Blew #2 Cylinder, what to look for?

[Numlaar]

Hey all,

Well if you have been following my posts lately, I am TRYING to get my boat in the water for the FL get together next week...

Two motors, and finally got one to work... 1976' 75HP Johnson.

Boat ran great for about 30 mins... (has rebuilt carbs, new gas tank, fuel pump, all new lines, link & Sync). Would take off out of the hole just fine. RPM would WOT at 5800.

While testing it out, it was zipping along around 5200RPM, (34MPH), and then it just died like someone cut the ignition...

Felt the cylinder heads, nice and cool... exhaust plate, nice and cool... the FLYWHEEL was VERY hot! almost too hot to touch, couldnt do a 1,2,3 count on it. So I am assuming something happened in the crank area.

I check the #2 carb, when I pulled the bolt for the high speed access, bowl was full of gas, re-checked the orifice and it flows nicely, pulled the carb, and the float is working perfectly, so I don't think #2 starved for fuel. Any idea what might have caused it to let go? It still cranks, just sounds funny, piston moves, but compression went from 135 this morning, to 30 now

Just want to know what to look for if I decide to rebuild it, as I don't want this to happen again.

 

[tashasdaddy]

Re: Blew #2 Cylinder, what to look for?

you want know anything until, you pull the cylinder head. may just be a blown head gasket.

 

[Numlaar]

Re: Blew #2 Cylinder, what to look for?

Ok I will give that a go...

Thanks TD.

and to answer your other question, no water in the cylinder when I checked compression.

 

[Numlaar]

Re: Blew #2 Cylinder, what to look for?

Well its not pretty....

#2 is DONE!!!

It looks at first glance like fuel starvation for that cylinder?? if you look at the bottom of the head at the other 2 cylinders, they seem wet compared to this one... that piston is gone... so is the cylinder wall, and the inlet into the piston chamber... it almost looks melted, one odd thing is the surface is "potted" where the air/fuel comes in... hard to describe but you can kinda see it in the picture.

 

[Numlaar]

Re: Blew #2 Cylinder, what to look for?

well I went through the carb again for #2 and I don't see anything wrong... float is good, bowl was full of gas, orifice was clean... boat was running great, no hesitation, nothing...

Anyone know what may have happened?

 

[tashasdaddy]

Re: Blew #2 Cylinder, what to look for?

you can definately see where #2 blew out,

 

[Numlaar]

Re: Blew #2 Cylinder, what to look for?

Indeed! Just trying to figure out why?

 

[Dhadley]

Re: Blew #2 Cylinder, what to look for?

What spark plugs are you using?

 

[Numlaar]

Re: Blew #2 Cylinder, what to look for?

It had L77JC4 Champions in it.

 

[Numlaar]

Re: Blew #2 Cylinder, what to look for?

Just trying to figure this one out before I start putting parts on the evinrude to get it running....

any theories on what caused it to blow? (this was a STRONG motor)...

 

[tashasdaddy]

Re: Blew #2 Cylinder, what to look for?

possible no tstat, water flows faster than it can disapate the heat, #2 is the center cylinder, and harder to cool.

 

[Numlaar]

Re: Blew #2 Cylinder, what to look for?

maybe... but I only ran maybe a gallon of gas through the Johnson before it blew...

I have run at least 8 gallons through the evinrude trying to sort out the hesitation/stall, and like I mentioned, when I went to steal the T-Stat from the evinrude, it didnt have one at all and it hasnt blown up yet!

The Johnson, I just took the plunger out of the middle, so it was just like an "open" t-stat, which still produced some restriction... I didn't completely remove it.

 

[Numlaar]

Re: Blew #2 Cylinder, what to look for?

Actually let me re-phrase the question...

The johnson would fire up barely bumping the key... not even one turn... the evinrude would fire up, but had to crank a little, so I was considering swapping out all the ignition parts...

DHadley asked me about the plugs, so i just want to be sure it wasnt caused by too hot of an ignition... I think you have been following my thread on my other motor that dies out at 2k RPM, and someone told me it could be the stator going... so I figured since I had the parts, it was worth a shot, but I just DO NOT want to blow the evinrude up too!!!!

So think it would be ok to strip all the ignition off this motor that blew and stick on another one??

 

[Numlaar]

Re: Blew #2 Cylinder, what to look for?

Oh just thought of one other thing...

In my testing, I have been running "heavy" on the oil... at least 32:1...

I used up that tank, and this was the first tank at 50:1... i know thats what the mix ration is "supposed" to be... but it seems awful weak to me... is it possible the mix could have caused this?

 

[spucky]

Re: Blew #2 Cylinder, what to look for?

If the ring gasket in center of the float bowl leaks air it can lean out severely by reducing the vac signal on the main jet.

 

[Numlaar]

Re: Blew #2 Cylinder, what to look for?

Ok thanks, I'll check it.

SO think I would be ok stealing the ignition parts for my other motor?