what head gasket to use ?

KEVIN D TOBIN

Member
Jun 12, 2018
69
Boat Info
1993 290 sundancer, 7.4L mercruiser repower 2018
Engines
7.4L Bravo ll drive
I have a problem, I have a Mercruiser (this is a reman LONG BLK. with only one hour)(serial#0F021366) 1993 7.4L gen-v block and head (casting #10114182 is the block and #10114156 is the head) so I would say these are a matching set right ? Well, the water ports don't match and the gasket choice is even more confusing. But I think I have a grasp on it now, took alot of research thou, but I finally found the article that explains it. The water flow changed from mark-4 to gen-v, and although the ports don't match up here is the jist of it. On the gen-v although there is one hole at the front of the block that matches up with the head, it gets blocked off, the coolant comes up thru the block in between the cylinders and at the end it blocks off one and comes thru one, that is on a felpro #17042, this is the gasket that was on the engine when I took it apart.
Has anyone gone this deep into an engine before ? And do you think I am doing this correctly? I had the heads sent to a machine shop and they checked out ok. I plan on putting the heads and intake on and then pressure testing the water side with about 20 lbs. of air. Now the ? of sealants, all the head bolts go into the water jacket, manual #16 says to use perfect seal, when I took the head bolts out the threads were soaked, and what to use under the head of the bolt ? Should you or shouldn't you put sealant around each water passage ? Then there's the ? of the intake, should I plug the heat cross over (I have a electric choke) Should you use sealant on the water ports ? Seems like the more I look for answers the more confusing it gets. Well any help on this matter would be greatly appreciated, Thank You, Kevin
 

Attachments

  • coolant flow in block and heads mark-4 and gen -5.pdf
    360.8 KB · Views: 105
What was your reason for removing the heads on a remanufactured long block with only 1 hour on it?
Coolant in oil? Circulation/temp problems? Long blocks normally have a 1 year warranty that would be voided if you tear into it yourself.
 
What was your reason for removing the heads on a remanufactured long block with only 1 hour on it?
Coolant in oil? Circulation/temp problems? Long blocks normally have a 1 year warranty that would be voided if you tear into it yourself.
well after running it 2x I started to add the distilled water for the fwc system and when I turned on the electric inline water pump to burp the air out I noticed oil mixing with the water in the funnel, so I thought there was a blown head gasket, but NO, there wasn't, so I sent the heads out to get pressure tested and they were fine, so now I'm putting the heads and the intake back on and doing a pressure test on coolant side.
 
I have a problem, I have a Mercruiser (this is a reman LONG BLK. with only one hour)(serial#0F021366) 1993 7.4L gen-v block and head (casting #10114182 is the block and #10114156 is the head) so I would say these are a matching set right ? Well, the water ports don't match and the gasket choice is even more confusing. But I think I have a grasp on it now, took alot of research thou, but I finally found the article that explains it. The water flow changed from mark-4 to gen-v, and although the ports don't match up here is the jist of it. On the gen-v although there is one hole at the front of the block that matches up with the head, it gets blocked off, the coolant comes up thru the block in between the cylinders and at the end it blocks off one and comes thru one, that is on a felpro #17042, this is the gasket that was on the engine when I took it apart.
Has anyone gone this deep into an engine before ? And do you think I am doing this correctly? I had the heads sent to a machine shop and they checked out ok. I plan on putting the heads and intake on and then pressure testing the water side with about 20 lbs. of air. Now the ? of sealants, all the head bolts go into the water jacket, manual #16 says to use perfect seal, when I took the head bolts out the threads were soaked, and what to use under the head of the bolt ? Should you or shouldn't you put sealant around each water passage ? Then there's the ? of the intake, should I plug the heat cross over (I have a electric choke) Should you use sealant on the water ports ? Seems like the more I look for answers the more confusing it gets. Well any help on this matter would be greatly appreciated, Thank You, Kevin
You're on the right track. I believe that's the gasket I used on my Gen VI 454 when I built it for my 69 Camaro. The only thing I'm not sure of is whether or not it's marine grade.
As I'm sure you also read, you can use Mark IV heads on a Gen V and Gen VI with the right gasket. You should take a look over on www.offshoreonly.com. They have a lot more engine building knowledge over there. This attachment might help.
Gen 6 Gaskets.jpg
 
You're on the right track. I believe that's the gasket I used on my Gen VI 454 when I built it for my 69 Camaro. The only thing I'm not sure of is whether or not it's marine grade.
As I'm sure you also read, you can use Mark IV heads on a Gen V and Gen VI with the right gasket. You should take a look over on www.offshoreonly.com. They have a lot more engine building knowledge over there. This attachment might help.View attachment 93754
thank you so much hawk,yes I have read this , it was one of more informative reports that I found, I wish I had all this info before I bought this engine or for that matter before I bought this boat.
where you from hawk ? I'm in south jersey, Thanks again, Kevin
shoot me some info on how you added that attachment
 
thank you so much hawk,yes I have read this , it was one of more informative reports that I found, I wish I had all this info before I bought this engine or for that matter before I bought this boat.
where you from hawk ? I'm in south jersey, Thanks again, Kevin
shoot me some info on how you added that attachment
From or live? From 45 min west of Boston, but live in VA near Williamsburg. I would always suggest Gen VI over Gen V and even a Mark IV and a Mark IV over a Gen V if given the choice, but there's nothing wrong with a Gen V now that there is more knowledge and parts available.
The attachment was just a jpg picture taken from a pdf document I found on line years ago. You attach it using the Upload a File feature below your post.
 

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