Mercruiser 7.4L Intake Manifold

[mr300z87]

Hi All, its been a while since I have posted as my boat is running great. So my wife and I have acquired a 2nd boat/project, a Hurricane Sandy Victim which is a 1990 Sea Ray 250 DA Sundancer. Over all the boat's condition is great, she she took on some water during the Hurricane last fall and the engine is frozen, do not have the serial # at the moment but everything leads me to believe it to be original to the boat so lets say 89-91 year. I have just purchased a used 7.4L (serial # plate missing 95-96) I am told from a 96 boat, compression is good but did not hear it run as the carb is missing, which leads to my questions. The engine in the boat has the Rochester Carb with the spread bore intake manifold and the new engine has the square bore intake manifold for the Weber/Edlebrock/Carter style carb, can I just swap manifolds and run the Rochester? Or did GM/Merc change the heads (vortec style) like on the 5.7L. Also are there any other differences I need to be aware of. Both were set up for Bravo drives and the new engine includes fuel/raw water pump comb, Tbolt ignition, wiring harness and alternator. The frozen engine in the boat is 100% complete. Here is a picture in all her glory sitting on my friends trailer waiting to have her engine pulled.

As always any info is greatly appreciated.

Mike

 

[achris]

Re: Mercruiser 7.4L Intake Manifold

Manifolds are the same.... All the way from 1981 to the last of the 454s.... As you pointed out, square and spread is the only difference. And that's because Merc went to the Weber/Carter carbs.... In fact, if you try and order the older spread bore manifold, it supersedes to the newer square bore.

Chris.......

 

[mr300z87]

Re: Mercruiser 7.4L Intake Manifold

Thanks for the response achris, that was the answer I was hoping for. Wish me luck on this project. I am sure I will have many questions as I proceed.