357 mag bravo 4v long block replacement

[CravenRI]

Bought a boat with 2 357 mag bravo 4v sterndrives. First ride ran great, brought it back to the dock and left for the night. Came down the next day to find that the port motor had gotten water in the oil. Stupid me never checked compression before buying it and multiple cylinders were under 100. So now i need to repower and i'm looking to get a long block. So if i get a regular 350 325HP and bolt everything on, is it going to be compatible with the starboard 357? id like to save a few grand and go through the local guy ive gotten other motors from.

 

[alldodge]

The Merc 357 4V is a remanufactured 350 which has been bored. In short reman 350 vortec

 

[Scott Danforth]

dont forget the vanity cover with flames..... the 357 has the vanity cover with flames....

as AD mentioned, nothing special about the motor.

may want to check the exhaust manifolds, they may have leaked and simply rusted your valves

 

[CravenRI]

Those flames add at least 50 horsepower haha. I’d say the valves might have been a little rusted. I’m pretty sure he knew and changed the oil right before he started it for me. Motor only had 75 hours.

 

[Rick Stephens]

Personally, I'd want to know exactly why it has those problems before replacing the block.

 

[Scott Danforth]

you may just need new heads and exhaust.

my guess the exhaust is either leaking or the back of the boat is sitting low and needs taller risers under the elbows

 

[CravenRI]

Fair enough... boat And motor are getting hauled this week and I’m gonna go through it in my garage

 

[CravenRI]

you may just need new heads and exhaust.

my guess the exhaust is either leaking or the back of the boat is sitting low and needs taller risers under the elbows

Changed the exhaust when I was trying to save it. Still getting water in #8 cylinder

 

[alldodge]

Might just be a head gasket.

 

[Scott Danforth]

Changed the exhaust when I was trying to save it. Still getting water in #8 cylinder

measure the SWL to riser height. Riser should be 14" above the water line

 

[Rick Stephens]

measure the SWL to riser height. Riser should be 14" above the water line

Perfect timing before hauling.

 

[Lou C]

Yep that looks worse than my old heads when I had both HGs blown! If the cyls did not get rusted up you might able to save it with reman heads like I did.

 

[Scott06]

The bravo 357 mag is rated at 325 hp so I believe the long blocks are the same, but as mentioned you may be able to just get away with valave job and head gaskets.

if I haven’t you may want to check pricing at michigan motorz on long blocks and crate engines if u go that route. I had a nice experience there repowering 5 years ago.