4.3 oil leak when running after changing exhaust manifolds

[lr3guyjoe]

My cousin has a new to him deck boat with a 1996 4.3 MerCruiser in it. We ran the boat prior to changing out the exhaust manifolds and it ran great with no leaks.

My cousin replaced the manifolds and on the first test ride out the engine just seem to be dumping oil into the bilge. I wasn’t physically able to check the motor while running due to a pulled back at the time. But looking at as much as I could see from the top it didn’t look like it was coming from the front of the motor or the valve covers and a little bit of the block that I could see below the manifolds looked dry.

I wasn’t there when he did the manifolds he’s fairly mechanically inclined but not so much regarding engines. Is there something he could’ve bumped that would cause the motor to leak while running? The manifold swap seems pretty straightforward to me looking at the book.

I’m trying to do a little bit of armchair troubleshooting by asking you all because the boat is about an hour away from me and I plan to go look at it this weekend. Figured posting here first might give me some things to look for when I get out there, maybe it’s a common simple fix.

 

[Lou C]

Could be the oil pressure sending unit that is screwed into the rear top side of the block behind the intake manifold.

 

[achris]

Yeah, if the old manifold wasn't supported well enough during removal, it could easily have dropped down far enough and quick enough to have knocked the oil pressure fitting and cracked it.

The oil pressure fittings and sensors and sender is screwed into the block above the oil filter on those engines, NOT at the back of the valley, next to the distributor.

Chris....