1998 Mercruiser 5.7 Intake Manifold

[Bobdog234]

I have two 5.7 Mercruisers magmum motors that have edlbroke intake manifolds on them. Over the last two years they started to crack around the thermostats? I put some JB weld in the cracks that seemed to work for a while but I am still getting cracks. Has anyone had this happen

[Chris1956]

You might post on the I/O forum, as those sound like mercruiser motors.

[John_S]

Welcome to iboats.

Please post some pictures. If you are raw water cooled and boat in salt or brackish water, aluminum will get eaten away. The thermostat housing is typically were it is first detected. If it eats through the bottom part of the passage, allot of water will enter the crankcase in a very short amount of time, probably wasting your engine. For raw water cooled engines in salt/brackish water, intake should be cast iron or marine specified aluminum, which usually means bronze water passages.

[Bobdog234]

Thank you both for getting back to me. Looks like I will be replacing the intakes on my engines

[AZSenza]

Look for an intake like I have on mine, its a cast iron Z/28 marine piece, said to be the best bowtie manifold ever made. Very hi-rise. Mines a 97 Mercruiser 5.7 LXi 250 horse. Came stock with that intake and an adapter for the 7.4l TBI on top.
Very strange combo but shes fast. Can be found used all over for around 100 bucks. Yep its HEAVY and I was going to swap mine out for an Edlbrock till i saw the specs on it. p/n 14096242

[John_S]

Those cast-iron hi-rises are great intakes for standard head 350's. If he is running vortec heads that will not be an option.