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How far can I push a set of 7.4 heads???

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Old 06-02-2008, 09:50 PM
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Originally Posted by Plaineman
Thanks for all guys.... Strip, that motor was really bad man... I thought I had it bad but I realize a lot of people have a similar problem. I am probably in for a similar problem with these head bolts.... YIKES!!!

Hey Mobil, I did not see any pics of stainless steal risers but gotta ask... Eddie Marine is trying to sell me a performance upgrade with a set of cast aluminum manifolds with stainless risers... supposedly adds like 30 horse or something. They say it is safe and should last longer than stock... is this not true?

Chris, I have been looking and I am finding some cheap heads for this engine and may just try that... and the salt nuetralizer??? Will I find this at the local marine supply? I will give it a shot... thanks.

Looks like I will be keeping dry for a while... sux but gotta do what we gotta do.

Thanks....

B
Thats what suprised me the engine looked better than norm on the inside, I guess my buddy should of taking better care of the outside.It would of not rusted as bad.
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Old 06-02-2008, 10:56 PM
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Originally Posted by Strip Poker 388
Im missing something? the engine in the thread was a 415mpi 1996 stock exhaust.
Yes the risers in that pic was of a stainless risers. There are still a bunch in service. and still leaking in to the motors. Merc stopped using them thankfully.

The problem with stainless and stock cast iron is the gasket is in a hopeless battle dealing with corrosion problems from dissimilar metals. different expansion rates, and narrow surfaces separating water and exhaust.

All the aluminum manifolds I have seen pass water around the gasket surface not thru it and don't have a water weep problem.
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Old 06-02-2008, 11:35 PM
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Originally Posted by MOBILEMERCMAN
Yes the risers in that pic was of a stainless risers. There are still a bunch in service. and still leaking in to the motors. Merc stopped using them thankfully.

The problem with stainless and stock cast iron is the gasket is in a hopeless battle dealing with corrosion problems from dissimilar metals. different expansion rates, and narrow surfaces separating water and exhaust.

All the aluminum manifolds I have seen pass water around the gasket surface not thru it and don't have a water weep problem.
I see what your saying but this is the only pick of the manifold is see in my head bolt thread,Stainless risers?
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Old 06-02-2008, 11:44 PM
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Gotta admit I am missing something too... I did not see any stainless risers in those pics... maybe Mobil knows something we dont but they look stock to me. All of the stainless risers that I have seen are very distinct looking and in fact I argued with a guy trying to sell them to me that they would not fit in my boat... turns out they line right up to the stock 4" hose that goes to my captains choice exaust.

Anyway... I always knew this wasn't a poorman's hobby. If it were up to me I would be taking all the doe and putting down on the new 382 I want with the twin 700's. That one aughta be fun once chit starts to go south huh? Maybe next year...

Thanks again guys... really appreciate the help.

Brian
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Old 06-02-2008, 11:51 PM
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Originally Posted by MOBILEMERCMAN
Yes the risers in that pic was of a stainless risers. There are still a bunch in service. and still leaking in to the motors. Merc stopped using them thankfully.

The problem with stainless and stock cast iron is the gasket is in a hopeless battle dealing with corrosion problems from dissimilar metals. different expansion rates, and narrow surfaces separating water and exhaust.

All the aluminum manifolds I have seen pass water around the gasket surface not thru it and don't have a water weep problem.
So does this mean I should be good with aluminum manifolds and stainless risers??? That's what Eddie Marine is trying to sell me... supposed to work well but I may not be willing to try them on these heads.
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Old 06-03-2008, 11:33 PM
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Originally Posted by Plaineman
So does this mean I should be good with aluminum manifolds and stainless risers??? That's what Eddie Marine is trying to sell me... supposed to work well but I may not be willing to try them on these heads.
Thats what we put on this Scarab, he found a used set for 400,had to ad a angle plate to the riser to get it to line of with the transom.he only keep it 2 years after so I don't know they held up.I wouldn't think Eddie would be selling something that would be a potential prob? I dOnt have any experience with alum manifolds
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Old 06-04-2008, 12:02 AM
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Thanks Strip...

After a bunch of thinking on it today and some number crunching I have come to the conclusion that it is just time to repower this thing... I am looking at a nice 502 mag HO ready to go... a few tweaks here and there and she should be good as new. Probably not going to happen until next season but in the mean time I am going to find a cheap set of manifolds and see if I cant get a few more hours out of her this summer.

It will be fun to do the repower when the time comes though... thanks for the great post on the job you did on your friends boat... it helped a lot.

Peace.

Brian
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Old 06-04-2008, 08:32 AM
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Start a thread in the wanted section Ive seen some guys just give them manifolds, or atleast 200. but the freight will be close to the same

http://www.offshoreonly.com/forums/s...archid=2027144
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Old 06-04-2008, 08:37 AM
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Thanks man... I'm on it
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Old 06-04-2008, 06:39 PM
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Originally Posted by Plaineman
Thanks man... I'm on it
That being ,Going back and looking at the head surface I still don't think its going to seal.It would be easy while the exhaust if off to swap heads, find a set of good take off for now.
I am thinking even if you took the heads off, they machined down the gasket surface,nope. But if ya try it get a gasket that has the metal in it, like a Felpro and get some Black high temp, maybe it will fill in the holes when ya put it together,Goodluck
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