exhaust manifold question

[chris0061]

I have a project boat I'm working on and I fired it up last weekend on the hose and there was a crack in the starboard side manifold. I shut it down and patched it with jb weld let it dry and started again. I let it run for about a hour and the temp only got to about 130. It is a 1981 Mercruiser 260 with the log style Manifolds. My question is will my patch hold and also I have a set of manifolds and risers off a 1985 260 that the risers come up out of the middle of the manifold instead off the aft end like the log style. The 85 manifolds are in excellent condition, what would it take to switch them out???????

 

[Bondo]

Re: exhaust manifold question

My question is will my patch hold

Ayuh,... Donno,... Roll the Dice,+ We'll find out...

Btw,.... Are you Sure there's No Cracks on the Insides,..??..??

what would it take to switch them out???????

Trying to plumb between the risers,+ the Y-pipes is the Problem....

 

[chris0061]

Re: exhaust manifold question

I'm not sure, I did not take it off. Will I be able to see or is there other signs of a crack on the inside. I do know that after running that long the oil still looks good if that has any tell, tell signs.

 

[Bondo]

Re: exhaust manifold question

or is there other signs of a crack on the inside.

Ayuh,...

A Hydro-Locked motor is a Dead Give-a-way.......

 

[chris0061]

Re: exhaust manifold question

can you explain what hydro lock is?????

 

[a70eliminator]

Re: exhaust manifold question

can you explain what hydro lock is?????

Water from a cracked manifold fills a cylinder and locks up the crankshaft because the pistons can't compress water.

 

[chris0061]

Re: exhaust manifold question

OK so if I ran it a hour on the muffs would it have hydro locked? If the manifold was cracked on the inside?

 

[a70eliminator]

Re: exhaust manifold question

Probably not, depending on the size of the crack it mignt not even cause an engine misfire, I think it's when your engine sits overnight with a cracked manifold full of water, then try and crank it, if water does come into the cylinder, it still can seep past the rings into the oilpan, so i don't really have a definate answer for you as it has never happened to me.

Bondo! help me I'm cornered.

 

[Bondo]

Re: exhaust manifold question

Ayuh,...

There are several scenarios that can play out,...
The fact that it ran for an hour is meaningless....

When it's shut down,...
As noted, it can fill a cylinder,+ Hydro-lock the motor,...
Or,...
The water might seep passed the rings into the base....
Or,..
Only some of the water seeps passed the rings,+ you try to Start it,...
The piston starts up the bore,+ Stops, Short because of the water, pushing the connecting rod Thru the block....
Or,...
Several more different possibilities....

'course,... None of them Good things,........

 

[chris0061]

Re: exhaust manifold question

I guess my best bet then would to replace both sides with the newer ones I have just to be safe. also I'll take the plugs out as I want to replace them anyway and crank it over before i put them back in. So to replace the log type manifold with the center type I should just need to get a pair of elbows right?