engineer. I test things and find the defects and workarounds for a living. While I am new to boating trouble shooting and problem solving are not new to me.)

Perhaps I am missing something very obvious to others.. If I get it all torn down tonight would pic help anyone? I can take pix of the crack...

 

[mkpj1]

Re: Confused...

I'd check compression again. bet you get a steamed clean plug. Your still able to hit 20mph probably only losing one cylinder into the exhaust which unlike a car, you can't look for foam in the antifreeze. Sounds like your block is fubar now. All it took was one warm up cool down cycle to crack the rest of the way into a cylinder. Hope for the best but really I think a tear down is required.

 

[nibs75]

Re: Confused...

Ok, this is really, really embarrassing - but I'm not too big to say I can be stupid!

When I got home from work I opened the engine bay and sat there for a minute. Decided to get started, so I unhooked the battery, was about to unhook the choke and breather tube when I noticed that there was a sparkplug wire laying loose... NO S$%^... I am a moron. cylinder 2, the end that plugs into the distributor cap was just laying there. I was so worried about the crack, and did see water seeping when I felt the lose of power (also the popping sound) that I let basic troubleshooting escape me.. I didn't check the wires..

I did pull that wire last week, and when I put it back it didn't feel quite as secure as the others. It still doesn't. The others are all real tight. anyway. Yeah, I lost a cylinder alright.. I'm just trying to get this boat to make it through this year, so hopefully it'll run ok when I take it out later this week to see.

It took me a minute to post that I really missed a very basic thing, but I did, and am sure others have as well. ;-p

 

[meals on reelsjello2]

Re: Confused...

dont swet it it happens to the best of us