Loud knock and engine lock up on start up...

[ktbarrentine]

Re: Loud knock and engine lock up on start up...

The mating surface of both elbow and manifold have been cleaned with a nuematic wire brush. So we are clean as a whistle. My Seloc repair manual says to put some gasket sealer on both sides of the gasket. Any thoughts???

My thoughts?....get rid of that worthless Seloc repair manual!!!

 

[Buck Naked]

Re: Loud knock and engine lock up on start up...

toolm8kr,
I just am at a loss why I only had water sucked back into the right bank of cylinders. Why did it not suck it back to the other side? did you have water in all your cylinders???

 

[RogersJetboat454]

Re: Loud knock and engine lock up on start up...

toolm8kr,
I just am at a loss why I only had water sucked back into the right bank of cylinders. Why did it not suck it back to the other side? did you have water in all your cylinders???

I don't know if I missed this in previous posts, but did you check the condition of the flapper valve in the exhaust?

 

[Buck Naked]

Re: Loud knock and engine lock up on start up...

My thoughts?....get rid of that worthless Seloc repair manual!!!

What would you suggest? I would think Mercruiser would sell one, wonder how much???

 

[Buck Naked]

Re: Loud knock and engine lock up on start up...

I just wanted to chime in on this one. I had the same thing happen to me last weekend. I was on the water and took my kid for a kneeboard ride. When i shut down the engine after his ride the engine did like a chuga chuga run on before dying. after that the motor would not turn over because it sucked up water from the exhaust into the cylinders and the water cannot be compressed during the compression stroke therefore it appears to be seized but actually it is not. nor are there any blown gaskets. I pulled the plugs and poured oil in and cranked the contamination out. I repeated until only clean oil was squirting out when cranking with no plugs. I put in new plugs and whammo! all good again. I would recommend trying that before barreling ahead changing gaskets unneccessarily. You will be opening a can of worms on a boat that old.

Cheers!

Yeah it turned into a cluster. But i feel good that all the rust and junk is outta there. I compression tested all the cyliders, ranged from 150 to 165psi. Fresh oil and filter and she fired right up. With the timing adjusted from 0 to 8 BTDC and the idle adjusted down to 750rpm the run-on problem seems to be a thing of the pass. I still want to inspect the exhaust shutters...

 

[ktbarrentine]

Re: Loud knock and engine lock up on start up...

What would you suggest? I would think Mercruiser would sell one, wonder how much???

Plenty of links available in these threads and from some of the more seasoned mechanics on the forum will provide you with free information / service manuals above and beyond what you get in either the Seloc or Clymer repair manuals.

Here is one link:
http://boatinfo.no/lib/library.html

(this is from the "adults only" sticky at the top of this forum - looks like you need to look at service manuals #7 and #14).

Best of luck!

 

[toolm8kr]

Re: Loud knock and engine lock up on start up...

Hey Buck,

I'm glad you got running again. To answer your question, yes I did have water in all cylinders. Also my oil got really milky and I changed it 5 times in a row (with the cheapest oil available) until it came out clear. I haven't had it out on the water yet. I'm going wednesday hopefully . If I still get water in there I am going to check the exhaust flappers as Jetboat 454 mentioned.

cheers.

 

[toolm8kr]

Re: Loud knock and engine lock up on start up...

I don't know if I missed this in previous posts, but did you check the condition of the flapper valve in the exhaust?

Where is the flapper located please? I thought there was one down near the exhaust bellows, and then some in the exhaust manifold. Is that correct? All my manuals and parts drawings just show the manifold as an assembly with no mention of shutters, and I've never taken it off to look for myself.

 

[toolm8kr]

Re: Loud knock and engine lock up on start up...

Oh I see now. They are in the top of the Y pipe.