Water in engine....twice!

[Ittledoo]

Hello everyone,
I'm new to this forum. I always use Powerboatparty.com. I'm hoping I can get some help over here also. I have a Brand new 454 roller motor.(500hp) I got water in it after 1/2 hr. last time due to cracked exhaust manifold. Found out after it was pressure tested, replaced it. This time I have 9 hrs on it and found water in it again!
Now a very short history of the situation. Professionally built; 90% sure it is not reversion; oil cooler, heads, manifolds, and risers have been pressure tested and are all good. Also I have external flaps on thru-hull exhaust. Brand new gaskets on the risers(factory mercruiser), but I only put copper high-temp silicone on the exhaust manifold. Which is what the engine builder said to do. I'm almost positive I did everything right. I was raised a gear-head by my dad. But that is in drag racing.
Any suggestions would be greatly appreciated. And I'm getting broke off this engine!

 

[fishmen111]

Re: Water in engine....twice!

Paul, I am sure the pros will kick in here shortly but in the meantime, need a little more information. Were both manifolds and risers replaced? They do not crack from use...they crack from freezing. Is the 454 the original block? Have you "straightedged" the heads and manifolds to eliminate warpage issues? If either the heads and/or block were with the cracked manifold if it did freeze, odds are they are cracked also.

 

[Ittledoo]

Re: Water in engine....twice!

Paul, I am sure the pros will kick in here shortly but in the meantime, need a little more information. Were both manifolds and risers replaced? They do not crack from use...they crack from freezing. Is the 454 the original block? Have you "straightedged" the heads and manifolds to eliminate warpage issues? If either the heads and/or block were with the cracked manifold if it did freeze, odds are they are cracked also.

One exhaust manifold was replaced and the boat has had nine motors. I'll double check the heads, the block and intake manifold are new. thx

 

[wca_tim]

Re: Water in engine....twice!

how much cam are you running? especially on overlap. 500 horsepower 454 is a good bit more than the factory version. It seems likely that you're getting water reversion from cam overlap and may need to go with longer risers (or extend yours)... you could also pick up some horsepower by going with afterarket manifolds and risers if you can score a set of imco's, emi's or stainless marine for a good price....

did your engine builder know you were goign to run factory exhaust risers?

on the sealer you put on the exhaust manifold, you're referring to the joint between manifold and heads?

 

[Ittledoo]

Re: Water in engine....twice!

how much cam are you running? especially on overlap. 500 horsepower 454 is a good bit more than the factory version. It seems likely that you're getting water reversion from cam overlap and may need to go with longer risers (or extend yours)... you could also pick up some horsepower by going with afterarket manifolds and risers if you can score a set of imco's, emi's or stainless marine for a good price....

did your engine builder know you were goign to run factory exhaust risers?

on the sealer you put on the exhaust manifold, you're referring to the joint between manifold and heads?

cam specs:
Duration @ .050 intake:230 Exhaust:236
Lobe lift intake .3610 exhaust .3580
Lobe separation intake 114

I'm not sure that my engine builder was concerned about the exhaust risers.
His forte' is ITPA/NHRA. So he is working w/ another shop in the Ozarks when building this engine. He did a blown 512ci. once....it came back with reversion.

And as far as the silicone, yes between the manifold and heads.

 

[Ittledoo]

Re: Water in engine....twice!

Also the boat came with a 330hp, 454. It did not have a thermostat. I'm thinking I need this, right?