cracked manifold question

[kcjefff]

Got a question about this. I have a 93 merc 4.3LX that has a cracked exhaust manifold. Correct me if I am wrong, but I am assuming that basically this manifold is the same as a car manifold, but with a water jacket around the outside to pass cooling water around and out. The crack I have is in the very outside, I am thinking this is the water jacket portion. Obviously I missed a drain plug and there was enough water in there to freeze it. I forgot the Anti-freeze.

I am definitely going to get the riser and manifold replaced, but it isn't going to happen before this weekend (our 4th of july weekend excursion). Does this crack indicate that I am possibly getting water in the engine via an exhaust port? I am hoping to be able to just patch with JB weld for the weekend to keep the boat from flooding/overheating, but don't want to risk hydrolock. I haven't used the boat yet this year, but I will check the oil when I get home to see if running with the muffs on was getting any water in there.

Any suggestions to not ruining our weekend vacation?

 

[tommays]

Re: cracked manifold question

Its a big risk for one weekend with and answere nobody can really give

tommays

 

[kcjefff]

Re: cracked manifold question

Does the fact that with my exhausts being separated(water comes out a hole in the transom, gas comes out the prop) I can tell there is no water coming out the gas exhaust matter?

 

[kcjefff]

Re: cracked manifold question

Also, is my understanding of the whole manifold/water jacket setup correct?

 

[Haut Medoc]

Re: cracked manifold question

That is basically the way it works.....
How is the exhaust gas separated from the water?
If it is cracked on the outside, it could be on the inside....
You will find out the hard way if it is.....
You could take it off & pressure test it, but then if you are going to do that you might as well replace it.....
Like Tom says....
Roll the dice.....JK

 

[AaronG]

Re: cracked manifold question

Why don't you just do it before the 4th? I did my manifolds and risers on fmy 5.7LX in like 2 hours.

Your power package is pretty common. Call around. someone probably has the manifolds/risers you need.

 

[boatgrunt]

Re: cracked manifold question

As others have said, I wouldn't recommend playing with fire. However, if you must, slap some JB Weld on what you think is only an exterior crack. Run water through the engine briefly using your muffs and then pull the plugs on the side with the crack. If you see water in the cylinders or on the plugs, you without doubt cannot use the old manifolds and now must act fast to get the water out of the cylinders. Turn the engine over, blow the water out and spray the inside of the cylinders with WD-40.

 

[RubberFrog]

Re: cracked manifold question

4th of July will be here next year. Will your boat?

 

[kcjefff]

Re: cracked manifold question

All good advice. If I buy it locally, I am looking at ~$300/manifold, if I order it online (and hence not have it by the weekend) I am looking at ~$400 for risers, manifolds, gaskets, and elbows for both sides. That is why I don't want to do it before the weekend.

I am basically looking for a way to know without a doubt that I cannot run it this weekend, such as what boatgrunt suggested.

 

[AaronG]

Re: cracked manifold question

Just wait to use it until its fixed.

 

[boatgrunt]

Re: cracked manifold question

Don't forget what Jammer18 suggested - a pressure test is actually the best way to go.

 

[Bondo]

Re: cracked manifold question

Your concept of How the Exhaust works is Close,......
Except that the Water,+ Exhaust Doesn't stay seperated to where they exit the boat......
The 2 Mix at the End of the Risers,.... That's Both Water,+ Exhaust you see coming out of Both, the Prop,+ the Holes in the Transom Shield........

As for Running them this weekend,........... Like Everybody Says,...... It's a Toss of the Dice,...... Are ya Feeling Lucky,..???????