Blew it up yesterday, help determining the cause?

[Johndeere101]

The motor is a 1976 Johnson, I took it out yesterday and had it out for all of 5 mins and boom! Both sides of the block got blown out by the connecting rod cap. I know this because one side of the cap is scraped. Yet both rods are connected to both the pistons and crank. The crank is also still in place, no slop. Can somebody tell me what went wrong here??

 

[Xcusme]

Re: Blew it up yesterday, help determining the cause?

Gees, lets see....reasons?? There's possibly many reasons, age, wear, crummy rebuild, weak rod cap bolts, siezed bearing etc. Take your pick.<br />Sorry for your misfortune! If this is a new to you motor, who knows what may or may not have been done over the years maintenance wise.

 

[Joe Reeves]

Re: Blew it up yesterday, help determining the cause?

Normally caused by improper assembly or fouled carburetor.<br /><br />Fouled carburetor = lean fuel/oil mixture = improper lubrication = excessive friction= BOOM!

 

[Johndeere101]

Re: Blew it up yesterday, help determining the cause?

I understand what you guys are saying but this thing ran fine the day before without having any problems for atleast an hour. And then the next day this happens, and nothing even let go. The rod caps are still bolted to the rod and everything. But both sides of the motor got blown out, in line with the rod. It just doesnt make sence to me.

 

[Joe Reeves]

Re: Blew it up yesterday, help determining the cause?

If the rod caps are still bolted to the connecting rod, and they're in one piece, you have a broken crankshaft.

 

[Johndeere101]

Re: Blew it up yesterday, help determining the cause?

The crankshaft still seems to be solid. Can i figure out if that was the problem without having to rip the block apart?

 

[rayjay]

Re: Blew it up yesterday, help determining the cause?

I bet your big end needle brgs have abandoned you. <br /><br />Pull the head and see if any got caught leaving.

 

[Joe Reeves]

Re: Blew it up yesterday, help determining the cause?

Tear it down and be done with it.